SYMPOSIA PAPER Published: 01 January 2024
STP164920220097

Development of the Cost-Efficient Steel 18MnCrMoV4-8-7 for Case-Hardening or Carbonitriding of Mid-Sized Roller Bearings

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The state-of-the-art case-hardening steels for bearings with intermediate wall thickness up to approximately 100 mm are SAE 3311 (≈ 12NiCr14-6) and 18NiCrMo14-6. However, they have several detrimental features. The financial and environmental costs of the raw material (mainly attributed to the nickel [Ni] content of approximately 3.5 wt%) and for the carburizing treatment for the SAE 3311 are very high, and the performance potential often suffers from an unsatisfactory microscopic degree of cleanliness. To replace them, a steel was developed with the following target properties: a comparable or better hardenability curve than SAE 3311; a Ni content significantly below 1 wt% to reduce cost and greenhouse-gas emissions; a hardness higher than 61 HRC after carbonitriding, hardening, and regular tempering for larger samples; and a significantly reduced alloying surcharge compared to SAE 3311. Our development approach included a virtual alloy design phase using thermodynamic calculations in combination with time-temperature-transformation simulations, casting of two different candidate alloys for experimental investigation, in-depth characterization of the casted alloys after various heat treatments, assessment of (rotating-bending) fatigue behavior, and bearing-lifetime testing. The newly developed steel 18MnCrMoV4-8-7, which is essentially a low-carbon (i.e., case-hardening) variant of the established through-hardenable bearing steel 100CrMnMoSi8-4-6, has a significantly lower Ni content than SAE 3311 and is therefore not only less expensive but also more environmentally friendly while offering a similar hardenability. 18MnCrMoV4-8-7 transforms into bainite over a wide range of cooling rates and consequently exhibits a good predictability of dimensional or distortion behavior. 18MnCrMoV4-8-7 shows similar or better rotating-bending and rolling-contact fatigue behavior than both 100Cr6 and SAE 3311. The first bearings with rings made from 18MnCrMoV4-8-7 have been successfully brought into application.

Author Information

Moeller, Johannes
Schaeffler Technologies AG & Co. KG, Schweinfurt, DE
van Soest, Frank
Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Krefeld, DE
Trojahn, Werner
Schaeffler Technologies AG & Co. KG, Schweinfurt, DE
Werner, Michael
Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Krefeld, DE
Dinkel, Markus
Schaeffler Technologies AG & Co. KG, Schweinfurt, DE
Krull, Hans-Guenter
Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Krefeld, DE
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Details
Pages: 17–28
DOI: 10.1520/STP164920220097
ISBN-EB: 978-0-8031-7746-8
ISBN-13: 978-0-8031-7745-1