SYMPOSIA PAPER Published: 08 September 2020

Effect of MnS on the Micropitting Behavior of Through Hardened Bearing Steel during Rolling Contact Fatigue


In the manufacturing of bearing steel, sulfur (S) and phosphorous (P) are considered impurities because of their adverse effect on ductility and impact strength. The ASTM standard for through hardened 52100 steel limits its P and S content to 0.025 wt.%. Sulfur reacts with manganese in steel, resulting in manganese sulfide (MnS) inclusions, which are known to enhance machinability. This work contains a summary of an investigation into the influence of MnS inclusions on micropitting. Micropitting damage was produced on rolling contact fatigue test samples operated with a nondimensional film thickness (λ) lower than one. Tests were conducted on through hardened steel samples with two different sulfur contents (approximately 0.002 wt.% and 0.012 wt.% S) under 2.1 GPa maximum Hertzian contact pressure. The percentage of damaged area was measured using image analysis at intervals of one million revolutions up to a total of five million revolutions. The results indicated that the presence of MnS inclusions increases the propensity of steel to sustain micropitting damage. Detailed scanning electron microscopy/focused ion beam (SEM/FIB) and three-dimensional analyses of the MnS inclusions and micropitting damage are included.

Author Information

Bedekar, Vikram
Timken Technology Center, N. Canton, OH, US
Hager, Carl
Timken Technology Center, N. Canton, OH, US
Hyde, R., Scott
Timken Technology Center, N. Canton, OH, US
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Pages: 169–181
DOI: 10.1520/STP162320190067
ISBN-EB: 978-0-8031-7693-5
ISBN-13: 978-0-8031-7692-8