Effect of ZrB2 on microstructure and wear properties of TC4 alloy coatings by laser direct energy deposition

Abstract

In this paper, ZrB₂/TC4 alloy coatings with different contents of ZrB₂ were prepared on the surface of TC4 titanium alloy using laser direct energy deposition technology. The effects of ZrB₂ content on the microstructure, phase, microhardness and friction and wear behaviors of the TC4 coating were investigated, and the enhancement mechanism of ZrB₂ on the coating properties was analyzed. The results show that with the increase of ZrB₂ content, the coating successively produces the white ring-like structure of the first and the last, the parallel structure of the fishbone and the staggered structure of the TiB compounds, and the microstructure of the coating is transformed from the elongated grains to the fine grains. The microhardness and wear rate of the 15 wt% ZrB₂/TC4 coating reached up to 352.1HV and 5.9 × 10−⁶ g/N•m, respectively. Compared with the 100%TC4 coating, the microhardness is increased by 14.6 % and the wear rate is decreased by 52.0 %, indicating that the addition of ZrB₂ was beneficial to improve the friction and wear properties of coating. Interestingly, when the content of ZrB₂ reached 20 %, the brittleness of the coating was too high, leading to the phenomenon of grooves on the wear surface of the coating, and the wear rate was reduced by only 45.5 %.