Journal articles: 'Gradient coatings'

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Szparaga, Łukasz, Przemysław Bartosik, Adam Gilewicz, Katarzyna Mydłowska, and Jerzy Ratajski. "Optimisation of Mechanical Properties of Gradient Zr–C Coatings." Materials 14, no. 2 (2021): 296. http://dx.doi.org/10.3390/ma14020296.

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One of the key components of the designing procedure of a structure of hard anti-wear coatings deposited via Physical Vapour Deposition (PVD) is the analysis of the stress and strain distributions in the substrate/coating systems, initiated during the deposition process and by external mechanical loads. Knowledge of residual stress development is crucial due to their significant influence on the mechanical and tribological properties of such layer systems. The main goal of the work is to find the optimal functionally graded material (FGM) coating’s structure, composed of three functional layers: (1) adhesive layer, providing high adhesion of the coating to the substrate, (2) gradient load support and crack deflection layer, improving hardness and enhancing fracture toughness, (3) wear-resistant top layer, reducing wear. In the optimisation procedure of the coating’s structure, seven decision criteria basing on the state of residual stresses and strains in the substrate/coating system were proposed. Using finite element simulations and postulated criteria, the thickness and composition gradients of the transition layer in FGM coating were determined. In order to verify the proposed optimisation procedure, Zr-C coatings with different spatial distribution of carbon concentration were produced by the Reactive Magnetron Sputtering PVD (RMS PVD) method and their anti-wear properties were assessed by scratch test and ball-on-disc tribological test.

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Szparaga, Łukasz, Przemysław Bartosik, Adam Gilewicz, Katarzyna Mydłowska, and Jerzy Ratajski. "Optimisation of Mechanical Properties of Gradient Zr–C Coatings." Materials 14, no. 2 (2021): 296. http://dx.doi.org/10.3390/ma14020296.

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One of the key components of the designing procedure of a structure of hard anti-wear coatings deposited via Physical Vapour Deposition (PVD) is the analysis of the stress and strain distributions in the substrate/coating systems, initiated during the deposition process and by external mechanical loads. Knowledge of residual stress development is crucial due to their significant influence on the mechanical and tribological properties of such layer systems. The main goal of the work is to find the optimal functionally graded material (FGM) coating’s structure, composed of three functional layers: (1) adhesive layer, providing high adhesion of the coating to the substrate, (2) gradient load support and crack deflection layer, improving hardness and enhancing fracture toughness, (3) wear-resistant top layer, reducing wear. In the optimisation procedure of the coating’s structure, seven decision criteria basing on the state of residual stresses and strains in the substrate/coating system were proposed. Using finite element simulations and postulated criteria, the thickness and composition gradients of the transition layer in FGM coating were determined. In order to verify the proposed optimisation procedure, Zr-C coatings with different spatial distribution of carbon concentration were produced by the Reactive Magnetron Sputtering PVD (RMS PVD) method and their anti-wear properties were assessed by scratch test and ball-on-disc tribological test.

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WANG, TAO, NING WANG, YANG LI, HAO WANG, JIE TANG, and YUNSHAN WANG. "STUDY ON PREPARATION TECHNOLOGIES OF THERMAL BARRIER COATINGS." Surface Review and Letters 24, no. 04 (2016): 1730004. http://dx.doi.org/10.1142/s0218625x17300040.

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Thermal barrier coatings (TBCs) is one of the main key technology for the high-pressure turbine blades which are the main components of the high-performance aerospace engines. It offers protection for underline metallic components from corrosion, oxidation and localized melting by insulating the metal from hot gases in the engine core. The properties and lifetime of TBCs are greatly influenced by the preparation technology, which includes plasma spraying (PS), physical vapor deposition (PVD) and laser re-melting (LM). In this paper, three technologies used to prepare the TBCs are reviewed. Resulting features of coating fabricated by each technology are also discussed such as: the porosity, the thermally grown oxide (TGO), the erosion resistance, the thermal shock and so on. Especially, it is pointed out that the performances of gradient coating and nano-coating are better than the traditional coatings. In addition, it is widely accepted that laser can be applied to re-melt the PS coating and even directly clad the gradient coating. In the future, the traditional preparation technology should be improved continually in order to enhance the coating lifetime, enhance the properties of coating and lower the cost of process. Moreover, the researches on gradient-nano-structured coatings preparation are absent and should be done with emphasis since the nano-structure and gradient structure can both benefit the lifetime and properties of coatings.

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Su, Ya Yu, Xiao Lei Li, Hui Jie Tang, Zhi Hao Zhao, and Jian He. "Thermal Shock Behavior and Bonding Strength of MoSi₂-BaO-Al₂O₃-SiO₂ Gradient Porous Coating with Polymethyl Methacrylate Addition for Porous Fibrous Insulations." Solid State Phenomena 281 (August 2018): 493–98. http://dx.doi.org/10.4028/www.scientific.net/ssp.281.493.

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In order to improve the thermal shock behavior of high temperature resistant coating on porous fibrous referactory insulations, the MoSi2-BaO-Al2O3-SiO2(MoSi2-BAS) gradient porous coatings were designed by preparing a dense surface layer and a porous bonding layer with the method of brushing and subsequent sintering at 1773 K. The porous bonding layer was obtained by adding polymethyl methacrylate (PMMA) as pore former. As the content of PMMA increases, the MoSi2-BAS coatings changed from a dense structure into a gradient porous structure. The interface bonding strength and thermal shock resistance of the MoSi2-BAS coatings were investigated. The result shows that the as-prepared coating with gradient porous structure exhibited excellent thermal shock resistance, which remained gradient structure without cracking after thermal cycling 100 times between 1773 K and room temperature. And the interface bonding strength of the gradient porous coating reached 1.5±0.08 Mpa, which was much better than that of the dense coating.

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Li, Chenchen, Xuefeng Yang, Shouren Wang, Yanjun Wang, and Jinlong Cao. "Preparation of WC Reinforced Co-Based Alloy Gradient Coatings on a H13 Mold Steel Substrate by Laser Cladding." Coatings 10, no. 2 (2020): 176. http://dx.doi.org/10.3390/coatings10020176.

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H13 die steel often fails as a result of physical and chemical effects such as wear, erosion and cyclic stress. Accordingly, the study evaluates Co-based gradient coating on an H13 steel featuring a stress-relieving effect. Scanning electron microscope and X-ray diffraction were used to analyze the microstructure and phase of the coatings. A microhardness tester and friction and wear tester were used to compare the hardness and wear resistance of the coatings and the substrate, and the wear morphology was observed. A pendulum impact test was used to compare the impact resistance of the coatings and the substrate, and the fracture morphology was observed. Finally, a corrosion test was used to compare the corrosion resistance of coatings and substrate. The results show that the Co-based gradient coatings have good combinations with the substrate, the hard phase content gradually increases from the bottom to the top of the coating, and the crystal microstructure generally maintains a distribution trend from coarse to fine. The hardness of the gradient coatings is significantly higher than the substrate, and from the coating surface to the substrate, the hardness decreases slowly. The wear loss of the coatings is much lower than that of the substrate, the main wear mechanism of the substrate is abrasive wear, and the main wear mechanism of the coatings is brittle spalling. While the gradient coatings increase the surface hardness, the brittleness also increases, the impact resistance of the coatings is lower than that of the substrate, the fracture form of the substrate is a ductile fracture, and the fracture form of the coating is a brittle fracture. The gradient coatings effectively improve the corrosion resistance of the substrate surface, and the higher the content of the reinforcing phase, the better the corrosion resistance of the coatings.

