Effects of Annealing on the Microstructures and Wear Resistance of CoCrFeNiMn High-Entropy Alloy Coatings

CoCrFeNiMn high-entropy alloy (HEA) has great potential for industrial application due to its excellent mechanical properties and remarkable fracture toughness. In this study, CoCrFeNiMn HEA coatings (HEACs) were deposited on 316L stainless steel by detonation spraying technique, and annealed at two different temperatures. Phase structures, microhardness, and wear resistance of the as-sprayed and annealed HEACs were systematically investigated. It was found that both as-sprayed and annealed coatings were in a face-centered cubic solid solution structure, and contained a small amount of oxides, which would be easy to precipitate at the high annealing temperature. The microhardness of as-sprayed HEACs showed a high average value of ~520 HV, which increased to ~551 HV after annealing at 600 °C. And it decreased significantly to ~307 HV at annealing temperature of 900 °C as a result of grain growth. The wear tests demonstrated that the HEACs annealed at 900 °C had excellent wear resistance, while the as-sprayed HEACs had a high volumetric wear rate as compared with the annealed ones, which is ascribed to the improvement of cohesive strength of the splats by annealing: a strong metallurgical bonding between the splats was formed, and the splats of the annealed coatings were more difficult to peel off.