| Title |
Microstructure and Mechanical Properties of Friction-Welded 12Cr FM-ODS Steel and 9Cr FMS |
| Authors |
정승문(Seungmun Jung) ; 서주원(Joowon Suh) ; 정원종(Wonjong Jeong) ; 이창규(Chang-Kyu Rhee) ; 류호진(Hojin Ryu) ; 강석훈(Suk Hoon Kang) |
| DOI |
https://doi.org/10.3365/KJMM.2026.64.10.859 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Oxide dispersion strengthened steel; Friction welding; Dissimilar metal joining; Ferritic-martensitic steel; Dynamic recrystallization |
| Abstract |
In this study, friction welding was successfully applied to fabricate dissimilar joints between 12Cr ferritic-martensitic oxide dispersion strengthened (12Cr FM-ODS) steel and commercial 9Cr ferritic-martensitic steel (9Cr FMS). The resulting microstructural evolution, crystallographic texture, and mechanical properties were systematically investigated in both the as-welded state and after post-weld heat treatment (PWHT) at 750 °C for up to 100 h. Microstructural observations revealed that the joint region was clearly divided into a dynamic recrystallization zone (DRZ), a thermo-mechanically affected zone (TMAZ), and the respective base metals. The DRZ exhibited a refined microstructure composed of ultrafine equiaxed grains with a high fraction of high-angle grain boundaries (>15°), induced by severe plastic deformation and dynamic recrystallization during welding. Electron backscatter diffraction (EBSD) analysis demonstrated that a characteristic shear deformation texture (<111>//TD and <110>//SPN) developed in the weld zone, overriding the initial extrusion texture of the ODS base metal. During prolonged PWHT, the 12Cr FM-ODS steel side exhibited outstanding microstructural stability with negligible grain growth, owing to the effective Zener pinning effect of finely dispersed Y2O3 nanoparticles. Conversely, the heat-affected zone on the 9Cr FMS side experienced significant grain coarsening and a phase transformation from martensite to ferrite, which caused a marked reduction in local hardness by approximately 70% after 100 h. Despite this localized softening, uniaxial tensile tests performed at room temperature, 400 °C, and 500 °C demonstrated that all specimens consistently fractured in the 9Cr FMS base metal, well away from the weld interface. These findings demonstrate the structural integrity and excellent thermal stability of the dissimilar joint, confirming that friction welding is a highly promising solid-state joining technique for ODS steels in advanced nuclear structural applications. |