Oxidation resistance of Al-Si coating on K4104 superalloy at 1000°C

The surface morphology, cross - sectional microstructure and compositional change of Al-Si diffusion coatings oxidized in air at 1000°C for different time were studied by scanning electronic microscopy (SEM) equipped with energy dispersive analysis of X-ray(EDAX). The oxidation kinetics of the coating was monitored by intermittent weight gain measurement. It was revealed that the addition of Si in Al-Si coating accelerates the transformation from θ-Al₂O₃ to α-Al₂O₃ and is in favor of the formation of compact oxide scale. Meanwhile, it can promote the formation of carbide barrier layer, thereby, suppresses the elements diffusion between coating and substrate so that Al-Si coating is superior to Al coating.