Influence of inclusion content on rolling contact fatigue in a gear steel: Experimental analysis and predictive modelling |
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Authors: | G Donzella M Faccoli A Mazzù C Petrogalli H Desimone |
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Affiliation: | aUniversity of Brescia, Department of Mechanical and Industrial Engineering, via Branze, 38, 25123 Brescia, Italy;bTenaris Dalmine S.p.A., Piazza Caduti 6 Luglio 1944, 24044 Dalmine, Bergamo, Italy |
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Abstract: | Rolling contact fatigue tests were carried out on ring specimens made of quenched and tempered SAE 5135 gear steel with three different steel-production processes, through a bi-disc machine under pure rolling condition and water lubrication. Early formation of micro-pits then coalescing into macro-pits was observed on the rolling surface, while the final failure was caused by subsurface originated spalling phenomena. Microscope analysis of specimens section highlighted the complex surface and subsurface crack layout, and permitted to recognise sulphides as preferential sites for cracks initiation. The inclusion content was analysed throughout the extreme value statistics and the maximum expected inclusion in the Hertzian contact zone was introduced in a failure assessment diagram recently proposed, which resulted effective in predicting the specimen failures. |
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Keywords: | Rolling contact fatigue Inclusions Pitting Spalling Failure assessment diagram |
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