Tribological behaviors of high-hardness Co-based amorphous coatings fabricated by laser cladding.

Co-based metallic glasses with ultrahigh strength and high microhardness are regarded as ideal surface-coating materials to significantly improve hardness and wear resistance of substrate materials. In this paper, a Co-based amorphous powder with high glass-forming ability was prepared by gas-atomization technique. Then a large-area Co-based amorphous coating was fabricated from the powder by laser cladding technology. The effects of different laser parameters (i.e., laser scanning speed and operating voltage) on glass formation of the amorphous coating were investigated. Furthermore, the thermal properties, microhardness and wear resistance of the amorphous coating produced with an optimal laser parameter were evaluated. The results indicate that the Co-based amorphous cladding layer exhibits extremely high microhardness of ~14.9 GPa, which can significantly improve the wear resistance of the substrate. A complex wear-failure mechanism of the Co-based coating is clarified as a mixture role of abrasive- & fatigue-wear, oxidation wear and adhesive wear proofed by microstructural and element-distribution analysis of various worn surface. • Co-based amorphous coatings were fabricated with optimal laser-cladding parameters. • The coating shows high microhardness of ~15 GPa, 10 times higher than steel matrix. • The coating exhibits excellent wear resistance, ~20 times higher than the matrix. [ABSTRACT FROM AUTHOR]