| Abstract |
| SUH660 is a precipitation hardening stainless steel which has high strength at moderately high temperature. In this study, the effect of a secondary aging-treatment after the standard 720 °C heat-treatment was investigated. The Rockwell C hardness test with detailed TEM observerations was performed to study the steel’s hardening mechanism. The additional secondary treatment noticeably increased hardness and tensile strength. In particular, a secondary aging treatment at 630 °C for 24 hrs resulted in the maximum hardness of 35.5 HRC, which is higher than the hardness of a standard heat-treated sample by around 4 HRC. A transmission election microscopy study revealed the size distribution of γ′ and h precipitates after standard aging treatment. In contrast, the precipitate was not oberserved after the 630°C secondary aging-treatment. Contrary to expectation, the γ’’ precipitate was not observed regardless of aging-treatment. The mechanism of the hardening process is discussed. |
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| Key Words |
| SUH660, superalloy, precipitation hardening, aging treatment, hardness |
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