Investigation on solid particles erosion resistance of laser cladded CoCrFeNiTi high entropy alloy coating

Abstract

High entropy alloy (HEA) as coating material has more economical application value. In this study, CoCrFeNiTi HEA coating without cracks and pores was successfully prepared on 304 stainless steel substrate by laser cladding. The phase structure of the CoCrFeNiTi HEA coating was composed of main phase with an FCC lattice, Fe and Cr rich phase with an SC lattice and CoTi2 type Laves phase. The microstructure of the prepared coating consisted of bonding zone and cladding zone. It was an obviously metallurgical bonding between the coating and substrate and typical columnar dendrites were generated with growth direction perpendicular to the interface in the bonding zone. The cladding zone showed a typical long strip proeutectic structure and a lamellar eutectic structure. The average microhardness of CoCrFeNiTi HEA coating reached to 568 HV0.2, which was approximately 2.5 times higher than that of the substrate (236 HV0.2). Erosion tests were conducted on both CoCrFeNiTi HEA coatings and the substrates with an erosion angle of 30 and 90°. The results showed that CoCrFeNiTi HEA coating exhibited much lower erosion rates with an erosion angle of 30° (0.68 mg/cm2) and 90° (0.42 mg/cm2). Ploughing and micro-cutting were the two primary erosion mechanisms of material loss for CoCrFeNiTi HEA coating at oblique erosion angles, while the erosion mechanism was replaced by the formation of craters at vertical erosion angles.