The Creep Crack Growth Behavior of GH3535 Superalloy at 650°C

Abstract GH3535 alloy is a kind of Ni-Mo-Cr based structural material independently developed by China especially for thorium molten salt reactor (TMSR) that is the only liquid fueled reactor among the six fourth-generation advanced fission reactors. GH3535 alloy has good high temperature mechanical properties and the purpose of this work is to evaluate the creep crack growth (CCG) performance of it. The CCG tests on GH3535 alloy were conducted with the compact tension (CT) specimen under different effective stress intensity factors Kn at 650°C. Based on this, the relationship between creep crack initiation time ti, creep crack growth rate da/dt and fracture parameter C* were obtained and compared with the result predicted by Nikbin-Simth-Webster (NSW) model. The microstructural degradation at creep rupture was characterized using scanning electron microscopy (SEM). The results show that in the double logarithmic coordinate system, the fracture parameter C* has a linear relationship with the crack growth rate da/dt and the crack initiation time ti which show C* can correlate well with the crack growth rate and crack initiation time. The NSW model under plane stress can better predict creep crack growth behavior. The crack propagates in two ways: firstly, it propagates along the grain boundary, and then enters the rapid propagation stage, where the ductile dimple fracture occurs.