Abstract: Dissimilar welds are playing important roles in the manufacturing of components in power stations, and carbon migration is an important factor influencing the life of dissimilar welds. The influence of carbon migration on dissimilar welds (9%Cr+2.25%Cr) is studied. A carbon-rich hard zone, adjoining the soft zone (carbon denuded zone) is also detected in the high Cr side of the welds. There is an obvious difference in hardness between the carbon rich and denuded zones. In the quasi-static fracture toughness test of HAZ of the weldment at high temperature (500 ℃), it is found that the crack propagates more easily in the carbon denuded zone. The fracture appearance of carbon-rich zone is quasi-cleavage, and the carbon denuded zone’s presents mainly dimples. Finite element analysis(FEA) indicates that plastic strain concentrates in the carbon denuded zone. The carbon denuded zone is the weaker part of toughness because of the low absorption of elastic & plastic energy.

Key words: carbon migration, dissimilar welds, finite element analysis, high temperature toughness, micro hardness