Microstructure and phase composition of transition zone between low alloyed steel boiler tube and an austenitic stainless steel weld overlay produced by cold metal transfer method

The microstructural characterization, as well as phase and chemical composition of the transition zone between the 16Mo3 steel boiler tube and 310 austenitic stainless steel weld overlay produced by the Cold Metal Transfer method, were studied. It was showed that the transition zone has a complex structure related to the changing composition. Two separate areas are noticeable in the transition zone. The area near the fusion boundry is two phased (martensite and austenite). Detailed TEM investigation of this area disclosed martensitic–austenitic structure with the Kurdjumov-Sachs relationship between martensite and austenite. The microstructure of the part of the transition zone with Ms temperature lower than room temperature is austenite. The investigations showed that by using low energy welding method we can significantly reduce the width of the martensite area in the transition zone of weld overaly.