Interfacial microstructure and mechanical properties of rotary inertia friction welded dissimilar 422 martensitic stainless steel to 4140 low alloy steel joints

• DOI: 10.1016/j.msea.2023.145607
• Publication Date: 2023-08-23T23:52:37Z
• Authors: Yiyu Wang; Katherine Sebeck; Michael Tess; Eric Gingrich; Zhili Feng; James A. Haynes; Michael J. Lance; Govindarajan Mura...; Randall Marchel; Thomas Kirste; Dean Pierce
• Keywords: Brittleness

In this work, dissimilar rotary inertia friction welds between 422 martensitic stainless steel and 4140 low-alloy were made to fabricate prototype heavy-duty diesel engine pistons. The influence of the welding process post weld heat treatment (PWHT) temperature on interfacial microstructure evolutions corresponding effects mechanical properties 422/4140 evaluated in detail. Carbon diffused from side during PWHT at 650 °C for 1.5 hours, causing formation a hard carbide-rich layer side, softer but discontinuous C-depleted side. 700 hours greatly accelerated C diffusion across interface relative °C, resulting thicker relatively thick continuous coarse grains (ferrite) addition, influenced tensile fracture behavior welds, with PWHT-ed samples failing predominately ductile manner affected zone testing. Conversely, specimens exhibited strength reduction compared because additional coarsening ferrite softening base materials PWHT, brittle soft layers predominate failure mechanism. Based findings, reduced and/or time, minimizing hardness differential metals, pre-heating prior are potential pathways achieve more optimal balance desirable tempering stress relief undesirable migration interface, reduce mismatch weld.