Thermal stability of retained austenite in Cr–Ni weld metals at low temperatures

Abstract

As environmental temperature decreases, the amount of retained austenite is more likely to greatly reduce due to the thermal austenite–martensite transformation caused by the decreased thermal stability of retained austenite, probably making its amount lower than the required content. In the present study, the thermal stability of retained austenite in Cr–Ni weld metals was investigated to see whether sufficient retained austenite can be maintained at low temperatures. The specific experimental procedure is as follows: briefly, the samples were cooled in turn from room temperature to 0, −20, −40, −60, −80, −100 and −196°C; the amount of retained austenite at the above temperatures was measured using X-ray diffraction. Through investigating the dependence of the content of retained austenite on temperature, it was revealed that when the content of retained austenite is <20%, retained austenite can be maintained until −196°C.

Keywords:

• Retained austenite
• Martensite transformation
• Cr–Ni weld metal
• Low temperatures

This study was carried out as a part of research activities of ‘Fundamental Studies on Technologies for Steel Materials with Enhanced Strength and Functions’ by Consortium of The Japan Research and Development Center of Metals (JRCM). Financial support from New Energy and Industrial Technology Development Organization (NEDO) is gratefully acknowledged.