| Abstract Scope |
Grade 91 (G91) steel is a modified 9Cr-1Mo ferritic/martensitic steel with MX and M23C6 as strengthening particles, which is widely used in conventional and nuclear power plants for its superior creep properties. However, the service life reduction due to welding is commonly observed but not well understood. For welded G91, the fusion zone, heat-affected zone, and base metal exhibit distinct microstructure characteristics, including phase constitution, precipitates, grain size, dislocation density, etc., which may not fully recover to the initial microstructure via traditional post-weld heat treatment. Current work utilizes the Integrated Computational Materials Engineering Design (ICMD®) tool and microstructure maps to study the location-specific microstructure and mechanical property evolution throughout autogenous welding, post-weld heat treatment, and an in-situ integrated welding and thermal process developed by KVA Technologies. The sensitivity of the microstructure to composition and process conditions is also evaluated to support materials/process design, optimization, and qualification. |