Friction and wear behaviors of Nb-Ti-Si-Cr based ultrahigh temperature alloy and its Zr-Y jointly modified silicide coatings

Zr-Y jointly modified silicide coatings were prepared on an Nb-Ti-Si-Cr based ultrahigh temperature alloy by pack cementation process. The wear behaviors of both the base alloy and coatings were comparatively studied at room temperature and 800 °C using SiC balls as the counterpart. The Zr-Y jointly modified silicide coating is mainly composed of a thick (Nb,X)Si2 outer layer and a thin (Ti, Nb)5Si4 inner layer. The coatings possess much higher microhardness than the base alloy. The wear rates of both the base alloy and coatings increase with increasing the sliding loads. However, the coatings have much lower wear rates than the base alloy under the same sliding conditions. The coatings have superior anti-friction property, and can provide effective protection for the base alloy at both room temperature and 800 °C in air.