Precipitation and Growth of Precipitates in Welded Joint of High Cr Ferritic Heat Resistant Steels

摘要

This paper is aimed at investigating the difference of precipitation behavior in fine-grained heat-affected zone (FGHAZ), coarse grained heat-affected zone (CGHAZ) and base metal for welded joints of high Cr ferrite heat resisting steel. The simulated HAZ (SHAZ) specimens were used, whose SEM observation showed that the precipitates in FGHAZ specimens (1173 K) were fewer and larger than those in CGHAZ (1523 K) specimens and base metal specimens. X-ray diffraction analysis showed that the precipitates are M_(23)C_6, M_7C_3, MX, s Laves phase and μ phase. The element analysis of the extraction showed that mass percentages of Cr, W and Mo in the FGHAZ specimen are higher than those in the base metal specimen after long time aging. Finally, a 2-D model was purposed to simulate the precipitation behaviour of Laves phase.