About this Abstract |
| Meeting |
2025 AWS Professional Program
|
| Symposium
|
2025 AWS Professional Program
|
| Presentation Title |
Effect of Post Weld Heat Treatment on Microstructure and Mechanical Properties of Rotary Inertia Friction Welded Dissimilar 422/4140 Martensitic Steel Piston Joints |
| Author(s) |
Yiyu Wang, Katherine Sebeck, Eric Gingrich, Michael Tess, James Haynes, Dean Pierce |
| On-Site Speaker (Planned) |
Yiyu Wang |
| Abstract Scope |
In this work, dissimilar Grade 422 martensitic stainless steel and AISI 4140 medium carbon steels were welded for fabricating heavy-duty diesel engine pistons using rotary inertial friction welding (RIFW) process. Effect of post-weld heat treatment (PWHT) on microstructure and mechanical properties of this 422/4140 weld were systematically investigated via multi-scale characterization and integrated in-situ testing technique. The results shows a fully martensite microstructure with high hardness formed at the interface across this 422/4140 joint after welding. Increasing the PWHT temperature from 525 °C to 700 °C significantly reduced the high hardness of sub-regions across the weld interface, especially thermo-mechanical affected zones (TMAZ) and heat-affected zone (HAZ) on both sides. The 422 side exhibited a higher tempering resistance with less hardness reduction than the 4140 side. The 422-TMAZ maintained a high hardness as high as 550 HV until the PWHT temperature went beyond 600 °C. A thin layer of un-tempered martensite grains in the 422-TMAZ was retained until 625 °C. Microstructural and chemical analyses show the element migration across the weld interface, including carbon, was limited when the PWHT temperature was 600 °C and below. A notable carbon migration from 4140 side to 422 side occurred in the 625 °C-PWHT and 700 °C-PWHT specimens. A carbide-rich eutectoid layer on 422-TAMZ and carbon-depleted ferrite on the 4140-TMAZ formed in the 700 °C-PWHT specimen. The toughness of the welds was evaluated using the three-point bend tests utilized with in-situ digital image correlation (DIC) measurements. The as-welded specimen failed at HAZ with the highest displacement and load force. All the PWHT-ed specimens failed at or near the weld interface with decreased displacement and peak load. DIC measurements reveal highly concentrated deformation occurred in the HAZ, especially 4140 side, in the as-welded specimen and low-temperature PWHT-ed specimens. A high strain was observed in both 4140 TMAZ and HAZ of the 700 °C specimen. The different tempering resistance of 422 and 4140 oscillated this deformation behavior. Based on this study, the inhomogeneity and inconsistence between the interface hardness and toughness/deformation needs to be considered when selecting a PWHT temperature. |
| Proceedings Inclusion? |
Undecided |