Effect of Ti content on the microstructure and mechanical properties of laser clad Ti/B4C/dr40-based composite coatings on shaft parts surface

Abstract

As a transmission part, the service life of the shaft parts directly affects the machining efficiency and economic benefit, and requires higher surface hardness and wear resistance. In this study, the Ti/B4C/dr40 composite powder was cladded on the shaft part surface via laser cladding to improve the microhardness and wear resistance. The microstructure evolution and phase structure were analyzed to reveal the strengthening mechanism of Ti and B4C on dr40 coating. The Ti/B4C/dr40 composite coating with low defects and good interface metallurgical bonding quality between coating and substrate was prepared on the 45# steel shaft part. The results show that the main phase in the Ti/B4C/dr40 composite coating is TiC, TiB2, Cr2C3, (Ti, Cr) C, (Ti, Cr, Fe, Ni) (C, B). With the addition content of Ti increasing, the grain densifies, the sieve-reticular structure and small strip phase at grain boundary and intergranular area change as massive phase. Moreover, the microhardness improves up to 2.05 times than that of dr40 coating. The in-situ synthesis of carbides and borides are evenly distributed in the coating, which improves the deformation resistance of the coating. In addition, the precipitation and solid solution strengthening caused by reinforcement phase also enhanced matrix strength for supporting reinforcement phases, improving the coating wear resistance.