Crystallographic assessment of creep damage in high chromium steel weld joints using EBSD observation

AbstractMicrostructural change during creep damage process was investigated on the fine grained heat affected zone (HAZ) and the coarse grained HAZ of 12Cr steel casting base metal welded by 9Cr weld steel, using a scanning electron microscope with electron backscattering diffraction pattern (EBSD) equipment. Creep rupture and interrupted creep test samples were cut at mid-section along longitudinal direction and inverse pole figure, image quality and kernel average misorientation maps were obtained through EBSD observation. The measured quantities were creep void size, grain size, precipitation size, area averaged image quality value IQ ave and area averaged kernel average misorientation KAM ave. Micro Vickers hardness test was also conducted to investigate the hardness distribution across the weld joint. Among various creep damage evaluation parameters, hardness, area fraction of voids, KAM ave and area fraction of precipitates at each HAZ showed apparent changes with creep damage time fraction at HAZ p...