MANUAL Published: 01 November 2022
MNL8320200012

Chapter 10 | Stainless Bearing Steels

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Corrosion resistance is imparted to rolling bearing steels by the addition of a minimum of approximately 14 wt.% of chromium to the composition and substitution of carbon by nitrogen. Applications requiring enhanced corrosion resistance and good cryogenic properties use steels with both chromium and nitrogen alloying. Corrosion properties are affected by the applied steelmaking and heat treatment. Steelmaking processes based on powder metallurgy and hot isostatic pressing are of relevance to rolling bearing steel technologies (see later chapter of this book covering powder metallurgy). Corrosion testing methods vary from relatively simple corrosive medium immersion tests (NAVY) to advanced corrosion rate testing using anodic polarization (AP) and electrochemical impedance spectroscopy (EIS). ASTM G5-14(2021), Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements, can be used to prepare AP curves to compare corrosion resistant rolling bearing steels. A reasonable correlation is found for the NAVY versus EIS testing of rolling bearing steels. The ASTM standard test methods such as ASTM G61 and ASTM B117 are useful methodologies in characterization of rolling bearing steel corrosion resistance. Numerous lower carbon alternatives exist to the traditional 440C rolling bearing corrosion resistant steel grade. The best corrosion resistance is obtained by nitrogen alloying, particularly if secondary hardening is required for high temperature hardness retention. Hot hardness is the dominant feature of rolling bearing in aerospace rolling bearing applications. For this a new generation of stand-still corrosion resistant high temperature rolling bearing steels, based on solution-nitriding, needs to be considered. The downside of enhancement of corrosion resistance, by removal of large chromium carbides from the microstructure, is a loss of abrasive wear resistance. The aerospace rolling bearing challenge of high temperature strength and toughness in combination with standstill corrosion resistance coupled with abrasive contaminate lubricant tolerance requires innovative steelmaking and heat treatment technologies as explained in Chapter 17 of this book.

Author Information

Beswick, John, M.
CEng FIMMM, Montfoort, NL
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Pages: 195–207
DOI: 10.1520/MNL8320200012
ISBN-EB: 978-0-8031-7151-0
ISBN-13: 978-0-8031-7150-3