Slurry erosion behaviour and mechanism of HVOF sprayed micro-nano structured WC-CoCr coatings in NaCl medium

In this work, we fabricate nanostructured, bimodal, and multimodal WC-10Co4Cr coatings via two high velocity oxy-fuel (HVOF) systems and investigate the coatings' microstructure, mechanical, electrochemical properties and slurry erosion resistance in 3.5 wt% NaCl solution. The multimodal coating, with a dense microstructure, exhibits lowest decarburization and highest resistance to both corrosion and slurry erosion. The slurry erosion resistance of multimodal coating is enhanced approximately 18% and 11% than the nanostructured and bimodal coatings. However, the performance can easily drop to the worst by changing the HVOF spraying method. The outstanding performance can be attributed to uniform distribution of the multiscale WC grains in the multimodal coating, which effectively reduces the material loss rate during corrosion-accelerated erosion in NaCl solution.