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Szparaga, Łukasz, Przemysław Bartosik, Adam Gilewicz, and Jerzy Ratajski. "Optimization of CrN/CrCN Gradient Coatings." Solid State Phenomena 237 (August 2015): 41–46. http://dx.doi.org/10.4028/www.scientific.net/ssp.237.41.

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The paper describes the optimization procedure supporting the designing process of geometry of gradient coatings basing on numerical simulation of internal stress and strain distributions in the coating and substrate. In mathematical model the gradient coating is represented by the so-called transition functions describing the change of physico-chemical parameters such as Young's modulus, Poisson's ratio, thermal expansion coefficient and the density as a function of the spatial variables. The object of optimization is system composed of a CrN/CrCN gradient coating and Cr interlayer between the CrN /CrCN coating and the steel substrate deposited on nitrided 4140 steel substrate. Decision variables are: the parameters of the of curvature of transition function , thickness of gradient coating and the thickness of the Cr interlayer. Optimization was carried out under pre-defined fixed continuous external loads and created decision criteria were the functions of the state of stress and strain in the coating and the substrate. Using the optimization procedure the sets of optimal parameters (Pareto sets) of the PVD gradient coating/nitrided substrate systems, due to the adopted decision criteria were determined. The analysis of the obtained optimal solutions (Pareto-optimal sets) was carried out using the "utopian solution method". It was also examined the technological stability of the Pareto-optimal solutions (nondominated) by analyzing the number of direct neighbors of these solutions in the decision variables space.

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He, Dai Hua, Qian Zhao, Chang Bao Wang, et al. "Sol-Gel Derived Gradient Biocoatings on Titanium Alloy." Applied Mechanics and Materials 80-81 (July 2011): 426–30. http://dx.doi.org/10.4028/www.scientific.net/amm.80-81.426.

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The bioceramic hydroxyapaptie (HA) is frequently used as coat in titanium medical implants improving bone fixation and thus increasing a lifetime of the implant. However, its joining to the titanium alloy is not satisfactorily good. The aim of this work is to produce TiO2and HA gradient coatings on Ti6Al4V alloy to improve the interface joining. Compared the microstructures of cross section of Ti6Al4V-HA coating and Ti6Al4V-TiO2/HA gradient coatings. HA coatings were obtained by sol-gel method with sol solutions prepared from calcium nitrate tetrahydrate and triethyl phosphate as the calcium and phosphorous sources. And TiO2 coatings were obtained from Tetra Butyl Titanate and absolute ethyl alcohol as the sources by sol-gel method too. The configuration and structure were investigated with scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The results demonstrated that the TiO2/HA gradient coatings have a homogeneous microstructure. The TiO2coating made the HA coating adhere to the Ti-6Al-4V substrate well.

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Ning, Cheng Yun, Ying Jun Wang, Xiao Feng Chen, Jian Dong Ye, Gang Wu, and Na Ru Zhao. "TEM Analysis on Bio-Functional Gradient Hydroxyapatite/ZrO₂ Coatings." Key Engineering Materials 336-338 (April 2007): 1676–78. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.1676.

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In the present study, bioactive functional gradient coatings were prepared using net-energy controlled plasma spraying technology. The microstructure and phases of the bioactive functional gradient coating were examined by means of transmission electron microscope, scanning electron microscopy and X-ray diffraction. The results revealed that: (1) as-sprayed coatings contained a large amount of amorphous phases and some nano-sized HA crystals formed during rapid solidification, (2) surface of the coating was very rough with different-sized micropores, and the gradient layer was much denser which firmly bonded to the substrate without gaps and obvious interface between the coating and the substrate

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Kolaklieva, Lilyana, Roumen Kakanakov, D. Chaliampalias, et al. "Mechanical, Structural and Thermal Properties of Multilayered Gradient Nanocomposite Coatings." Journal of Nano Research 17 (February 2012): 193–202. http://dx.doi.org/10.4028/www.scientific.net/jnanor.17.193.

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Multilayered, Gradient Tialsin-Based Nanocomposite Coatings Have Been Developed and Investigated with Respect to their Applicability in the Machining Industry. the Main Coating Layer Was Composed of 5-8 Nm Tin and Aln Nanograins. the Coating Possessed Hardness as High as 40 GPA, which Allows it to Be Classified as Superhard. during Heating up to 900oC in Air in Steps of 100oC for 6 H at each Temperature, the Coating Showed Good Stability up to 700oC. Thermal Treatment over this Temperature Caused a Decrease in the Hardness to Values Characteristic for Tialn Multilayered Coatings, while the Adhesion to the Substrate Remained Steady.

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Ratajski, Jerzy, Adam Gilewicz, Katarzyna Mydłowska, and Łukasz Szparaga. "Inter-Relationship between Coating Micro/Nanostructure and the Tribological Performance of Zr–C Gradient Coatings." Coatings 10, no. 11 (2020): 1121. http://dx.doi.org/10.3390/coatings10111121.

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The research presented in this article concerns Zr–C gradient coatings that were deposited on HS6-5-2 steel by reactive magnetron sputtering from the Zr target in appropriately programmed C2H2 mass flow rate, resulting in various profiles of atomic carbon concentrations in the coating and consequently in spatial change of the properties (H, E, …) and behavior (H/E, H3/E2, We). In particular, the characteristic changes in hardness and Young’s modulus in the Zr–C coatings represented approximately by the bell curve, which has a maximum at the content of about 50 at.% C, were an inspiration to study the behavior of gradient coatings with carbon content in the range of 0–50 and 50–85 at.% with the same hardness change profile. The obtained results indicate that, firstly, the gradient of spatial changes in the coating composition increases their resistance to cohesive damage in comparison to non-gradient coatings, and, secondly, the results show that high hardness is a desired property but not sufficient to ensure adequate coating performance. Independently, an appropriate nano/microstructural structure is necessary, which determines their tribological behavior. In particular, in the case of the tested Zr–C coatings, the obtained results indicate that gradient coatings with a carbon content in the range of 50–85 at.% have better properties, characterized by the critical force Lc2, wear, coefficient of friction, H/E and H3/E2 ratios.

