Hastelloy X의 고온열화에 따른 미세구조 및 고온압축특성

Abstract

Short-term high temperature degradation test was conducted on Hastelloy X, a candidate tube material for high temperature gas-cooled reactors (HTGR), to evaluate the variation of microstructure and mechanical property in air at 1050oC during 2000h. The dominant oxide layer was Cr-oxide and a very shallow Cr-depleted region was observed below the oxide layer. At the beginning of degradation, the island shape M6C precipitate (M=Mo-rich, Fe, Ni, Cr) was observed in matrix region. After 2000h degradation, precipitate shape was changed to the chain shape and increased amount of precipitate. These results influenced mechanical property of the specimen which exposed in high temperature. Yield strength was decreased from 115MPa to 89MPa after 24h and 2000h exposure, respectively.