Effect of Heat Treatment on Microstructures and Stress Rupture Properties of a Hot-Corrosion Resistant Single Crystal Superalloy

Abstract:

The effects of heat treatment on the microstructures and rupture properties at 1070 ℃/140 MPa of a hot-corrosion resistant single crystal superalloy was investigated. The results show that long-term homogenization heat treatment significantly reduces element segregation. With the extension of homogenization time, the area fraction of micropores gradually increases, the average size keeps increasing, and the density of micropores increases firstly and then decreases. With the increase of primary aging temperature, the size of γ" phase enlarge gradually, the area fraction of γ" phase frist increases and then decreases. The stress rupture life of the alloy increases first and then decreases with the increase of the primary aging temperature. When the primary aging temperature is 1100 ℃, the size of the cubic γ" phase is about 370 nm and the squareness is better, the area fraction of the γ" phase is the largest and the stress rupture life is the highest. The stress rupture fracture is characterized by ductile fracture. The carbides and micropores at the sub-grain boundary are the main crack sources that cause the stress rupture fracture of the sample.

Key words:hot-corrosion resistant single crystal superalloy; heat treatment; microstructure; stress rupture property