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Zhang, Dong, Bao Ping Zhang, Zhi Ge Li, Lin Wang, Bin Liu, and Jin Qing Wang. "Biocompatibility of HAP/Ti Gradient Coating by Microarc Oxidation and Biomimetic Process." Advanced Materials Research 177 (December 2010): 325–28. http://dx.doi.org/10.4028/www.scientific.net/amr.177.325.

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This study is to evaluate the biocompatibility of HAP/Ti gradient coating by microarc oxidation and biomimetic process. Titanium alloys were activated by microarc oxidation (MAO), and immersed in simulated body fluid to prepare HAP/Ti gradient coating. Scanning electron microscopy (SEM) had been used to investigate the microstructure of the coatings. The biocompatibility of the coatings was evaluated by animal acute and subacute toxicity test, micronucleus test, hemolysis test, and oral mucosa test. The results showed HAP/Ti gradient coating was successfully fabricated on the substrate. The animal experiment showed the coating had not short-term toxicity, oral mucosa irritation, and micronucleus occurrence rate was 3.2 ‰ and hemolysis rate was 2.5%. The HAP/Ti gradient coating made by MAO and biomimetic process showed good bio-security and compatibility, it may be new oral implant materials.

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Zhu, Yousheng, Biju Zheng, Chen Hua, Hezhong Pei, and Peng Song. "Influence of Gradient Index and Pores on the Properties and Internal Stress of Continuous Transition Ceramic–Metal Coating." Coatings 12, no. 5 (2022): 569. http://dx.doi.org/10.3390/coatings12050569.

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Thermal-sprayed ceramic coatings are widely used in industry due to their favorable mechanical properties. However, traditional ceramic coatings are prone to failure due to the differences in physical properties between the bonding coating and the ceramic coating. In order to solve this problem, a continuous transition zone was introduced between the ceramic coating and the bonding coating, then air plasma spraying was used to prepare traditional coatings and continuous transition coatings. The Vickers hardness analysis results show that the existence of the continuous transition zone made the change of hardness between the ceramic coating and the bonding coating more gradual. To understand the stress distribution inside the continuous transition coating, models were established to express the interface between ceramic and metal in the continuous transition zone. Simulation analysis found that the existence of the continuous transition zone can significantly reduce the stress gradient inside the coating, and the gradient index of the continuous transition zone also has a great influence on the stress distribution inside the coating model. SEM (Scanning Electron Microscope) analysis found many pores inside the coating; modeling the pores and simulating the influence of pores on the internal stress of the coating showed that the existence of pores inside the coating can reduce the stress gradient at the interface.

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Rakhadilov, B. K., A. B. Nugumanova, P. Kowalewski, M. K. Kylyshkanov, L. B. Bayatanova, and D. N. Kakimzhanov. "Obtaining functional gradient coatings based on Al2O3 by detonation spraying." Bulletin of the Karaganda University. "Physics" Series 100, no. 4 (2020): 22–27. http://dx.doi.org/10.31489/2020ph4/22-27.

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The article deals with the phase composition and hardness of Al2O3 coatings obtained by detonation spraying. It was found that a decrease in the delay time between shots is leading to an increase in the hardness and elastic module of Al2O3 coatings. It was found based on X-ray diffraction analysis that the main reason for the increase in hardness with a decreasing in the delay time between shots is associated with increases in the volume fraction of α- Al2O3 phase. A high content of the more ductile γ-Al2O3 phase at the substrate-coating interface leads to an increase in adhesion characteristics, and a high content of the α-Al2O3 phase on the coating surface provides high hardness and wear resistance. The studies of X-ray diffraction presented that the highest phase content is achieved when the coatings are formed with a delay time between shots of 0.25 s. It was found that increase in the volume fraction of the α-Al2O3 phase is caused by the secondary recrystallization γ → α, which occurs due to the heating of particles during coating formation, i.e. due to increase in temperature above 1100 ºС in single spots of the coating when they are put each other

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Gou, Li, Ji Lei Zhu, Jun Guo Ran, and Suang Feng Yan. "Diamond Coated on Cobalt-Deficient Gradient Tungsten Carbide." Key Engineering Materials 280-283 (February 2007): 1889–92. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.1889.

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In order to improve the adhesion between diamond coatings and cemented tungsten carbide (WC-Co) substrates, the diamond coatings were deposited on one kind of cobalt-deficient gradient WC-Co by the microwave plasma chemical vapor deposition (MPCVD). Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were used to characterize the diamond coatings. The results showed dense, well facet diamond coatings. The cobalt content at the surface of substrate was measured by electron probe microanalysis. It was found that Co did not largely move to the surface as usual with deposition time increasing compared with the conventional tungsten carbide; The cobalt content at the surface of substrate after deposition (about 1 wt %) was lower than before (3.42wt%), which improved diamond coating’s adhesion against the tungsten carbide substrate.

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Makarov, A. M., T. I. Bobkova, A. F. Vasiliev, D. A. Geraschenkov, I. S. Prudnikov, and B. V. Farmakovsky. "Effect of gas phase composition on functional-gradient coatings formation by supersonic cold gas dynamic spraying." Voprosy Materialovedeniya, no. 1(93) (January 6, 2019): 65–69. http://dx.doi.org/10.22349/1994-6716-2018-93-1-65-69.

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The paper develops method for manufacturing wear and corrosion-resistant gradient coating. A special feature of the proposed method is the creation of chemical composition gradient due to controlled variation of the gas phase composition when applying supersonic cold gas-dynamic spraying. This ensures high adhesive strength of the composite coatings of the metal-non-metal system in combination with high micro-hardness of the peripheral layers. Such functional gradient coatings have wide practical applications.

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Kunioshi, Clarice Terui, Olandir Vercino Correa, and Lalgudi Venkataraman Ramanathan. "Gradient Nickel – Alumina Composite Coatings." Materials Science Forum 530-531 (November 2006): 261–68. http://dx.doi.org/10.4028/www.scientific.net/msf.530-531.261.

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Particle reinforced metal matrix composite (MMC) coatings have been developed due to property combinations such as increased hardness, high creep/fatigue resistance as well as superior wear and oxidation resistance. MMC coatings can be produced by various techniques, which include powder metallurgy (plasma spray and HVOF processes), liquid metal processes and electrodeposition. This paper presents the development of the electrodeposition process to obtain nickel-alumina composites. The process conditions were optimized and based on these gradient nickel-alumina composites were prepared. Microstructural characterization and hardness determinations were carried out. The effect of process parameters on the amount and distribution of alumina particles as well as morphology of the deposits with and without alumina gradients are presented and discussed.

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Fang, Ming Hao, Yan Gai Liu, and Zhao Hui Huang. "Microstructure and Corrosion Behaviour of Ni/Al-Al₂O₃ Gradient Ceramic Coatings on Q235 Steel." Key Engineering Materials 336-338 (April 2007): 2647–48. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.2647.

