A critical understanding on the microstructure and creep failure of Super304H/T92 dissimilar multilayer welds

Dissimilar welds between austenitic stainless steel Super304H and ferritic-martensitic steel T92 were produced using hot-wire gas tungsten arc welding employing ErNiCrFe-7A fillers. The welds were post-weld heat-treated (PWHT) at 760 degrees C for 2 h and subjected to creep testing at 650 degrees C and 120 MPa. The weld microstructures were characterized in detail in the as-welded, PWHTed, and crept conditions. The creep failures were observed to take place in the fine-grained heat-affected zone (FGHAZ) of alloy T92. Microstructural studies clearly revealed accelerated degeneration of martensitic lath structure, coarsening of chromium-rich carbides, and formation of detrimental Laves phase in the FGHAZ of alloy T92. The reasons for the accelerated microstructural degradation in the FGHAZ of alloy T92 are discussed in detail.

Automated summary

This study investigated the dissimilar welds between austenitic stainless steel Super304H and ferritic-martensitic steel T92 using hot-wire gas tungsten arc welding method. The welds were post-weld heat-treated and subjected to creep testing. Microstructural analysis revealed accelerated degradation in the fine-grained heat-affected zone of alloy T92, leading to creep failures.