Effects of WC addition on the erosion behavior of high-velocity oxygen fuel sprayed AlCoCrFeNi high-entropy alloy coatings

In this study, AlCoCrFeNi (H1), AlCoCrFeNi+25 wt%WC-10Co (H2), and AlCoCrFeNi+50 wt%WC-10Co (H3) high-entropy alloy (HEA)/tungsten carbide (WC) composite coatings were deposited onto 316 stainless steel substrates by applying the high-velocity oxygen fuel spraying technology. The phase, layered microstructure, microhardness, and erosion behavior of the coatings were analyzed by performing X-ray diffractometry, scanning electron microscope/energy dispersive spectrometry, Vickers microhardness testing, and slurry erosion testing. The effects of WC addition on the erosion behavior and mechanism of the coatings at different flow velocities were investigated. The deposited coatings were compacted and adhered well to the substrate. The AlCoCrFeNi coating was composed of BCC and FCC phases. The porosity of the H1, H2 and H3 coatings were 0.24%, 0.33% and 0.45%, respectively, and were less than 1%. The microhardness of the HEA/WC composite coatings was positively correlated with WC content. The volume loss and rate of volume loss of the coatings decreased with the addition of WC. The erosion mechanism of the AlCoCrFeNi coating was typical ductile wear, with a small amount of interlayer peeling. Furrows, cuttings, and plastic deformation caused by low grazing angles contributed to the failure of the AlCoCrFeNi coating. In the HEA/WC composite coatings, WC protected the HEA from more severe plastic deformation by second-phase strengthening, and the main erosion mechanism of WC was gradual brittle detachment caused by high-grazing-angle erosion in which craters, cracks, and massive spalling were responsible for the erosion process.