Comparison on multi-angle erosion behavior and mechanism of Cr3C2-NiCr coatings sprayed by SPS and HVOF

Abstract

Thermally sprayed cermet coatings are widely used to improve the wear resistance of component surfaces. In this study, Cr3C2-NiCr cermet coatings were deposited by shroud plasma spraying (SPS) and high velocity oxygen-fuel (HVOF) spraying. The erosion test of both coatings was carried out with simulating the environment of multi-angle high-speed erosion of small particles of turbine blades. Then, the microstructure, phase composition, microhardness and erosion wear behavior of both coatings were analyzed. The results showed that the HVOF coating was denser with fewer defects than the SPS coating. The microhardness of the HVOF coating was about 9% higher than that of the SPS coating, and the HVOF coating had better erosion resistance. The erosion rate of both coatings increased rapidly first and then decreased slowly with the increase of impact angle. It was noted that the erosion rate of the SPS coating and HVOF coating reached the maximum at the impact angle of 60° and 75°, respectively. For both coatings, at low impact angles, the erosion wear was dominated by micro-cutting, while it was gradually transformed to fatigue fracture spalling as the increasing impact angle. Specifically, large cracks in the carbide-rich region and extensive fatigue fracture spalling of the SPS coating could be observed at 60° impact angle, while the HVOF coating exhibited micro-cracks and the most severe sporadic spalling of chromium carbide particles at 75° impact angle.