In this study, MCrAlY-Al 2 O 3 composite powders were produced by ball milling and deposited by plasma, HVOF, and cold spraying. The results show that Al 2 O 3 fractions can be well controlled using composite powder due to non-preferential impact debonding of the matrix and Al 2 O 3 . The microstructure of spray powders is well retained in HVOF and cold-sprayed coatings due to the unmelted or partially molten condition of the spray particles. In the case of plasma-sprayed coatings, however, most Al 2 O 3 particles segregate at lamellar interfaces, forming a continuous oxide scale on the splat. The cold-spray coatings exhibit the highest hardness due to the work hardening effect of kinetic deposition.

In this study, WC-CoWC coatings were produced by HVOF spraying using bimodal-structured WC-Co powder with both micro- and nano-sized WC particles. Due to the melting characteristics of the powder during spraying, the microsized particles are retained in the deposit, but the nanosized particles dissolve into the Co matrix, forming a Co-W-C ternary phase. Compared to coatings sprayed from conventional WC-CoWC powder, the bimodal coatings are more resistant to corrosion and wear and are comparable in microhardness.

In this study, carbide-based cermet (WC-Co, WC-NiCr, Cr 3 C 2 -NiCr) coatings were prepared by thermal spraying and efforts were made to explore the laser remelting effects on the coating microstructure, hardness, adhesion and tribological behavior under different conditions. Results obtained showed that under elected remelting parameters, laser-treated coatings exhibit denser structures and improved microhardness with smaller variability, as well as enhanced adhesion strength between coating and substrate arising from metallurgical element diffusion. In dry sling condition, HVOF sprayed WC-Co coating after laser remelting showed superior wear resistance, however, contrary to the lubricated condition, which may attribute to more lubricant stored in as-sprayed coatings with higher porosity. Solid particle erosion tests suggested that anti-erosion property of plasma sprayed Cr 3 C 2 -NiCr coating by laser remelting are increased, regardless of erosion velocity and angle. Additionally, the wear loss of laser-treated coating increased with erosion velocity, but due to its improved ductility shows no obvious relation to the erosion angle changing from 30 to 90 degree, which is accordance with the wear surface observation and tribological mechanism analysis.