Al–Cu-based in-situ reinforced gradient coating on aluminum alloy by laser cladding: Tribological behavior under gradient loading and thermal conditions

Abstract

The improvement of wear resistance has a profound effect on the far-ranging application of aluminum alloy. In this study, the Al–Cu-based in-situ reinforced composite coating was successfully manufactured on the AlSi10Mg substrate by laser cladding. The microstructure, microhardness and wear resistance under gradient loading (3 N, 6 N, 9 N, 12 N and 15 N) and thermal conditions (200 °C, 300 °C and 400 °C) of the composite coating were studied. The research results showed that the composite coating exhibited a gradient distributed microstructure due to the different diffusion degrees of Cu and Al atoms. The composite coating was mainly composed of Al4Cu9, Al7Cu4Ni and α-Al in the bottom, center and top area, respectively, and Al2Cu evenly distributed in each area. The microhardness showed gradient distribution owing to the gradient microstructure. Compared with the AlSi10Mg substrate, the composite coating possessed higher microhardness and better wear resistance contributed by the gradient Al–Cu intermetallic compounds. At room temperature, the main wear mechanisms of the composite coating changed from abrasive wear to adhesive wear with the increase of loading condition. At high temperatures, the main wear mechanisms of the composite coating were adhesive wear and plastic flow. During the wear process, Al–Cu intermetallic compound was the key to improving the wear resistance and stabilizing the friction coefficient.