SYMPOSIA PAPER Published: 01 January 2024

The Necessary Fine-Tuning of Process Management and Controls for Metallic Transformations during Manufacturing of Bearings: Application to M50NiL Steel


Steel components of bearings or constant velocity joint (CVJ) products are produced to meet numerous and sometimes conflicting requirements, such as performance, cost efficiency, quality, and carbon footprint or prosperous human development. Automotive, industry, and aerospace applications are all concerned with these challenges. The several steps of the manufacturing process must therefore be thoroughly understood and controlled to ensure the right level of targeted parameters at the right cost. For this purpose, studies have dealt with practical examples of such fine-tuning, considering fine metallurgical studies, methodology of controls, from the laboratory stage to the mass production stage. The present study deals with these issues in relation to case-carburized M50NiL steel to find the practical link between research and development and each manufacturing step, with the focus on the core and surface properties of components. In particular, grain size, residual stress profiles, microstructure, and precipitation were investigated due to their impact on the life duration of aerospace bearings. We first conducted a preliminary review of the existing literature containing published and quantitative data regarding the M50NiL grade. Then a test plan was carried out, and the results were analyzed using a thermodynamic approach and a quantitative analysis of precipitation linked to the manufacturing steps. The result was a better understanding of residual stress and core microstructure, making fine-tuning easier to achieve and adapt to customer demands. These results were obtained thanks to the efficient cooperation between metallurgists and manufacturing teams in considering the time to market for new developments.

Author Information

Dubois, Pierre-Emmanuel
NTN EUROPE, Research Innovation Development, Annecy, FR
Perrard, Fabien
NTN EUROPE, Research Innovation Development, Annecy, FR
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Pages: 329–359
DOI: 10.1520/STP164920230016
ISBN-EB: 978-0-8031-7746-8
ISBN-13: 978-0-8031-7745-1