Effect of NiCr content on the solid particle erosion behavior of NiCr-Cr3C2 coatings deposited by atmospheric plasma spraying

Homogeneous coatings cannot meet the overall erosion-resistance requirements for an entire blade since materials present different erosion resistances at various impact angles. In this work, NiCr-Cr3C2 coatings with different NiCr contents were prepared on FV520B steels through atmospheric plasma spraying (APS) by using a double-channel powder feeder. The composition and microstructure of the as-sprayed coatings were examined by SEM, EDS, and XRD analyses, and microhardness was determined by microhardness tests. The erosion performance of NiCr-Cr3C2 coatings under different testing conditions (impact angle, solid particle size, solid particle velocity, and NiCr contents) were further evaluated with a gas solid two-phase testing machine. Furthermore, the erosion wear mechanism of NiCr-Cr3C2 coatings with different NiCr contents at various impact angles was investigated. The results showed that the phase distribution inside the NiCr-Cr3C2 coatings became uneven with the increased NiCr content, leading to the fluctuation of microhardness. The erosion rate of 25 wt% NiCr-Cr3C2 coating initially increased and then decreased with increasing impact angle and solid particle size. The erosion rate was also improved rapidly with the increased erosion velocity for all impact angles. It was found that at low impact angles, the erosion resistance of NiCr-Cr3C2 coatings was increased with higher ceramic content because of the micro-cutting failure. By contrast, at medium and high impact angles, the erosion resistance of the coating could be improved by increasing metal content since coatings are eroded through fatigue spalling and rigid fracture.