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Ni/Al-Al2O3 gradient ceramic coating was prepared on Q235 steel by plasma spraying. Microstructure and corrosion behavior in boiling 5%HCl solution of the samples sprayed with this coating were investigated. The results showed that thickness of Al2O3 ceramic coating was increased greatly and almost no connected pores formed in the gradient coating due to the existent of Ni/Al-Al2O3 transition interlayer coatings. The corrosion resistance of Q235 steel with Ni/Al-Al2O3 gradient composite ceramic coating in boiling 5%HCl solution was greatly improved.

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Zhou, Li Ming, Wei Gong, and En Ze Wang. "Analysis on the Residual Stresses in Functionally Gradient Fe360/Glass-Ceramic Coatings." Advanced Materials Research 717 (July 2013): 215–20. http://dx.doi.org/10.4028/www.scientific.net/amr.717.215.

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A novel functionally gradient composite was reported in this article. The composite material are composed of plain low carbon steel Fe360 as a substrate and glass-ceramics containing ZrO2 reinforcing particles as a coating. Based on a mathematical model of the residual stress, the geometric model and finite element analysis models of the Fe360/glass-ceramic gradient coatings were established. The residual stress of the gradient layers was calculated with the commercial software ANSYS 10.0. The results showed that the differences of thermal expansion coefficient and shrinkage rate in each layer resulting from the difference of the volume fraction of ZrO2 in each gradient layer could make the surface layer generate suitable compressive stress. The maximum residual stress presents itself at the interface between the substrate and the gradient coatings. The layer numbers and the thickness of graded coatings have a significant effect on the residual stress.

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Liu, Qi Bin, and Bang Cheng Yang. "The Bioactivity of Gradient Composite Bioceramic Coating with La₂O₃Fabricated by Wide Band Laser Cladding." Advanced Materials Research 668 (March 2013): 91–95. http://dx.doi.org/10.4028/www.scientific.net/amr.668.91.

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To improve the quality of bioceramic gradient coatings, wide band laser cladding technique was adopted to produce a kind of gradient composite bioceramic coating, which combines the good biocompatibility of HA and β-TCP with good toughness and strength of TC4 alloy. The rare earths oxide La2O3 was added to improve the properties of the bioceramic coating. The results indicate that when the adding of La2O3 is 0.6wt%, the ceramics coating is of the largest amount of HA and β-TCP catalyzed, and the number of cells proliferated and the ALP secreted on coatings is the biggest, which indicates that the biocompatibility and bioactivity of gradient bioceramic coating is the best. The biocompatibility and bioactivity are closely related to the amount of HA and β-TCP catalyzed by La2O3.

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Bobkova, T. I., A. F. Vasiliev, I. S. Prudnikov, and B. V. Farmakovsky. "Functional gradient coatings obtained by supersonic cold gas dynamic spraying." Voprosy Materialovedeniya, no. 1(97) (August 10, 2019): 74–78. http://dx.doi.org/10.22349/1994-6716-2019-97-1-74-78.

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The paper studies the development of a technology for obtaining a wear-resistant functional gradient coating during supersonic cold gas dynamic spraying. The process goes due to the variation of the composition of the gas phase in a heterophase flow. The coating has a high microhardness (up to 12 GPa) on the peripheral layers and wear resistance is 3 times higher than that of coatings obtained by traditional technology.

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Xi, Yuntao, Lin Wan, Jungang Hou, et al. "Improvement of Erosion-Corrosion Behavior of AISI 420 Stainless Steel by Ion-Assisted Deposition ZrN Coatings." Metals 11, no. 11 (2021): 1811. http://dx.doi.org/10.3390/met11111811.

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In this paper, a pragmatic technique has been developed to evaluate the erosion-corrosion behavior of three kinds of ZrN coatings (i.e., monolayer, multilayer, and gradient layers) which were deposited on AISI 420 martensitic stainless steel using an ion-assisted deposition technology. Among them, the monolayer coating refers to the coating with no change in composition and structure, the multilayer coating refers to the coating with alternating change of Zr/ZrN, and the gradient coating refers to the ZrN coating by increasing N2 partial pressure gradually. The morphology, composition, and microhardness of these ZrN coatings were examined by means of integrating the scanning electron microscopy (SEM), X-ray diffraction (XRD), and Knoop hardness measurements, while anodic polarization tests and salt fog spray tests in a simulated industrial environment have been performed to evaluate and identify the corrosion mechanisms of these coatings. The surface microhardness and corrosion resistance of the AISI420 martensitic stainless steel is found to be significantly improved by depositing the ion-assisted deposition ZrN coatings. The study indicates that the erosion-corrosion behavior in the slurry is the result of the synergistic effect of small-angle erosion and acid solution corrosion. Three ZrN coatings hinder the slurry erosion-corrosion behavior from two aspects (i.e., erosion resistance of small-angle particles as well as corrosion resistance of the substrate), thereby significantly improving the erosion-corrosion resistance of AISI 420 stainless steel. In addition, the ZrN gradient coatings show a much better erosion-corrosion resistance than that of the monolayer/multilayer ZrN coating because they have excellent crack resistance, bearing capacity, and electrochemical performance.

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Rakhadilov, Bauyrzhan, Meruyert Maulet, Madi Abilev, Zhuldyz Sagdoldina, and Rauan Kozhanova. "Structure and Tribological Properties of Ni–Cr–Al-Based Gradient Coating Prepared by Detonation Spraying." Coatings 11, no. 2 (2021): 218. http://dx.doi.org/10.3390/coatings11020218.

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In this paper, Ni–Cr–Al coatings were deposited using the detonation spraying method. The aim was to investigate how technological parameters influence coating structure formation, phase composition and tribological performances. We observed that the degree to which the barrel is filled with an O2/C2H2 gas mixture strongly influences the chemical composition of manufactured coatings. High degrees of barrel filling led to a decrease in aluminum content in the coating. Filling degrees of 40% and 50% produced sprayed coatings in which only Ni–Cr phases could be found. When the filling degree was reduced up to 25%, Ni–Al phases began to form in the sprayed coatings. Gradient Ni–Cr–Al coatings were produced by gradually reducing the filling degree from 50% to 25%. These coatings are characterized by Ni–Cr near the substrate level with Ni–Cr and Ni–Al phases at higher levels. The results obtained confirm that gradient Ni–Cr–Al coatings exhibit high hardness as well as good wear resistance.

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Wang, Yu, Qi Liu, Quansheng Zheng, Tianqing Li, Nanjing Chong, and Yu Bai. "Bonding and Thermal-Mechanical Property of Gradient NiCoCrAlY/YSZ Thermal Barrier Coatings with Millimeter Level Thickness." Coatings 11, no. 5 (2021): 600. http://dx.doi.org/10.3390/coatings11050600.

