Metallurgical challenges and solutions in repair welding of Cr-Co alloyed steels: a case study on gas turbine stator rings
In this study, the susceptibility of Cr-Co alloyed steels to form retained austenite during repair welding, which can adversely impact material properties, was investigated. The primary focus was to reduce the formation of retained Austenite by raising the preheat temperature above the Martensite start temperature and incorporating a Martempering thermal cycle during the repair process. This approach was intended to ensure uniform temperature distribution throughout the material thickness, thereby preventing the formation of retained Austenite, which could transform into brittle Martensite during the tempering step. Additionally, the use of elevated preheat temperatures, along with Post-Weld Heat Treatment (PWHT) at 625-660°C for 2 hours, significantly minimized the risk of hydrogen-induced cold cracking.