A precipitation hardenable semi-austenitic stainless steel AISI 632 grade was austenitized according to industrial specifications and thereafter subjected to isothermal treatment at sub-zero Celsius temperatures. During treatment, austenite transformed to martensite. The isothermal austenite-to-martensite transformation was monitored in situ by magnetometry and data was used to sketch a TTT diagram for transformation. As an alternative treatment, after austenitization the material was immersed in boiling nitrogen and up-quenched to room temperature by immersion in water prior to be subjected to isothermal treatment. Magnetometry showed that the additional thermal step in boiling nitrogen yields a minor increment of the fraction of martensite, but has a noteworthy accelerating effect on the transformation kinetics, which more pronounced when the isothermal holding is performed at a higher temperature. Data is interpreted in terms of instantaneous nucleation of martensite during cooling followed by time dependent growth during isothermal holding.
|Title of host publication||Heat Treating 2015: Proceedings of the 28th ASM Heat Treating Society Conference|
|Number of pages||5|
|Publication status||Published - 2015|
|Event||28th ASM Heat Treating Society Conference - Detroit. MI, United States|
Duration: 20 Oct 2015 → 22 Oct 2015
Conference number: 28
|Conference||28th ASM Heat Treating Society Conference|
|Period||20/10/2015 → 22/10/2015|
Villa, M., Hansen, M. F., & Somers, M. A. J. (2015). The sub-zero Celsius treatment of precipitation hardenable semi-austenitic stainless steel. In Heat Treating 2015: Proceedings of the 28th ASM Heat Treating Society Conference (pp. 431-435). ASM International.