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The thermal insulation properties of thermal barrier coatings (TBCs) can be significantly improved with increasing the coating thickness. However, due to the weak bonding of high-thickness TBCs, the low reliability and short lifetime greatly limits their application under some severe operating conditions. In this study, a novel and high-efficiency synchronous dual powder feeding method is used to deposit a series of gradient NiCoCrAlY/YSZ coatings with millimeter level thickness. The tensile bonding strengths and residual stress state of coatings are evaluated in order to explore the effect of thickness on the bonding strength of coatings. The results suggested that, due to some micro-convex structure at the “GC/TC” interface and inside “GC” layer, the bonding strength of 1000-μm-thickness gradient NiCoCrAlY/YSZ TBCs with the 4:6 and 2:8 hybrid ratios is over 44 MPa compared to the common TBCs. The fracture position gradually shifts from NiCoCrAlY bond coat to NiCoCrAlY/YSZ transition zone and finally to the YSZ top coat owing to the different position of residual stress concentrations. After thermal cycling tests, the 1000-μm-thickness gradient coating exhibits a higher thermal cycling life. Some coarse cracks initiate and propagate at the bottom region of TBCs, which is mainly due to thermal expansion mismatch stress that finally results in the failure of the gradient coating between the “BC” layer and the substrate.

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Liu, Qi Bin, and Bang Cheng Yang. "Mechanical Properties on Gradient Bioceramic Composite Coating Produced by Wide-Band Laser Cladding." Key Engineering Materials 342-343 (July 2007): 681–84. http://dx.doi.org/10.4028/www.scientific.net/kem.342-343.681.

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To eliminate thermal stress during laser cladding and to raise the bonding strength between substrate and coating, composition gradient coatings are designed and fabricated by using wideband laser cladding technique on a Ti alloy. And mechanical properties on coating is studied. The experimental results indicate that the bonding strength between coating and substrate is fairly high, above 38.8MPa. The highest microhardness is obtained for coating containing 0.6wt.% Y2O3 1062HV0.1 and 1405HV0.1, respectively at bioceramic coating and alloyed transition layer. The average tensile strength, bending strength, and elastic modules of coatings are 767.83MPa, 1671.65MPa, and 13.98GPa, respectively.

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Chuppina, S. V. "Anti-Icing gradient organosilicate coatings." Glass Physics and Chemistry 33, no. 5 (2007): 502–9. http://dx.doi.org/10.1134/s1087659607050136.

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Szparaga, Łukasz, Piotr Myśliński, Adam Gilewicz, and Jerzy Ratajski. "Investigations on the Thermo-Mechanical Properties of CrN/CrCN Gradient Coatings Using a Thermo-Dilatometric Method." Solid State Phenomena 223 (November 2014): 100–109. http://dx.doi.org/10.4028/www.scientific.net/ssp.223.100.

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The paper describes issues related to the use of dilatometric methods for the study of thermo-mechanical properties of PVD gradient coatings. Tests were conducted on three types of CrCN / CrN coatings, which differed in the nature of the change of physico-chemical parameters in the gradient transition layer, deposited on a molybdenum substrate with the use of the cathodic arc evaporation method. The scope of the experimental studies included an analysis of the changes of the thermal “extortion” of the substrate – PVD coating system during annealing processes. In parallel, for comparison purposes, a mathematical description was proposed of gradient coatings containing the transition functions of material parameters. These functions describe the changes of such parameters as the Young's modulus, the Poisson's ratio, the thermal expansion coefficient, and the density as a function of spatial variables. Using the mathematical description proposed, numerical calculations of the state of thermal stress and strain for coatings are represented, respectively, by the transition function forms (a stepped, square, and square root) were carried via FEM. Based on the experimental and computational results obtained, the comparison between the elongation of the tested samples, and the state of thermal stress and strain in the substrate-gradient coating systems analysed were all specified.

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Ning, Cheng Yun, Ying Jun Wang, W. W. Lu, Xiao Feng Chen, Gang Wu, and Na Ru Zhao. "Microstructure and Mechanical Performances of Plasma-Sprayed Functionally Gradient HA-ZrO₂-Bioglass Coatings." Key Engineering Materials 280-283 (February 2007): 1893–98. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.1893.

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For practical applications such as artifical joints and dental implants, there is a strong demand for hydroxyapatite coatings with excellent performances to ensure long-term fixation. In the present study, functionally gradient HA-ZrO2-Bioglass coatings were prepared using net-energy controlled plasma spraying technology. The structural characteristics andmechanical performances of the coatings were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nanoindentation. The results showed that: (1) Pore sizes and compositions of the coatings changed gradually along the vertical substrate, crystal HA with few calcium phosphates was presented in the heat-treated coatings. (2) Surface of the coating was very rough with nano-sized crystalline grains and micropores; (3) Young’s modulus and hardness changed gradually at the range of coating-Ti6Alo4V interface. Compared with HA coatings, the tensile adhesive strength of the functionally graded HA-ZrO2-Bioglass coatings reached 38.6 MPa, much higher than that of single HA coatings.

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Meng, Xiang Cai, Xing Yi Li, and Tao Wang. "Effect of Electrodeposited Hydroxyapatite Coatings on Biomedical Titanium by Cathode Revolving." Key Engineering Materials 280-283 (February 2007): 1525–28. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.1525.

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The paper deals with a kind of new method of the electro-deposition on titanium by a cathode revolves. The depositing characteristic and mechanic were studied by scanning electron microscopy and X-ray diffraction. The experimental results show that the more fine uniformity and compact calcium phosphate bioactive coatings could be produced, compared with the conventional methods. The gradient Coating, which is fine inside and porous outside, could be obtained by controlling revolving velocity. The coating would transform to the hydroxyapatite after heat-treatment. After soaking in a simulated body fluid (SBF), nano-depositions were formed on the surface of the coating, then those particles would grow up needle-like, net-like, and an apatite-like layer could be observed finally. The gradient porosity coatings produced by cathode revolving electrochemical deposition would have high anti-dissolution and bioactive.

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Wang, Jiang Ting, Peter D. Hodgson, Jing De Zhang, and Chun Hui Yang. "Residual Thermal Stresses in a Fe₃Al/Al₂O₃ Gradient Coating System." Advanced Materials Research 32 (February 2008): 71–74. http://dx.doi.org/10.4028/www.scientific.net/amr.32.71.

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To combine the merits of both metals and ceramics into one material, many researchers have been studying the deposition of alumina coating using plasma spray on metal substrates. However, as the coatings are deposited at a high temperature, residual thermal stresses develop due to the mismatch of thermal expansion coefficients of the coating and substrate and these are responsible for the initiation and expansion of cracks, which induce the possible failure of the entire material. In this paper, the residual thermal-structural analysis of a Fe3Al/Al2O3 gradient coating on carbon steel substrate is performed using finite element modelling to simulate the plasma spray. The residual thermal stress fields are obtained and analyzed on the basis of temperature fields in gradient coatings during fabrication. The distribution of residual thermal stresses including radial, axial and shear stresses shows stress concentration at the interface between the coatings and substrate. The mismatch between steel substrate and composite coating is still the dominant factor for the residual stresses.

