Microstructure and Dry-Sliding Wear Behavior of Thermal Sprayed and Fused Ni-Based Coatings with the Addition of La_2O_3

摘要

A Ni-based alloy with 1.5 wt% of La_2O_3 powders was thermal sprayed onto steel substrate. The microstructure and dry sliding wear behavior of the coatings were studied by XRD, field emission gun scanning electron microscope (FEGSEM) and SEM analyses. The microstructure of the coating with 1.5 wt% of La_2O_3 differs widely from the coating without La_2O_3; the typical microstructure with 1.5 wt% of La_2O_3 is composed of net-like dendrite (Cr, Fe)_(23)C_6 and Cr_7C_3, cellular-dendrite Fe_(23)(C, B)_6, γ-Ni + Ni)5Si_2 interdendritic lamellar eutectic. Interestingly, significant amounts of net-like (Cr, Fe)_(23)C_6 and Cr_7C_3 hard phases as a wear-resistant skeleton were formed and uniformly dispersed in the coating. Meanwhile, blocky and rod-like hard-phase CrB scattered in the coating can also contribute to improving the wear resistance. The novel microstructure, therefore, is beneficial for wear resistance. Friction and wear tests without lubricant show that the friction coefficients of the coating are less than 0.57. There is an approximately linear relationship between friction coefficients and sliding speed. The wear rate slightly increases with an increase of load, and the wear rate of the coating slightly decreases with sliding speed.