Abstract
The study investigated how post-weld heat treatment (PWHT) temperature affects the microstructure and localized deformation/fracture during bend testing of rotary inertia friction welds (RIFW) between AISI 422 stainless steel and AISI 4140 steel. RIFW produced a fully martensitic interface with approximately 550 HV hardness in both the thermo-mechanically affected (TMAZ) and heat-affected zones (HAZ). Due to differences in temper resistance, the 4140 TMAZ/HAZ softened progressively under PWHT temperatures from 525 °C to 700 °C, while the 422 TMAZ unexpectedly maintained about 550 HV up to 600 °C before significantly softening at temperatures ≥625 °C. This asymmetric softening generated steep hardness gradients across the interface at temperatures ≤600 °C. Furthermore, carbon migration across the interface was minimal up to 600 °C, moderate at 625 °C, and by 700 °C produced a carbide-rich eutectoid layer in the 422 TMAZ alongside a carbon-depleted soft ferrite layer in the 4140 TMAZ. Strain during bending was PWHT-dependent, concentrating on the 4140 side; in as-welded joints, the high hardness led to deformation and crack initiation in the base metals, whereas in PWHT samples, cracking initiated in the softened 4140 TMAZ near the interface. The intermediate PWHT temperature of 625 °C offered the best balance of limited carbon diffusion across the interface, relatively low peak weld hardness and minimized hardness gradients across the interface, more homogenous deformation, and good bend test performance.
| Original language | English |
|---|---|
| Pages (from-to) | 8340-8351 |
| Number of pages | 12 |
| Journal | Journal of Materials Research and Technology |
| Volume | 39 |
| DOIs | |
| State | Published - Nov 1 2025 |
Funding
The authors acknowledge Cody Taylor and Tyler Garrett for bend test sample preparation and testing. Research was in part sponsored by the Powertrain Materials Core Program, under the Propulsion Materials Program (managed by Chris Schooler) in the US Department of Energy Vehicle Technologies Office. The information, data, or work presented herein was conducted in part as an Advanced Vehicle Power Technology Alliance “Extended Enterprise” project funded by the U.S. Army Ground Vehicle Systems Center (GVSC), U.S. Department of Defense, Department of the Army. The Advanced Vehicle Power Technology Alliance is chartered under the auspices of the US Department of Energy/US Department of Defense Memorandum of Understanding titled “Concerning Cooperation in a Strategic Partnership to Enhance Energy Security.” The research and development work was performed at Oak Ridge National Laboratory, which is managed by UT-Battelle LLC for the US Department of Energy under contract DE-AC05-00OR22725. The authors would also like to thank Roger Miller and Yukinori Yamamoto for the useful discussion and technical paper review. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). Approved for public release by U.S. Army Ground Vehicle Systems Center.
Keywords
- 4140 low-alloy steel
- 422 martensitic stainless steel
- Bend testing
- Diesel engine pistons
- Dissimilar metal weld
- Post-weld heat treatment
- Rotary friction welding