Investigation on solidification and phase transformation of heterogenous interface structure in dissimilar metal weld between high Cr heat-resistant steel and nickel-based alloy 617

摘要

The present study characterized heterogenous interface structure in dissimilar metal weld between a high Cr martensitic heat-resistant steel and nickel-based alloy weld metal (WM), and revealed its solidification and phase transformation processes during welding. The heterogenous interface structure consists of a martensitic peninsula structure and a partially mixed zone (PMZ) of austenitic stainless steel. The K-S relationship between peninsula structure and its surroundings indicates: 1. phase transformation of (delta-Fe) to (gamma-Fe) of peninsula occurs only after previous austenitic PMZ has solidified; 2. the subsequent WM solidifies epitaxially on (gamma-Fe) of peninsula. Due to that the liquidus temperature of PMZ is lower than that of base metal (BM), the peninsula structure can form in the early stage of solidification by quick freezing of liquid BM.