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Zhang, Yu, Zhanqi Cheng, and Hu Feng. "Dynamic Fracture Analysis of Functional Gradient Material Coating Based on the Peridynamic Method." Coatings 9, no. 1 (2019): 62. http://dx.doi.org/10.3390/coatings9010062.

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Functional gradient materials (FGMs) have tremendous potential due to their characteristic advantage of asymptotic continuous variation of their properties. When an FGM is used as a coating material, damage and failure of the interface with the substrate component can be effectively inhibited. In order to study the dynamic crack propagation in FGM coatings, a new method, peridynamics (PD), was used in the present study to simulate dynamic fractures of FGM coatings bonded to a homogeneous substrate under dynamic loading. The bond-based PD theory was employed to study crack propagation and branching in the FGM coating. The influences of the coating gradient pattern, loading, and the geometry and size of the structure on crack curving and propagation under impact loading were investigated. The numerical results show that different forms of the elastic modulus of graded material, the geometry of the structure, and the loading conditions have considerate effects on crack propagation in FGM coatings, but a specific form of elastic modulus had a limited effect on the dynamic fracture of FGM coating.

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Ning, Cheng Yun, Ying Jun Wang, Xiao Feng Chen, et al. "Research on Residual Stress and Surfacial Morphology of Bio-Functionally Gradient HA-ZrO₂–Ti Coatings." Key Engineering Materials 330-332 (February 2007): 1301–4. http://dx.doi.org/10.4028/www.scientific.net/kem.330-332.1301.

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In the present study, Functionally gradient HA-ZrO2-Ti coatings (FGC) on Ti6Al4V were prepared by the plasma spraying process. The residual stress and surfacial morphology of coating were studied by X-ray diffraction and scanning electron microscopy with an energy dispersive spectroscopy. The results showed that: (1) the residual stress of FGC is 72.1Mpa, much lower than that of single HA coating, (2) The surfacial morphology of the FGC showed typical characteristics of plasma-sprayed coating, no microcracks was observed because of its the thermal expansion matched between the gradient coating and substrate.

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CHEN, CHUANZHONG, DIANGANG WANG, QUANHE BAO, LIANG ZHANG, and TINGQUAN LEI. "SOLIDIFICATION MECHANISM OF LASER REMELTED BIOACTIVE HA COATINGS." Surface Review and Letters 12, no. 05n06 (2005): 819–23. http://dx.doi.org/10.1142/s0218625x05007682.

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In this paper, as-sprayed HA coatings were remelted by CW laser. The morphologies and the development of microstructures were analyzed by electron probe microanalysis. The solidification mechanism of laser remelted bioactive HA coatings is usually determined by the parameters of the temperature gradient G and the solidification velocity R. In the region of bottom pool, the G/R value is high which will result in the forming of planar crystal. With the decrease of G/R value, cellular and cellular dendrites will form. Near the surface, the coating can radiate heat to the atmosphere which will form a negative temperature gradient, consequently the structure is composed of dendrites.

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Baronins, Janis, Vitali Podgursky, Maksim Antonov, Sergei Bereznev, and Irina Hussainova. "Electrochemical Behaviour of TiCN and TiAlN Gradient Coatings Prepared by Lateral Rotating Cathode Arc PVD Technology." Key Engineering Materials 721 (December 2016): 414–18. http://dx.doi.org/10.4028/www.scientific.net/kem.721.414.

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TiCN and TiAlN gradient coatings were deposited on the AISI 316L stainless steel substrates by lateral rotating cathode arc (LARC) physical vapour deposition (PVD) technology. Corrosion and tribocorrosion behaviour was studied in 3.5 wt. % NaCl solution. The thickness of coatings was about 3 μm. For both coatings the corrosion potential shifted to more positive values as compared to the uncoated substrate. The corrosion current density decreased for TiCN and TiAlN coatings indicating up to 40 folds higher polarization resistance. The coefficient of friction value of TiCN coating is three times lower and durability is six times higher than that of TiAlN coating under the same tribocorrosion conditions.

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Tian, Tian, Bo Dang, Feng Ding, et al. "Study on the ZrN/Ag2O Micro–Nano Gradient Composite Structure Constructed on Pure Ti for Biomaterials." Coatings 11, no. 6 (2021): 677. http://dx.doi.org/10.3390/coatings11060677.

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Titanium and titanium alloys have been extensively utilized in biomedical implants due to their excellent comprehensive mechanical properties and biocompatibility. In this study, a ZrN/Ag2O micro–nano gradient composite structure was prepared on the surface of pure Ti by multi-arc ion plating (MAIP) technique and metal vapor vacuum arc (MEVVA) ion implantation technology. This study indicated that a dramatic improvement in performance in the surface hardness (~1800 HV0.1) was attributed to the presence of the ceramic phase (ZrN) with high hardness included in composite structure. The relatively low wear rate of gradient composite structure confirmed its excellent performance in abrasion resistance and the abrasion mechanism of gradient composite structure was mainly abrasive wear. After the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests, because of the synergy effect of ZrN micron coating and Ag2O nanoparticles, the ZrN/Ag2O gradient coatings indicated the highest free corrosion potential (Ecorr) and lowest corrosion current density (icorr) in Ringer’s solution, and the polarization resistances of multilayer coatings were greater than that of the substrate, exhibiting positive effects on retarding localized corrosion tendency. Additionally, the suitable dose of ZrN/Ag2O gradient composite coating can obtain antibacterial ability, which exerts no significant cytotoxicity and even excellent cytocompatibility over a longer service process. Furthermore, this study is conducive to design and develop for multifunctional coatings of implant materials.

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Zhang, Meng, Yong Ma, Jie Gao, et al. "Mechanical, Electrochemical, and Osteoblastic Properties of Gradient Tantalum Coatings on Ti6Al4V by Prepared Plasma Alloying Technique." Coatings 11, no. 6 (2021): 631. http://dx.doi.org/10.3390/coatings11060631.

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Plasma alloying technique capable of producing metallic coatings with metallurgical bonding has attracted much attention in dental and orthopedic fields. In this study, the effects of temperature and time of plasma tantalum (Ta) alloying technique on the mechanical, electrochemical, and osteoblastic properties of Ta coatings were systematically investigated. Ta coatings prepared at 800 °C possess better interfacial strengths than those prepared at 750 and 850 °C, and the interfacial strength increases with prolonged alloying time (30–120 min). At 800 °C, however, the increased proportion of the soft Ta deposition layer with alloying time in the whole coating impairs the surface mechanical properties of the entire coating, as convinced by decreased microhardness and wear resistance. Moreover, Ta coatings exhibit better corrosion resistance than the Ti6Al4V substrate in Dulbecco’s modified Eagle medium. The enhanced adhesion and extracellular matrix mineralization level of osteoblasts demonstrate the better cytocompatibility and osteogenic activity of the Ta coating. Ta30 (Ta coating prepared at 800 °C for 30 min) exhibits excellent mechanical, electrochemical, and osteoblastic behaviors and is promising in biomedical applications.

