Dilution Induced Variation of Microstructure and Mechanical Properties on Co-Cr-Fe-Ni High Entropy Alloy Coatings Prepared by Laser Cladding

Abstract

The excellent performance of high entropy alloy (HEA) has attracted widespread attention to the preparation of HEA coatings. In this study, we prepared non-equiatomic Co-Cr-Fe-Ni HEA coatings using laser cladding method with Co-Cr-Fe-Ni cable-type welding wire (CTWW) as the filling material and investigated the effect of dilution rate on the microstructure evolution of coatings. By changing the wire feeding speed, a large dilution rate range was obtained which is from over 80% to below 20% and a variation of the coating’s microstructure and mechanical properties was discovered within this large dilution rate range. All of the coatings are dense and uniform, with good metallurgical bonding. When the dilution rate drops from above around 35%-40% to below, the coating transitions from face centered cubic (FCC) and body centered cubic (BCC) dual-phase to FCC single-phase, and the hardness instantly drops from about 425HV to below 175HV. The interlaced distribution and dislocation pile-up of the layered BCC eutectic structure within the FCC phase are the main reasons for this phenomenon. Therefore, controlling the dilution rate is an effective way to regulate the performance of Co-Cr-Fe-Ni HEA coatings.

Keywords: Laser cladding, Co-Cr-Fe-Ni HEAs, cable-type welding wire, Microstructure, dilution