Effects of shot peening on surface integrity and fatigue properties of DD412 single crystal superalloy

Abstract

To improve the fatigue performance of turbine blade tenon， the effect of shot peening on the surface integrity and high temperature fatigue performance of DD412 single crystal alloy was investigated. The surface morphology， roughness， hardness gradient and microstructure after shot peening were characterized by white light interferometer， roughness tester，microhardness tester， scanning electron microscope and transmission electron microscope respectively. The results show that after shot peening， the surface grinding tool marks are eliminated， and the surface micro stress concentration factor is significantly reduced. Severe plastic deformation occurr in the surface layer of the specimen， and a hardened layer with a depth of about 0.10-0.32 mm is formed.The mean fatigue life of the optimal shot peening specimens at 600 ℃/500 MPa is increased by more than 21.7 times， and the median fatigue limit at 600 ℃ is increased by 17.3%. The favorable change of surface integrity is the main reason for the improvement of high temperature fatigue properties of DD412 alloy after shot peening.

Keywords

• shot peening
• single crystal alloy
• surface integrity
• fatigue life
• microstructure
• hardness