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Huo, Yan Li, Yu Feng Chen, Jie Tang, Hai Lin Liu, and Chun Peng Wang. "Fabrication of Multiple Oxidation-Resistant Coating on C/SiC Matrix." Advanced Materials Research 105-106 (April 2010): 406–8. http://dx.doi.org/10.4028/www.scientific.net/amr.105-106.406.

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Oxidation-resistant coatings with gradient structures on C/SiC composites were fabricated. The gradient oxidation-resistant coatings were composed of three layers. The inner layer was reaction-bonded SiC which was fabricated by silicon infiltration. The middle layer was dense CVD SiC with the gradient component which was produced by the pyrolysis of methyltrichlorosilan (MTS) in excess hydrogen. The outer layer was a sealed layer with B4C and MoSi2 powders which was fabricated by slurry process. Optical microscope and SEM were used to observe the cross-section morphology and microstructure of coatings. XRD and EDS were used to characterize the phase composition and component distribution of coatings. EDS analysis showed the component distribution of CVD SiC coating changed significantly with the change of ratio of MTS to H2. The result indicated that C/SiC composite had good oxidation resistance when it was used at high temperature in the environment of high-speed combustion gas.

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Żukowska, L. W., A. Śliwa, J. Mikuła, et al. "Finite Element Prediction for the Internal Stresses of (Ti,Al)N Coatings." Archives of Metallurgy and Materials 61, no. 1 (2016): 149–52. http://dx.doi.org/10.1515/amm-2016-0027.

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The general topic of this paper is the computer simulation with use of finite element method (FEM) for determining the internal stresses of selected gradient and single-layer PVD coatings deposited on the sintered tool materials, including cemented carbides, cermets and Al2O3+TiC type oxide tool ceramics by cathodic arc evaporation CAE-PVD method. Developing an appropriate model allows the prediction of properties of PVD coatings, which are also the criterion of their selection for specific items, based on the parameters of technological processes. In addition, developed model can to a large extent eliminate the need for expensive and time-consuming experimental studies for the computer simulation. Developed models of internal stresses were performed with use of finite element method in ANSYS environment. The experimental values of stresses were calculated using the X-ray sin2ψ technique. The computer simulation results were compared with the experimental results. Microhardness and adhesion as well as wear range were measured to investigate the influence of stress distribution on the mechanical and functional properties of coatings. It was stated that occurrence of compressive stresses on the surface of gradient coating has advantageous influence on their mechanical properties, especially on microhardness. Absolute value reduction of internal stresses in the connection zone in case of the gradient coatings takes profitably effects on improvement the adhesion of coatings. It can be one of the most important reasons of increase the wear resistance of gradient coatings in comparison to single-layer coatings.

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Azari, Rezvan, Hamid Reza Rezaie, Alireza Khavandi, and Elham Malek Mohammadi. "Effect of Gradient Layer of TiO₂- HA on Properties of the Ha Coated Ti-6Al-4V." Defect and Diffusion Forum 400 (March 2020): 193–200. http://dx.doi.org/10.4028/www.scientific.net/ddf.400.193.

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The use of hydroxyapatite (HA) coating on metallic implants has always been a challenge due to a discrepancy between ceramic coating and metallic substrate properties. In this study, functionally graded TiO2-HA coating (FGC TiO2-HA), with bottom-up composition: 100% TiO2, 50% TiO2 -50% HA, 100% HA, produced by sol-gel method on the Ti-6Al-4V alloy substrate. The XRD, FTIR and DSC results signified desired phase achievement. The quality assessment and scratch resistance of FGC TiO2-HA in comparison with control samples (single-layer HA and double-layer TiO2-HA coatings) were assessed by SEM and FESEM images and nanoscratch test. According to the tests outcomes, The TiO2 intermediate layer increases the HA coating’s strength (22%) and surface hardness, while gradient layer of TiO2-HA improves (14%) this consequence by progressing the coating integrity.

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Chang, Shiun Wei, Chun Ming Chen, and Ju Liang He. "Power Modulated Plasma-Polymerized Gradient Anti-Fingerprint Transparent Protective Coating with a Gradient Composition." Advanced Materials Research 509 (April 2012): 135–37. http://dx.doi.org/10.4028/www.scientific.net/amr.509.135.

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Polymeric materials have been widely used as flexible substrates and housing parts of modern electronic wares. However, their low hardness and scratch resistance must be improved by additional protective surface coatings, which require not only mechanical durability but also additional functions such as surface hydrophobicity, oleophobicity as well as anti-fingerprint performance. To satisfy these, a power modulated plasma polymerization technique was designed to synthesize a transparent compositional gradient coating on polycarbonate (PC) substrate. Firstly, a constant flow rate of tetramethyldisiloxane (TMDSO) precursor was introduced where higher plasma power was employed to deposit a hard H-C-Si-O bottom layer. The plasma power was then decreased meanwhile admitting increased fluoromethane (CF4) gas flow as the second precursor to obtain a top layer with low surface energy. The hard bottom layer acts as a strong mechanical support and the top layer gives additional hydrophobicity and oleophobicity. Ultimately, the coating shows that a pencil hardness of 3H and Scotch-tape adhesion of 5B improves its protective function. A water contact angle of 105° and oil contact angle of 31.7° can be obtained. The coated specimen remains an optical transparency of 90% close to bare PC material. Comparing with commercialized screen protectors, the developed coating shows superior protective and anti-fingerprint performance.

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Fuentes, G. G., M. J. Díaz de Cerio, J. A. García, et al. "Gradient CrCN cathodic arc PVD coatings." Thin Solid Films 517, no. 20 (2009): 5894–99. http://dx.doi.org/10.1016/j.tsf.2008.08.005.

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Suvorov, D. V., G. P. Gololobov, A. B. Tolstoguzov, et al. "Electrodeposition of Ni-W gradient coatings." Journal of Physics: Conference Series 857 (May 2017): 012047. http://dx.doi.org/10.1088/1742-6596/857/1/012047.

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Manaila, R., A. Devenyi, D. Biro, L. David, P. B. Barna, and A. Kovacs. "Multilayer TiAlN coatings with composition gradient." Surface and Coatings Technology 151-152 (March 2002): 21–25. http://dx.doi.org/10.1016/s0257-8972(01)01633-4.

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Fuentes, G. G., M. J. Díaz de Cerio, J. A. García, et al. "Gradient CrCN cathodic arc PVD coatings." Surface and Coatings Technology 203, no. 5-7 (2008): 670–74. http://dx.doi.org/10.1016/j.surfcoat.2008.08.079.

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Kim, J. H., and Y. J. Lee. "Optimization of Gradient-index Antireflection Coatings." Journal of the Optical Society of Korea 4, no. 2 (2000): 86–88. http://dx.doi.org/10.3807/josk.2000.4.2.086.

