Microstructural evolution and high-temperature oxidation resistance of NiCoCrAlYSiHf coatings after surface thermal modification with millisecond laser

Abstract

NiCoCrAlYSiHf coatings prepared by arc ion plating was thermally modified via millisecond laser technique. The microstructural evolution and oxidation resistance of the coatings before and after laser thermal modification were compared. Laser thermal modification significantly reduces the surface roughness of the coating, modifies the microstructure (introduction of dislocations, nano-particle precipitation), regulates the elemental distribution (Y-Al oxides), and forms ultrafine-grained particles on the surface. The experimental results show that these evolutions provide conditions for the improvement of the oxidation resistance of the coatings. In particular, Y-Al oxides can play an effective pinning role during long-term oxidation. And the ultrafine-grained particles formed on the surface promote the formation of Al2O3 oxide scale. Therefore, laser thermal modification can be an effective processing method to extend the service life of NiCoCrAlYSiHf coatings.