Investigation of Tribology Performance of Laser-Cladding Titanium-Based Composite Coatings on TC4 (Ti-6Al-4V) Surface

Abstract

Titanium-based B₄C/Ni-graphite/Cu composite coatings through laser cladding, employing rare earth oxides to minimize coating defects were fabricated. Various laser powers have been compared based on the coatings' microhardness, friction coefficient, and mass wear rate to determine the optimal power setting. The mechanism underlying the enhanced coating properties was analyzed through microstructural and phase analysis, and the results indicate improvements in both hardness and wear resistance. Microscopic examination reveals that the coating's upper surface contains numerous unmelted B₄C particles, as well as reinforcing phases such as TiC, TiB, and Ti-containing metallic compounds, which contribute to hardness enhancement. The highest average hardness on the coating's upper surface, approximately 2.3 times that of the substrate, is achieved at 1200 W, reaching 872.62 HV0.5. In terms of wear resistance, nickel-encapsulated graphite was retained on the coating's surface, reducing the wear rate. Optimal friction coefficient (0.169, a 54.55% reduction compared to the substrate) and wear resistance (mass wear rate of 1.47%, a 19.89% reduction compared to the substrate) are observed at 600 W. Additionally, the coating's upper surface hardness at 600 W is 1.62 times that of the substrate. Overall, the coating at 600 W exhibits the best performance.