Dissimilar 2·25Cr/9Cr and 2Cr/0·5CrMoV steel welds: Part 2: Identification of precipitates

摘要

The long range diffusion of rapidly diffusing elements in dissimilar welds, which occurs during heat treatment and in service exposure, initiates heavy microstructural changes on both sides of the weld. Various carbides and nitrides either dissolve or precipitate as a function of the distance from the fusion line. The type and amount of these particles can be predicted by a numerical method for solving problems of simultaneous precipitation and diffusion. Predicted precipitate distributions for a 2·25Cr/9Cr and a 2Cr/0·5CrMoV weld are verified using experimental data obtained with analytical and energy filtering transmission electron microscopy. The phase diagrams for the high chromium side and the low chromium side of the welds are evaluated and compared with the experimentally determined precipitate distribution.