Effect of Second Aging Treatment on the Microstructure and Mechanical Properties of SUH660 Alloy

Jeoung Han Kim, Do-Hoon Kim, You-Hwan Lee
2016 Korean Journal of Metals and Materials  
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 aging treatment noticeably increased hardness and tensile strength. In particular, a secondary aging treatment at 630 °C for 24 hrs
more » ... 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 electron 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. † (
doi:10.3365/kjmm.2016.54.10.716 fatcat:ul43zj2gvjdtjngr6m2w4s74ta