Thermal aging embrittlement of cast stainless steel CF-8A was evaluated by using miniature tensile specimens, Small Punch test and microstructural observation. Optical microscopic analysis, SEM and TEM observations have been carried out in this study. Aging phenomena of the ferrite phase has been identified by hardness measurements. With increase in aging time, changes in strength were observed but not in consistent manner. Despite of the decrease in strength after the prolonged aging at 400℃, no noticeable microstructural features were observed except a' phase precipitation in ferrite by spinodal decomposition. For this material, miniature tensile tests were found to have limited applicability beyond yield strength. Small Punch test and other mechanical tests showed the changes of mechanical properties similar to those of the miniature tensile tests.
주조 스테인리스강(CF-8A)의 가속열취화 현상을 Small Punch test와 microstructural observation을 이용하여 평가하였다. Optical microscopic 해석을 위해서 SEM과 TEM 관찰을 하였다. Ferrite phase의 Aging 현상은 경도 측정으로 확인되나, 강도와 Aging 시간은 일관된 거동을 보이지 않는다. 400℃ 에서의 장기 Aging에서 강도가 떨어짐에도 불구하고, phase에 의한 석출 관찰을 제외한 미시구조적인 특성을 찾지 못하였다. 또한 이 물질에서 miniature tensile test를 항복 응력 이후의 해석에 적용하기엔 한계가 있음을 발견하였다