Microstructure and Crack Propagation Behavior of GH864 alloy

Abstract

Crack propagation rates after different heat treatments for GH864 alloy are measured under fatigue/creep interaction condition at 650℃ in air. The influence of heat treatment and microstructure are analyzed. The microstructure and crack propagation behavior of GH864 alloy are studied by means of microstructure analysis,fatigue crack growth and fracture morphology analysis. The crack propagation rates have a good description by Paris formula. The results indicate that the fatigue crack growth rates of alloys are decreased after these heat treatments;the grain sizes affect strongly on crack propagation rates and the coarse grain structure obviously reduces the fatigue crack growth;the precipitations of grain boundary is important to the crack propagation rate of GH864 alloy,but the size of γ prime phase strengthen particles has little effect on the fatigue crack growth. The microstructure morphology and fracture analysis can well explain the test results of crack propagation curves after different heat treatments. The fracture with fatigue striation character corresponds to the lower crack growth rates, while the intergranular fracture corresponds to higher rates.