Effects of laser remelting on microstructure and tribological properties of plasma–sprayed Fe45Mn35Co10Cr10 high–entropy alloy coating

Abstract

To further improve the Fe45Mn35Co10Cr10 high–entropy alloy coating prepared by plasma spraying, laser remelting was used to improve its structures and tribological properties. The effects of laser remelting on the microstructure, element composition, phase and hardness of obtained coating were investigated using a super depth of field microscope, energy dispersive spectrometer, X–ray diffraction and hardness tester, respectively. The tribological properties were measured via a ball–on–disk tester at room temperature and 500 °C, and the wear mechanisms were also discussed. The results show that the laser–remelted HEA coating is still composed of face–centered cubic structure, and its hardness is increased by ~301.4% compared with the plasma–sprayed coating, which is attributed to the grain refinement and solid solution strengthening effects. The average coefficient of friction and wear rate of laser–remelted HEA coating is superior to the plasma–sprayed HEA coating, showing that the laser remelting process plays the roles of friction reduction and wear resistance. The wear mechanism of plasma–sprayed HEA coating at room temperature is fatigue wear, abrasive wear and oxidative wear; while that of laser–remelted coating is abrasive wear and oxidative wear. Moreover, the wear mechanism of plasma–sprayed coating at 500 °C is adhesive wear, abrasive wear and oxidative wear, while that of laser–remelted HEA coating is adhesive wear and oxidative wear, which is attributed to the reduction of plastic deformation by the softening effect at high temperature.