HEAT TREATMENT EFFECTS ON CREEP BEHAVIOR OF DIRECTIONALLY SOLIDIFIED CM247LC SUPERALLOY

摘要

This study investigates how the heat treatments affect the creep behavior of directionally solidified CM247LC superalloy. Two different heat treatment schemes were conducted: (HT1) solution treatment at 1260°C for 2 h, then first aging at 1079°C for 4 h and followed by second aging at 871°C for 20 h; (HT2) solution treatment at 1230°C for 10 h, then the same aging procedure as HT1. The microstructural observations and quantitative statistical analyses indicate that heat treatments change the γ' characteristics; HT1 resulting in more regularly cuboid morphology of γ' particle and reduction of γ-γ' eutectic phase. Furthermore, the modification of γ' morphology in HT1 specimens enhanced better creep rupture life under 760°C /724MPa creep test. Within the HT1 grains, dislocation motions were restricted because of more regularly cuboid morphology of γ' particle, which was conducive to against high temperature creep deformation.