Structure and high temperature wear characteristics of CVD coating on HEA-bonded cermet. Issue 15 (15th October 2019) - Chai, Binbin
Abstract: Ti(C, N)-based cermets with a CoCrFeMnNi high-entropy alloy (HEA) binder phase were coated via chemical vapor deposition (CVD). The influence of the HEA-bonded cermet substrate on the microstructure, orientation, adhesion, and high temperature frictional wear performance of the CVD coating was investigated. The results indicate that the HEA binder phase inhibits the growth of cermet grains and provides more nucleation sites for the coating. Thus, the coating on the HEA-bonded cermet has a smaller grain size. The substitution of HEA for the Ni binder phase increases the entropy value of the cermet system, resulting in a decrease in free energy. In the early stage of CVD, the gas atoms adsorbed on the solid surface with low free energy are in a more stable thermodynamic state, which enhances the adhesion strength between the coating and substrate. During high temperature frictional wear, the friction coefficient of the coating on Ni-bonded cermet is less than that of the coating on HEA-bonded cermet because of iron oxide lubricating films. However, the wear rate exhibits a reverse trend. The coating on the HEA-bonded cermet has the best wear resistance due to small grain size, superior hardness and excellent adhesion strength. The wear forms present in the CVD coatings are abrasive wear, adhesive wear and oxidation wear.