Microstructures and Physical Properties of CoCrFeNiMoxSi0.3 High-entropy Alloy (HEA) Coatings Laser Clad onto Q235 Steel

CoCrFeNiMoxSi0.3 (x=0.5, 1.0, 1.2 and 1.5) high-entropy alloy (HEA) coatings were prepared by laser cladding with a CO2 laser on the surface of Q235 steel. Thereafter, the microstructures and physical properties were investigated. The laser clad CoCrFeNiMoxSi0.3 coatings consisted of face-centred cubic (FCC) phase, a few body-cantered cubic (BCC) phases and second phase Fe3Mo. Typical cellular dendrites with strip-shaped second phases were generated in CoCrFeNiMo0.5Si0.3 coating. Lamellar-like structures arranged inside the grains and feather-like structures accompanied with granular second phases were formed in the laser clad CoCrFeNiMo1.0Si0.3 coating. For the CoCrFeNiMo1.2Si0.3 coating, colum-nar crystals were formed with many fine precipitations between BCC phases. In the CoCrFeNiMo1.5Si0.3 laser clad coating, parallel Widma-nstatten side-plates and some short side-plates with granular second phase were generated. Microhardness and wear resistance of the laser clad coatings were elevated with the increase of Mo element due to solid solution strengthening and second phase strengthening. Additionally, fatigue spallations were distinguished on the surfaces of the CoCrFeNiMo0.5Si0.3 and CoCrFeNiMo1.2Si0.3 laser clad coatings. Shal-low scratches and local spalling pits were found on the wear surface of CoCrFeNiMo1.0Si0.3 laser clad coating.