An Experimental Evaluation of Micro-pitting Performance of Two Bearing Steels
This experimental study focuses on the impact of operating conditions including entraining speed, sliding ratio, and load on micro-pitting performance of two typical bearing steels. Case hardened roller specimens made of alloy 9310 and through-hardened roller specimens made of alloy 485-2 are procured. Test matrices are defined according to the Latin Hypercube Space Filling Design of Experiment approach and executed to evaluate the micro-pitting performance of both materials by manipulating the speed, sliding ratio, load, and material. A two-disk test set-up is used for this purpose with each test documented by initial, interim, and final roughness, wear, and micro-pitting measurements. Before each test, a run-in process is implemented for the purpose of surface roughness break-in. By counting the distributed micro-pitted areas on the surface, a Micro-pitting Severity Index (MSI), defined as the ratio of the total micro-pitted area to the entire inspection area, is quantified for every test condition. Results indicate that the 9310 specimens showed significantly better resistance to micro-pitting compared to the 485-2 specimens, with nearly ten times lower MSI values. The data collected in this study establishes a database for micro-pitting failure of these two steel alloys that is required for validation of point contact lubrication models with circumferentially oriented surface roughnesses.
Engineering, Mechanical Engineering, Materials Science, Micro-pitting, micro-pit, elastohydrodynamic lubrication, ground specimens, surface failure
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