Effect of Grain Boundary Morphology on the High Temperature Tensile Properties of Developed Ni-Based Superalloy (LESS)

In order to investigate the mechanical properties of developed wrought γ'-hardened Ni-based superalloy, LESS alloy (Low Eta Sigma Superalloy), and understand deformation behavior, tensile tests were carried out from room temperature 800oC in comparison with IN 740H alloy. Like other superalloys, found be dependent on temperature. As rose between 700oC, ultimate strength (UTS) decreased slightly, then sharply. The yield (YS) was about 40% higher than that 700oC. On basis microstructure observations, high is thought result dense grain boundary, where fine carbides (MC, M23C6) γ' phase form a continuous film structure, which more effectively suppressed dislocation movements during deformation. It mode changed γ'- shearing mixed (γ'-shearing + climb) at around 700~800oC. Although main fracture ductile dimple fracture, elongation due local brittle region caused by micro-twins.