This study investigated the effect of postweld heat treatment (PWHT) conditions on Type IV failure behavior of 10% Cr martensitic steel welds using Haynes 282 filler. The welded joints were subjected to PWHT at temperatures of 688, 738, and 788 °C for 4 and 8 h. Creep tests were carried out at 600 °C under a stress of 200 MPa. The as-welded joint without PWHT showed Type IV cracking due to growth of voids around Laves phase by localized creep deformation in the intercritical heat-affected zone (ICHAZ). The creep properties of the PWHTed joints at 688 °C were similar to those of the as-welded joints without PWHT. On the other hand, the PWHTed joints at 738 °C exhibited a significantly longer creep life by a lower amount of Laves phase in the ICHAZ than those at 688 °C; this could be a result of the homogenization of ICHAZ microstructure during PWHT at 738 °C. However, the PWHT at 688 and 738 °C showed the same Type IV creep failure mode. Meanwhile, the PWHTed joints at 788 °C exhibited the shortest creep life in this study. The failure location was shifted to the base metal away from the HAZ, and severe plastic deformation occurred due to the softened matrix by excessive tempering.

The effect of aging heat treatment conditions on the mechanical properties and microstructure of the base and weld metal of Alloy 282 superalloy was investigated. The aging heat treatment conditions employed in this study were as follows: two-steps (1010 °C for 2 hours plus 788 °C for 8 hours) and one-step at 788 °C, 738 °C, and 688 °C for 4 hours. The base metal with the one-step aged condition exhibited lower hardness but longer creep life than that treated with the two-step aged condition. The base metal subjected to the two-step aging exhibited the highest hardness and the shortest creep life, mainly due to the precipitation of Mo-rich M6C-type carbides and coarse <i>γ</i>' (Ni3(Al,Ti)) phase. For the weld metal, regardless of aging heat treatment conditions, creep elongation and life decreased significantly compared to the base metal, due to the coarse effective grain size and inhomogeneous distribution of <i>γ</i>' precipitates.

This study investigated the microstructural evolution of the weld interface and creep fracture behavior of 10% Cr martensitic steel welds using Haynes 282 filler metal. The welded joints were subjected to post-weld heat treatment (PWHT) at temperatures of 738 °C for 4, 8, and 15 h. Creep tests were carried out at 600 °C under stress of 200 MPa. The creep rupture life increased with an increase in holding time for PWHT up to 8 h compared to the as-welded condition. However, when the holding time for PWHT was further increased to 15 h, creep properties (i.e., rupture life and creep strain) decreased considerably, and the failure location was found to shift from the ICHAZ to the weld interface. The microstructural investigation revealed that Type I carbides precipitated at the weld interface and recrystallized grains with Cr depletion were formed near Type I carbides in the partially mixed zone during creep exposure. The creep failure at the weld interface began on the surface and propagated inward through the recrystallized grains of the weld-interface region.

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