Multiscale Characterization of Microstructure in Near-Surface Regions of a 16MnCr5 Gear Wheel After Cyclic Loading

• Published in: JOM (1989) Vol. 70; no. 9; pp. 1758 - 1764
• Main Authors: Medghalchi, Setareh, Jamebozorgi, Vahid, Bala Krishnan, Arjun, Vincent, Smobin, Salomon, Steffen, Basir Parsa, Alireza, Pfetzing, Janine, Kostka, Aleksander, Li, Yujiao, Eggeler, Gunther, Li, Tong
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.09.2018; Springer Nature B.V
• Subjects: 3D Nanoscale Characterization of Metals; Carbon; Cementite; Chemistry/Food Science; Chromium; Conflicts of interest; Crack initiation; Crystal structure; Cyclic loads; Deformation effects; Dependence; Earth Sciences; Elongation; Engineering; Environment; Grain boundaries; Investigations; Ion beams; Lamella; Martensite; Materials; Materials fatigue; Microstructure; Minerals; Physics; Plastic deformation; Retained austenite; Rolling contact; Sensors; Silicon; Steel; Stress concentration; Temperature; Tomography; Transmission electron microscopy; X-ray diffraction
• ISSN: 1047-4838; 1543-1851
• DOI: 10.1007/s11837-018-2931-z

The dependence of the microstructure on the degree of deformation in near-surface regions of a 16MnCr5 gear wheel after 2.1 × 10 6 loading cycles has been investigated by x-ray diffraction analysis, transmission electron microscopy, and atom probe tomography. Retained austenite and large martensite plates, along with elongated lamella-like cementite, were present in a less deformed region. Comparatively, the heavily deformed region consisted of a nanocrystalline structure with carbon segregation up to 2 at.% at grain boundaries. Spheroid-shaped cementite, formed at the grain boundaries and triple junctions of the nanosized grains, was enriched with Cr and Mn but depleted with Si. Such partitioning of Cr, Mn, and Si was not observed in the elongated cementite formed in the less deformed zone. This implies that rolling contact loading induced severe plastic deformation as well as a pronounced annealing effect in the active contact region of the toothed gear during cyclic loading.