Microstructure and properties of Cu-Cr-SiC in-situ composite coatings by laser cladding

Utilizing a laser cladding approach, three types of in-situ composite coatings (Cu-16Cr-4SiC, Cu-32Cr-8SiC, and Cu-48Cr-12SiC) were prepared on the CuCrZr alloy substrate. A biphasic structure as a result of the liquid-liquid phase separation (LLPS) were observed in the situ composite coatings, consisting of the Cr-rich phases (Cr3Si and Cr23C6) and the Cu-rich phase (Cu solid solution phase or κ-Cu7Si phase). The in-situ composite coating's "bilayer microhardness" properties are therefore visible, and the microhardness of the Cr-rich zone (1149–1326 HV0.5) is up to around ten times that of the Cu-rich zone (125–284 HV0.5). With the decreased of Cu content, the diffused Cr-rich phase in the cladding coating were transitioned to a laminar segregation. More interestingly, this microstructure characteristic is related to the laser cladding process parameters. The predominant wear mechanism of the coatings are hence delamination produced by matrix spalling along the friction surface. The wear rate of Cu-48Cr-12SiC coating is just 16.1 % of the substrate, with 6.9 % IACS conductivity.