Heat Treatment Effects on the High Temperature Mechanical Behavior of Directionally Solidified Mar-M247 Superalloy

In this study, two heat treatment schemes were proposed to study the high temperature mechanical behavior of directionally solidified MAR-M247 superalloy with withdraw rate of 180 mm/h. Standard heat treatment (HT1) procedures are solution treatment at 1230°C for 2 h/GFQ, then first aging at 980°C for 5 h/AC and followed by second aging at 870°C for 20 h/AC. Modified heat treatment (HT2) is solution treatment at 1260°C for 3 h/GFQ and first aging at 980°C for 6 h/AC, then the same second aging procedure. Uneven size and shape of gamma prime precipitates are observed after full HT1 scheme, whereas even size but fusion-alike gamma prime precipitates are observed in HT2 specimen. Creep tests at high temperature/low stress (982°C/200MPa) conditions show similar creep rupture life but low extension rate of HT1 specimen. Uneven size and shape of gamma prime precipitates of HT1 specimen effectively prevent dislocation motion. However, the yield strength, tensile strength and elongation to failure of HT2 specimens at 982°C are higher than these of HT1 specimens.