Affiliation:
1. Institute of Superalloys Science and Technology, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
2. Institute of Advanced Power Research, Hangzhou Steam Turbine Engineering Co., Ltd., Hangzhou 310022, China
Abstract
The effects of heat treatment (H1 and H2) on the creep behavior and microstructures of Mar-M247 at 871 °C/250 MPa are studied. The results show that the as-cast microstructure is composed of eutectics, γ phase, γ’ phase, MC and M23C6 carbides, while new M6C appears in heat-treated microstructures, indicating the transformation of carbides after heat treatments. The Mar-M247 is excellent, with over 1500 h of creep life, and H1 is 48% higher than H2. The addition of post-brazing and diffusion heat treatment in H2 is detrimental to creep resistance; the two steps promoted the transformation of MC into M23C6 in advance. The increase and coarsening of M23C6 would consume more γ-phase-forming elements, weakening the solution strengthening at grain boundaries. As a result, the resistance of the grain boundary and γ/γ’ interface to dislocation motion is significantly reduced, leading to the cracks’ initiation and propagation along the grain boundaries.
Funder
Key Basic Research Program of Zhejiang Province
Zhejiang Provincial Natural Science Foundation of China
Subject
General Materials Science,Metals and Alloys