Influence of Heat Treatment Temperature on the Microstructures and High Cycle Fatigue Properties of DD6 Single Crystal Superalloy

Abstract

The effect of heat treatment temperature on the microstructure and the high cycle fatigue property of DD6 single crystal superalloy was investigated. After standard heat treatment, the alloy was hold at 1200°C and 1300°C for 1h respectively, and then air-cooled. The results showed that after heat treatment at 1200°C for 1h, the size of γ′ particles became slightly larger and quite unevenly, at the same time, the serrated γ/γ′ interface appeared. After heat treatment at 1300°C for 1h, the small irregular γ′ particles re-precipitated. In addition, a small number of fine secondary γ′ particles were also observed in the matrix channel of the alloy after primary aging of 1200°C/1h and 1300°C/1h. The high cycle fatigue properties of the alloy by standard heat treatment were higher than that of the alloy by 1200°C/1h and 1300°C/1h, but the decreased degree of 1200°C/1h was much bigger than that of 1300°C/1h. Analysis on fracture surfaces of the alloy at 800°C demonstrated a quasi-cleavage mode.

Effect of Heat Treatment on Microstructure Evolution in DD9 Single Crystal Turbine Blade

“…A low-cost DD9 nickel-based single crystal superalloy with excellent properties and good castability has been developed for aero-engine turbine blades [4][5][6][7][8][9]. The properties of single crystal turbine blades alloy mainly depend on the microstructure, which especially affect the creep rupture properties and fatigue properties at high temperatures [10][11][12][13][14][15][16][17][18]. Because of the differences of the section dimensions from the tip to the tenon of a turbine blade, there are obvious different cooling rates in different sectional positions of a turbine blade during directional solidification process.…”