Texture characteristics and high temperature stress relaxation behaviors of Nimonic 80A alloy bolt
MA Jian-zhong1, HUANG Yi-jun2, HUANG You-qiao3, WANG Bo2, ZHANG Ning4, MENG Li4
1. Zhejiang Zheneng Lanxi Electric Power Generation Co., Ltd., Jinhua 321199, Zhejiang, China; 2. Material Technology Department, Zhejiang Zheneng Technology Research Institute Co., Ltd., Hangzhou 311121, Zhejiang, China; 3. Equipment Management Department,Zhejiang Zheneng Lanxi Electric Power Generation Co., Ltd., Jinhua 321199, Zhejiang, China; 4. Metallurgical Technology Institute, Central Iron and Steel Research Institute, Beijing 100081, China
Abstract：The microstructure and texture characteristics of Nimonic 80A superalloy bolt were studied using SEM and EBSD techniques, meanwhile, stress relaxation behaviors at different high temperatures and the corresponding microstructure as well as texture evolution were analyzed. The results showed that no strong texture was obtained in γ phase, and no correspondence was shown between γ grain orientation and grain size. γ′ phase and Cr carbides were the main second phase in the alloy. The γ′ phase was dispersed in the matrix, while Cr carbides precipitated at grain boundaries and showed “chain” distribution along axial direction of the bolt respectively. The distribution characteristics of Cr carbides had no significant correlation with γ grain structure and orientation. Before and after stress relaxation experiments, microstructure, texture as well as the distribution of chromium carbide showed not change apparently, while γ′ phases were shown to coarsen. Under the same load, the experimental temperature influenced the stress relaxation behaviors, the higher temperature contributed to higher stress relaxation ratio, which could be related with easier dislocation slip. The phenomenon was consistent with more grains showing higher GOS(Grain Orientation Spread) values in the sample, while GOS value of individual grain did not show dependence on grain size and crystal orientation.
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2022, Vol. 32 
