Study on the effect mechanism of aluminizing on fatigue performance of K403 nickel-based superalloy

Aluminizing is widely used in the surface protection of high-temperature components in the aeroengines, but the effect mechanism of aluminizing on the fatigue properties of matrix alloys is unclear. Based on the analysis of microstructure and element distribution in an aluminized layer of K403 nickel-based superalloy, the effect of the thickness of the aluminized layer on the fatigue life is investigated in this study. By analyzing the phase composition on the surface of the aluminized layer with different thicknesses and combined with first-principles calculations, the effect mechanism of the surface phase structure on the fatigue performance of aluminized alloys is proposed. Results show that the aluminized layer presents an obvious layered structure along the depth direction, and the aluminum content gradually decreases from the outside to the inside. The fatigue life of the aluminized samples is the highest when the surface of the aluminized layer is of the NiAl phase, with the strongest metallic bond characteristics. However, when the surface is of the Ni2Al3 phase with high hardness and brittleness, the fatigue life is the lowest.