Comparative studies on microstructure and properties of CoCrFeMnNi high entropy alloy coatings fabricated by high-speed laser cladding and normal laser cladding

Abstract

Two kinds of CoCrFeMnNi high entropy alloy (HEA) coatings were prepared by high-speed laser cladding (HS-) and normal laser cladding (N-), respectively. The phase, microstructure, micromechanical properties, and corrosion resistance of both coatings were analyzed. According to the results, both coatings are stable single-phase FCC structures with the dendrites microstructure. However, the dendrites of the HS-CoCrFeMnNi coating are finer. Owing to the low heat input and the quick cooling and heating characteristics of high-speed laser cladding, the width of the heat affected zone and the dilution ratio of the HS-CoCrFeMnNi coating are reduced. In addition, the microhardness of the HS-CoCrFeMnNi coating (∼ 184 HV0.2) is higher than that of the N-CoCrFeMnNi coating (∼ 160 HV0.2). The elastic modulus (Er) of the HS-CoCrFeMnNi coating is significantly increased in order to enhance its resistance to plastic deformation. The plastic storage energy Qp of the HS-CoCrFeMnNi coating is higher, revealing the improved crack resistance. The self-corrosion potential Ecorr of the HS-CoCrFeMnNi coating positively shifted by 0.142 V compared with the N-CoCrFeMnNi coating, and the self-corrosion current density Icorr decreased from 6.3 × 10−6 A/cm2 to 2.9 × 10−7 A/cm2 in 3.5% NaCl solution. Therefore, the HS-CoCrFeMnNi coating possesses better corrosion resistance and comprehensive mechanical properties.