Improvement of stress-rupture life of GTD-111 by second solution heat treatment

An added second solution heat treatment was conducted to investigate its effects on the microstructures and stress-rupture properties of GTD-111. The microstructures were analyzed by scanning electron microscope after each step of heat treatments. The stress-rupture life of GTD-111 dramatically increases from about 180 to 288h at 871°C/310MPa after adding a second solution heat treatment. The added second solution heat treatment promoted the solution of γ-γ' eutectic into γ matrix, and facilitated the nucleation and precipitate of the secondary γ' particles. The distribution of γ' phase becomes much denser, the width of γ matrix channel is also reduced, and the volume fraction of γ' phase significantly increases from about 29.3% to 44.2%. The improved stress-rupture life is primarily due to the increased volume fraction of γ' phase. The carbides mainly consist of MC and a small amount of M 23C 6, which may prevent the dislocation moving and/or grain boundary sliding, and further improve the stress-rupture properties of GTD-111. © 2012 Elsevier Ltd.