Microstructural evolution of thermally grown oxide of an arc ion plated MCrAlX coatings after high-current pulsed electron beam treatment

Abstract

An arc ion-plated NiCoCrAlYHfSi coating modified by a high-current pulsed electron beam (HCPEB) was examined in this study. The dynamic growth behavior and formation mechanisms of the thermally grown oxide (TGO) of the original and modified coatings were thoroughly compared by isothermal oxidation at 1050 °C. HCPEB irradiation led to the transformation of the rough original coating into a flat, smooth, and dense structure. Furthermore, Y-Al nanoparticles and high density of dislocations were also obtained in the modified layer. These modification characteristics can establish favorable conditions for the rapid accumulation and stable growth of the protective Al2O3 particles. With the extension of oxidation time, the CrO3 formed in the oxide film left many small pits after volatilization, but these pits were filled with Al2O3 particles. Compared with the oxide film of the original coating, the TGO of the modified coating is flat, continuous, and dense, and its growth rate is notably slower. Also, the growth of Ni, Cr, and Co rich oxides was expectantly restrained. Obviously, the HCEPB technique has the capacity to change the growth behavior of the TGO and significantly enhance the coating's resistance to high-temperature oxidation.