Gradient Coating of Laser Cladding TiB2/Ti-Based Alloy on Titanium Alloy Surface

The technology of the TiB2/TiB cladding layer addresses the issue of the insufficient wear resistance of cup-shaped parts composed of titanium alloy materials. In order to eliminate the cracking problem of laser cladding TiB2/Ti-based alloy, 30%TiB2/Ti-based alloy gradient coating was prepared on the surface of titanium alloy by laser cladding in this study. The results revealed that the microstructure of the matrix and the cladding layer is metallurgically bonded. The microstructures of the cladding layer appear as rod-like and coarse-grained features on the surface, and fine needle-like and small-grained morphologies inside. The fine needle-like TiB precipitated in situ from the melt has a flat interface with Ti and exhibits a low degree of interfacial mismatch, while the interface between small particle-like TiB and Ti is wavy and has a high degree of interfacial mismatch. The gradual increase in the amount of TiB is present from the surface to the bottom of the cladding layer, while the amount of unmelted TiB2 particles decreases. The chemical structure of the cladding layer is mainly presented as TiB2, TiB and α-Ti phases. The maximum hardness of the cladding layer is 725 HV0.2, where it is more than twice the hardness of the substrate. The fretting wear resistance of the cladding layer is better than that of the titanium alloy substrate under low loads (50 N–100 N), while a high load (more than 150 N) triggers a reverse outcome.