Crystallographic slip transfer during creep crack growth in weldments of Fe-Cr-Ni-Mo (N) type steel.

This study reports the crystallographic analysis on sample extracted from the Creep Crack Growth (CCG) tested (873 K with a notch in the centerline of weld region) specimen in order to add further understanding to crystallographic slip initiation responsible for strain localization in a different zone of weldment in the vicinity of the crack tip. The microtexture evolution in the quest of strain distribution has been compared for creep cracked and weldment of the as-received specimen. A coarsening of dendrites in the thickness direction and intragrain strain localization are found to be evident in fusion zone (FZ) unlike a stable microstructure in the base metal region with strain distribution along the grain boundary. Further, an evolved procedure is adopted to assess the crystallographic slip plane in different regions of a weldment. It has been observed that slip plane of (111) type, with an average deviation angle of 6°, is dominant in the base metal region of equiaxed grains microstructure. However, the grains grown epitaxially from the base metal to FZ has shown a preferential of slip plane transfer from (111) to (001) type in contrast to (001) type slip planes with average deviation angle 2° in FZ. [ABSTRACT FROM AUTHOR]