Effects of Vanadium Addition on Microstructure and Tribological Performance of Bainite Hardfacing Coatings

New hardfacing coatings with different vanadium (V) additions were prepared by surfacing technology. The microstructures of the hardfacing coatings were analyzed by field emission scanning electron microscope equipped with energy dispersive X-ray spectrometry and examined by transmission electron microscope. The hardness and wear resistances of the hardfacing coatings were measured. Worn debris were collected at the end of wear test and analyzed. The precipitation temperature of the phases in the hardfacing coatings and the mass fraction of MC carbide were calculated by Jmatpro software. The experimental results show that, the hardfacing coating mainly consists of granular bainite. No significant change in the size of linear martensite-austenite (M-A) islands is observed with the increase of V addition, while the size of massive M-A islands is decreased. The wear resistance of the hardfacing coating reaches a maximum level with V content of 0.14 wt.%. The calculated results show that, the mass fraction of MC carbide is increased with the increase of V content. Based on calculation following two-dimensional mismatch theory, MC carbide is a heterogeneous nucleus of the ferrite resulting refined ferrite in the hardfacing coating.