Effect of aluminizing coating on fatigue properties of DD6 single crystal superalloy

Abstract

To investigate the effects of aluminizing coating on the surface integrity and rotational bending high cycle fatigue performance of DD6 alloy， the chemical vapor deposition method is used to aluminize DD6 fatigue samples after standard heat treatment. The cross-sectional microstructure and elemental distribution of DD6 alloy samples with aluminizing coating are analyzed using SEM and EDS， and the high cycle fatigue properties of the uncoated and coated samples are tested at 760 ℃ and 980 ℃， respectively. The results show that the surface area of the sample with aluminizing coating is mainly divided into two layers： inner and outer. The outer layer is mainly composed of the β-NiAl phase， and the inner layer is a diffusion layer， containing many solid solution strengthening elements. The aluminizing coating can slightly reduce the rotational bending high cycle fatigue performance of the alloy at 760 ℃ and 980 ℃ and has a significant impact on the fatigue life in the high-stress amplitude region and a small impact on the low-stress amplitude region. The coupling effect of surface roughness， oxidation damage， and element interdiffusion is the fundamental reason for the difference in fatigue life between uncoated and coated samples.

Keywords

• dd6
• aluminizing coating
• fatigue
• single crystal superalloy