Cross-weld creep performance in grade 91 steel: Macro-based assessment

Meaningful characterization of the microstructure in metallurgically complex steels is complicated by the diversity of thermal cycles experienced by multipass fusion welds. To overcome the problems of relevant documentation, it is necessary to balance information from macro-, micro-, and nano-evaluation with appropriate analysis. This paper presents details regarding recommended approaches that optimize this characterization. Initially, specific procedures relevant to macroanalysis, including hardness mapping and calculation of the peak temperature through the width of the heat-affected zone (HAZ), are described. Then, assessment of the distribution of creep damage in feature-type, cross-weld creep tests using laser microscopy is detailed. Using these methods, the extent of damage through the HAZ was compared to the local reduction in the HAZ hardness and to the calculated peak temperatures in the HAZ. The implications of these findings are discussed with respect to damage, deformation, and sample geometry.