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Subsurface Microstructure Evolution and Residual Stress in 42CrMo4 Steel after Single-Pass Pendulum Tests

Janis S. Kimm 1, Fabian Pöhl 2, Petra Wiederkehr3, and Werner Theisen 2
1. Ruhr-Universität Bochum, Bochum, Germany
2. Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany
3. Technische Universität Dortmund, Emil-Figge-Straße 50, 44227 Dortmund, Germany

Abstract— This work investigates the effect of cutting on the microstructure and subsurface properties of a cut specimen, with particular focus on the influence of the sample’s microstructure and its evolution. Single-pass pendulum tests were conducted with samples of 42CrMo4 steel that had been subjected to different heat treatments. The subsurface region after cutting was analyzed optically by SEM and EBSD. The strain hardened surface region was investigated by nanoindentation. It was found that a soft-annealed structure, in particular, was altered deeply by cutting, resulting in a hardness increase as well as an microstructure that is elongated and refined by high shear deformation microstructure in near-surface regions. The strain hardening behavior and potential of a microstructure had a striking influence on the subsurface alteration. Although some microstructures yielded the same forces under equal cutting conditions, the subsurface alteration was different. This type of change in microstructure was correlated with the micromechanical properties and residual stresses. General influences, such as cutting depth, on the alteration of microstructures by cutting were also taken into account.

Index Terms—machining, subsurface microstructure, residual stress, nanoindentation, EBSD

Cite: Janis S. Kimm, Fabian Pöhl, Petra Wiederkehr, and Werner Theisen, "Subsurface Microstructure Evolution and Residual Stress in 42CrMo4 Steel after Single-Pass Pendulum Tests," International Journal of Mechanical Engineering and Robotics Research, Vol. 9, No. 8, pp. 1072-1080, August 2020. DOI: 10.18178/ijmerr.9.8.1072-1080