Copper-coated graphite and copper mixture powders were deposited on AZ31B magnesium alloy and 6061 T6 aluminum alloy substrates under different process parameters by a solid-state cold spray technique. The microstructure of the copper-coated graphite and copper composite coatings was visually examined using photographs taken with an optical microscope and a scanning electron microscope. The surface roughness of the coatings was investigated with a 3D profilometer. The thickness of the coatings was determined through the analysis of the microstructure images, while the adhesion of the coatings was characterized using the scratch test method. The results indicate that the surface roughness of the coatings sprayed on the two different substrates gradually decreases as gas temperature and gas pressure increase. Additionally, the thickness and adhesion of the coatings deposited on the two different substrates both increase with an increase in gas temperature and gas pressure. Comparing the surface roughness, thickness, and adhesion of the coatings deposited on the two different substrates, the surface roughness and adhesion of the coatings on the soft substrate are greater than those of the coatings on the hard substrate, while the thickness of the coatings is not obviously affected by the hardness of the substrate. Furthermore, it is noteworthy that the surface roughness, thickness, and adhesion of the copper-coated graphite and copper composite coatings sprayed on the two different substrates exhibit a distinct linear relationship with particle velocity.

Sintering additives are commonly used to reduce the conditions required for densification in composite ceramics without compromising their performances simultaneously. Herein, SiC/SiC_w-Y₂O₃ composite ceramics with 10 vol.% SiC whiskers (SiC_w) and different Y₂O₃ contents (0, 2.5, 5, 7.5, and 10 vol.%) were fabricated by hot-pressed sintering at 1800 °C, and the effects of Y₂O₃ content on the microstructure, mechanical properties, and tribological behaviors were investigated. It was found that the increased Y₂O₃ content can promote the densification of SiC/SiC_w-Y₂O₃ composite ceramics, as evidenced by compact microstructure and increased relative density. The Vickers hardness, fracture toughness, and flexural strength also increased when Y₂O₃ content increased from 2.5 vol.% to 7.5 vol.%. However, excessive Y₂O₃ (10 vol.%) aggregated around SiC and SiC_w weakens its positive effect. Furthermore, the Y₂O₃ additive also reduces the coefficient of friction (COF) of SiC/SiC_w-Y₂O₃ composite ceramics, the higher the Y₂O₃ content, the lower the COF. The wear resistance of SiC/SiC_w-Y₂O₃ composite ceramics is strongly affected by their microstructure and mechanical properties, and as-sintered SiC ceramic with 7.5 vol.% Y₂O₃ (Y075) shows the optimal wear resistance. The relative density, Vickers hardness, fracture toughness, and flexural strength of Y075 are 97.0%, 21.6 GPa, 7.7 MPa · m^1/2, and 573.2 MPa, respectively, the specific wear rate of Y075 is 11.8% of that for its competitor with 2.5 vol.% Y₂O₃.