Abstract
In this work, dissimilar rotary inertia friction welds between 422 martensitic stainless steel and 4140 martensitic low-alloy steel were made to fabricate prototype heavy-duty diesel engine pistons. The influence of the inertia friction welding process and post weld heat treatment (PWHT) temperature on the interfacial microstructure evolutions and corresponding effects on mechanical properties of the 422/4140 welds were evaluated in detail. Carbon diffused from the 4140 side to the 422 side during PWHT at 650 °C for 1.5 h, causing the formation of a hard carbide-rich layer on the 422 side, and a softer but discontinuous C-depleted layer the 4140 side. PWHT at 700 °C for 1.5 h greatly accelerated C diffusion across the interface relative to 650 °C, resulting in a thicker hard carbide-rich layer and a relatively thick and continuous layer of coarse C-depleted grains (ferrite) on the 4140 side. In addition, the PWHT temperature greatly influenced the tensile properties and fracture behavior of the welds, with the 650 °C PWHT-ed samples failing predominately in a ductile manner in the 4140 heat affected zone during tensile testing. Conversely, the 700 °C PWHT specimens exhibited a strength reduction compared with the 650 °C PWHT specimens because of additional coarsening of the interfacial ferrite layer and softening of the base materials during PWHT, with brittle fracture between the hard and soft layers the predominate failure mechanism. Based on the findings, a reduced PWHT temperature and/or time, minimizing the hardness differential of the base metals, and pre-heating the 422 steel prior to welding are the potential pathways to achieve a more optimal balance between desirable tempering and stress relief of the weld microstructure and undesirable C migration across the weld interface, and to reduce the strength mismatch across the weld.
Original language | English |
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Article number | 145607 |
Journal | Materials Science and Engineering: A |
Volume | 885 |
DOIs | |
State | Published - Oct 3 2023 |
Funding
The authors acknowledge Dustin Heidel and Victoria Cox for metallography, and Ian Stinson for tensile tests. Research was in part sponsored by the Powertrain Materials Core Program, under the Propulsion Materials Program (managed by Jerry Gibbs) in the Department of Energy, Vehicle Technologies Office, United States. The information, data, or work presented herein was conducted in part as an Advanced Vehicle Power Technology Alliance (AVPTA) “Extended Enterprise” project funded by the U.S. Army Ground Vehicle Systems Center (GVSC), U.S. Department of Defense, Department of the Army. AVPTA is chartered under the auspices of the U.S. Department of Energy/U.S. 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 the 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 Mr. Roger Miller and Dr. Janet Meier for the useful discussion and technical paper review. The authors acknowledge Dustin Heidel and Victoria Cox for metallography, and Ian Stinson for tensile tests. Research was in part sponsored by the Powertrain Materials Core Program, under the Propulsion Materials Program (managed by Jerry Gibbs) in the Department of Energy, Vehicle Technologies Office, United States . The information, data, or work presented herein was conducted in part as an Advanced Vehicle Power Technology Alliance (AVPTA) “Extended Enterprise” project funded by the U.S. Army Ground Vehicle Systems Center (GVSC), U.S. Department of Defense, Department of the Army. AVPTA is chartered under the auspices of the U.S. Department of Energy/U.S. 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 the 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 Mr. Roger Miller and Dr. Janet Meier for the useful discussion and technical paper review.
Keywords
- 4140 martensitic low-alloy steel
- 422 martensitic stainless steel
- Diesel engine pistons
- Dissimilar metal weld
- Interfacial microstructure
- Mechanical properties
- Rotary friction welding