pISSN : 1598-706X / eISSN : 2288-8381
한국주조공학회지 (37권5호 139-147)
The Effect of Thermal Exposure on the Microstructural Evolution and Tensile Properties in Cast Hastelloy X
Hastelloy X 주조재의 열간 노출에 따른 미세조직 및 인장 특성 변화
Baig Gyu Choi†, In Soo Kim, Jeonghyeon Do, Joong Eun Jung, In Yong Jung, Hyun Uk Hong* and Chang Yong Jo
High Temperature Materials Department, Korea Institute of Materials Science, *Department of Materials Science and Engineering, Chanagwon National University
Microstructural evolution of cast Hastelloy X during thermal exposure has been investigated. OM, SEM, and TEM microscopy were carried out on the as-cast, the standard heat treated, and the thermally exposed conditions. Tensile tests were also conducted to understand the effect of microstructural evolution on the degradation of tensile properties. Coarse M6C and fine M23C6 carbides were found in as-cast Hastelloy X with fine carbides on sub-boundary. Some of M23C6 carbide dissolved i into the matrix during solution heat treatment and dislocation network formed at the i interface between the carbide and the matrix due to the misfit strain. There was no significant microstructural difference between the exposed specimens at 400oC and the solution heat treated specimen. A large amount of M23C6 carbides precipitated along and near grain boundaries and sub-boundaries after exposure at 650oC. Exposure at 870oC of the alloy caused precipitation of M6C and μ. The strength increased and the elongation decreased by thermal exposure at 650oC and 870oC because carbides interfere with the movement of the dislocation. It was found that the precipitation of carbide gave significant effects on the tensile properties of Hastelloy X.
Hastelloy X, Thermal exposure, Carbide, Microstructure, Tensile properties
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