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Due to wear and improper operation, many machine parts become useless, which is why issues of friction and wear remain constantly relevant across all industrial sectors. This paper presents the results of research on the microstructure and properties of a nanostructural composite coating containing solid lubricant. The coating was deposited from a mixture of nanostructural WC-12Co powder and nanostructural Fe3O4 powder using HVOF spraying. Despite significant differences in grain size and density of both powders, the deposited coating consisted of WC-12Co matrix containing evenly distributed Fe3O4. The XRD analysis of the coating confirmed the presence of both components and the presence of W2C, which resulted from the decarburization of WC due to the high temperature during the spraying process. Furthermore, the microstructure analysis of the coatings confirmed that they contained both nanostructural WC and Fe3O4 grains that were present in the feedstock. The coefficients of friction, microhardness, and wear of the nanostructured composite coatings were determined using an experimental binomial program. Based on the ANOVA conducted, it was determined that the most significant impact on the friction coefficient is the Fe3O4 content in the sprayed mixture, while the oxygen to propane ratio affects the microhardness. For the wear of nanostructural composite coatings, the most important parameter is the spraying distance. [ABSTRACT FROM AUTHOR]

This work presents the effect of surface roughness (Al 7075) on the microstructure and mechanical properties of cold-sprayed nickel coatings. Coating analysis included substrate surfaces and coating geometry, microstructure characterization, microhardness, nanohardness, elastic modulus, and adhesion. The results show that the surface preparation had a significant effect on coating adhesion and microstructure. The coating deposited at the highest gas temperature revealed a dense microstructure, showing very good adhesion of the impacting powder particles to the substrate and good bonding between deposited layers. The Ni grains with different shapes (elongated, equiaxed) and sizes of a few dozen to several hundred nanometres were present in the splats. An increase in temperature caused significant growth in coating thickness as a result of the powder grains' higher velocity. Moreover, higher gas temperature resulted in the enhancement of micro- and nanohardness, elastic modulus, and adhesion. The adhesive bond strength of Ni coatings in the tested temperature ranges from 500 °C to 800 °C increased with the increase in the surface roughness of the substrate. For the Al 7075 coarse grit-blasted (CG) substrate with the highest roughness, the adhesion reached the highest value of 44.6 MPa when the working gas was at a temperature of 800 °C. There were no distinct dependencies of surface roughness and thickness on the mechanical properties of the cold-sprayed nickel coating. [ABSTRACT FROM AUTHOR]

This paper presents a study on the effect of laser surface treatment on the microstructure and mechanical characteristics of cold sprayed Cr 3 C 2 -25(Ni20Cr)-(Ni-graphite) cermet coatings. The as-sprayed deposits retained the initial powder phase composition. The Cr 3 C 2 particles were homogeneously distributed within the deformed nickel-chromium matrix phase. Moreover, the carbide particles were heavily fragmented due to a high-velocity impact on the substrate or particles already embedded. The solid lubricant (graphite) was mostly distributed between crushed Cr 3 C 2 particles or deformed nickel-chromium matrix. The surface of the as-deposited coatings was laser-treated using a CO 2 laser. With the higher applied power of the laser beam, the changes in the coating microstructure and surface topography were more significant. The refinement of the deposit structure and formation of new phases such as Cr 7 C 3 and Cr 2 O 3 were observed. All coatings, both those cold sprayed and those laser-treated, revealed compressive residual stresses, which increased with higher laser power. The post-deposition laser modification of the coating surfaces improved their mechanical properties by almost half. • The laser modification led to refinement of (Cr 3 C 2 –25(Ni20Cr))-(Ni-graphite) coatings structure. • The cold sprayed and laser-treated cermet coatings revealed compressive residual stresses. • The laser surface modification improved the mechanical properties of coatings by almost half. [ABSTRACT FROM AUTHOR]