Microstructure and wear resistance of compositionally graded Ti-Si laser-clad coatings

摘要

A Ti-Si 3-layer compositionally graded coating with a Si content ranging from 4 at.-% to 30 at.-% was fabricated on a commercial Ti-alloy substrate using laser cladding, with an aim of improving the wear resistance of the substrate. The composition was designed with a relatively soft layer close to the substrate, and a hard layer at the exterior surface. This was to overcome the cracking problem at the coating-substrate interface. Direct single layer cladding of the 30 at.-%Si alloy on the Ti-alloy resulted in the development of cracks at the interface, which grew deep into the coating itself. On the contrary, cracks were completely absent in the case of the graded coating. The hardness of the top layer of the coating was double that of the substrate; also the wear resistance of the coating, measured in terms of wear depth, was about four times higher than that of the substrate.