TGO and Al diffusion behavior of CuAlxNiCrFe high-entropy alloys fabricated by high-speed laser cladding for TBC bond coats

CuAlxNiCrFe (x = 0.5, 1, 1.5, 2) high-entropy alloys (HEAs) with good high-temperature oxidation resistance were deposited as bond coats via high-speed laser cladding. The microstructure of the CuAlxNiCrFe bond coats exhibited the columnar-to-equiaxed grain transition with increasing Al content. All bond coats generated a uniform and dense aluminum oxide layer and exhibited a low thermally grown oxide (TGO) growth rate after 100 h of oxidation at 1100 °C. During oxidation, CuAl1.5NiCrFe exhibited an extremely low Al diffusion coefficient, and the grain size of CuAlNiCrFe only grew by ~20%. [Display omitted] ●More Al makes the microstructure and grain of CuAlxNiCrFe from columnar to equiaxed.●CuAlxNiCrFe bond coats only generate dense α-Al2O3 as TGO layer.●The diffusion coefficient of Al in CuAl1.5NiCrFe at 1100 ℃ is as low as 1.43 * 10−16 m2/s.●Grain size of CuAlNiCrFe grow from 4.43 µm to 5.33 µm after 100 h oxidation at 1100 ℃.●CuAlxNiCrFe exhibits small volume shrinkage and high oxidation activation energy.