Combining hardness measurements of a heat-treated crankshaft bearing with cross-sectional residual stress and retained austenite distributions measured by HEXRD. (December 2022)

• Record Type: Journal Article
• Authors: Mevec, Daniel G.; Jászfi, Vince; Prevedel, Petri; Todt, Juraj; Maawad, Emad; Keckes, Jozef; Raninger, Peter
• Is Part Of: Materials today communications. Volume 33(2022)
• Publication Date: 2022-12
• Subjects: Induction hardening -- Surface hardening -- Residual stress -- Synchrotron -- High energy X-ray diffraction -- Residual austenite; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2022.104267
• Languages: English
• ISSNs: 2352-4928

Abstract

Abstract: Surface hardening is commonly used to modify mechanical properties of crankshaft bearings. In this work, residual stress and hardness distributions across the crankshaft bearings cross-sections are evaluated using synchrotron high-energy X-ray diffraction and hardness testing. It is shown that the measured hardening depth correlates with a point of sudden sharp reversal of the stress gradient from compressive to tensile. This point is linked to the microstructure and does not shift with subsequent tempering or trimming of the sample. The superimposed data is used to interpret the evolution of stresses during the quenching and tempering cycle and gain understanding of the hardening process for such complex geometries. Within the hardened zone retained austenite is found to increase with depth to over 15 %, which is attributed to reduced quenching effects as the material is further away from the surface. All measured properties agree in the determined hardening depth of 3.5 mm to 4.5 mm, which in turn fits well with optical evaluation of metallographic microsections. Graphical abstract: Highlights: Hardness, stress and austenite gradients show identical hardening effect depth. Distinctive jumps in residual stress occurred at the hardening depth. These stress jumps show little influence from tempering or global strain relief. Retained austenite content rose unexpectedly up until the hardening depth.