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Hur, Sung Kang, Sang H. Yoo, Joanna R. Groza, Jung Man Doh, Kazuo Yamazaki, and Kazuo Shoda. "Graded coatings by gradient temperature densification." Journal of Materials Research 13, no. 5 (1998): 1255–59. http://dx.doi.org/10.1557/jmr.1998.0179.

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Functionally gradient materials (FGM) were prepared using layers of ZrO2 –3 mol% Y2O3 ceramic and NiCrAlY powders. A fine-grained zirconia powder was chosen to lower the ceramic sintering temperature and achieve simultaneous metal and ceramic densification. Consolidation of FGM's was achieved by a short time field-assisted sintering technique. Sintering was performed either at a constant temperature or in a temperature gradient by using punches made of different materials (i.e., one graphite and one tungsten). A temperature gradient of at least 100 °C was required with a low value of 1200 °C at the metal end and exceeding 1300 °C at the ceramic end. Increasing the number of intermediate layers alleviates some of the cracks formed during sintering due to different coefficients of thermal expansion.

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Mourlas, Athanasios, Pandora Psyllaki, Dimitrios Chaliampalias, George Vourlias, Lyliana Kolaklieva, and Roumen Kakanakov. "Tribological Behaviour of Gradient TiAlSiN Superhard Coatings." Key Engineering Materials 674 (January 2016): 207–12. http://dx.doi.org/10.4028/www.scientific.net/kem.674.207.

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The present study addresses the influence of the gradient microstructure of nanocrystalline TiAlSiN coatings on their tribological behaviour. Cathodic arc deposition was applied to elaborate such coatings, with a total thickness of 3.5 μm, onto stainless steel substrates. Their microstructure has been characterised via Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS) and has been reported in detail previously. Since the main application of TiN-based coatings is the enhancement of the anti-wear resistance of metallic substrates, this work is focused on the tribological performance of gradient TiAlSiN coatings under dry sliding conditions. For this purpose, tests were carried out in a ball-on-disc apparatus, using an alumina ball as counterbody. The influence of the sliding velocity on the evolution of the friction coefficient and the wear lifetime of the gradient coatings has been evaluated in comparison to those of TiN coatings of the same thickness, tested under the same experimental conditions. It was found that the gradient microstructure results in an increase of the coatings’ mean lifetime by an average factor of three.

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Pedraza, F. "Implications of Diffusion on the Composition and Microstructures of Platinum Modified Aluminide Coatings on CMSX-4 Single Crystal Superalloy." Defect and Diffusion Forum 289-292 (April 2009): 277–84. http://dx.doi.org/10.4028/www.scientific.net/ddf.289-292.277.

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State-of-the-art aluminide coatings for high pressure aeroturbines rely on their chemical stability through the addition of platinum. In this work, the influence of diffusion on the composition and microstructure of Pt/Al coatings is investigated upon the different processing steps. Upon heat treatment of the electrodeposited Pt layers, the ready solubility of Pt in the ’-Ni3Al and its concentration gradient allow fast ingress of this element in the coating in spite of the higher diffusion coefficients of the substrate elements. The relatively high Pt contents at the surface thereafter promote Al ingress upon aluminisation by creating a greater concentration gradient between the coating atmosphere and the coating. This results in a -NiAl based coating grown by both Ni outward and Al inward diffusion. The diffusivity of Pt, Ni and Al being dependant on the stoichiometry of the -NiAl coating, different metal particles may precipitate mainly at the NiAl grain boundaries. In addition, the diffusion of the refractory elements towards the interdiffusion layer seems to be hurdled by increasing the Pt content. As a result of the countercurrent diffusion of species, different microstructures and compositions will appear across the coatings.

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Gerashchenkov, Dmitry A., A. M. Makarov, Ruslan Y. Bystrov, et al. "Technological Aspects of Obtaining Functional Gradient Coatings to Protect Machinery from Wear." Key Engineering Materials 822 (September 2019): 768–73. http://dx.doi.org/10.4028/www.scientific.net/kem.822.768.

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The article presents the results of research on the development of technology for the production of functional-gradient coatings with high levels of adhesive strength and hardness, as well as with low porosity. The coating was successfully tested and recommended to protect the elements and components of precision engineering.

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Song, Shu Xiang, Wei Zhi Yao, Zhang Jian Zhou, Wei Wei Cong, Yao Ma, and Chang Chun Ge. "Fabrication and Evaluation of Plasma-Sprayed Functionally Gradient W/Cu Coatings as Plasma Facing Materials in Fusion Devices." Key Engineering Materials 373-374 (March 2008): 31–34. http://dx.doi.org/10.4028/www.scientific.net/kem.373-374.31.

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Tungsten has been decided as the plasma facing material (PFM) for some high heat flux regions of the divertor in the International Thermo-Nuclear Experimental Reactors (ITER). In this paper, our efforts concentrated on the functionally gradient W/Cu coating fabricated on the oxygen free copper by atmosphere plasma spraying under the inert gases protection. The functionally gradient W/Cu coatings were designed to relieve the thermal stress during the spraying processes. For comparison, the tungsten coatings were also deposited directly onto the copper substrates by the same technology. XRD, SEM and EDS were applied to identify the phases, morphologies and compositions of these coatings. Tensile tests were performed to measure the bonding strength between the coatings and the substrates. Furthermore, water quenching and high heat loading experiments using a pulse laser beam were also carried out to estimate the thermal shock properties of these coatings.

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Dang, Bo, Tian Tian, Kai Yang, et al. "Wear and Deformation Performance of W/Ta Multilayer Coatings on Pure Cu Prepared by Double Glow Plasma Alloying Technique." Coatings 10, no. 10 (2020): 926. http://dx.doi.org/10.3390/coatings10100926.

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In this study, a multilayered hard coating with a tungsten matrix and a transition layer was deposited on pure copper by double glow plasma surface alloying technology, which aimed to provide the coating superior binding force and favorable matching of mechanical properties. The micro-hardness tester was adopted to measure the surface and cross-sectional hardness of the coatings. The nanoindentation test was used to measure the elasticity modulus of the coatings. Sliding wear tests under different conditions were performed on the W/Ta multilayer coating as well as the Cu substrate and W coating. The fairly low specific wear rate of the multilayer coating proved its excellent wear-resisting property, and the wear mechanism of the multilayer coating was mainly abrasive wear. In addition, a scratch test was executed to evaluate the deformation mechanism of the coating. Compared to the W coating, the persistence of the changing elastic–plastic deformation in the W/Ta multilayer coating improved the adhesion and resistance to plastic deformation. Moreover, the changing elastic–plastic deformation region is a benefit to the wear process, and the mechanical properties of the transition layer present a linear gradient descent instead of a vertical gradient, which makes a significant contribution in the wear stage. Further, the exploration of deformation mechanisms has a significant contribution to the design for multilayered hard coatings.

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Journal articles on the topic 'Gradient coatings'

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