MANUAL Published: 01 November 2022
MNL8320200022

Chapter 20 | Powder Metallurgy

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Powder metallurgy was in the past synonymous with sintered and forged component production for nondemanding rolling bearing applications. State-of-the-art powder metallurgy (PM) in combination with hot isostatic pressing (HIP) is capable of producing steel qualities suitable for demanding rolling bearing components. For high speed steel (HSS) compositions, PM-HIP steelmaking can produce steel qualities equal if not better than conventional HSS steelmaking. PM-HIP steelmaking is particularly attractive for high chromium stainless steel composition due to the suppression of the troublesome large primary carbides formed during conventional melt and casting steelmaking methodologies. The isotropic properties in PM-HIP steelmaking are a particularly appealing aspect of PM-HIP steelmaking. Bearing steel powders can be produced using clean-steel melting and gas atomization. A ceramic-free process using the electrode induction gas atomization (EIGA) process has the potential to produce PM-HIP steels free of exogenous inclusions. The standard M50 steel may be produced by PM-HIP steelmaking with fine carbide microstructures. However, the most attractive aspect of PM-HIP is superior high alloyed HSS bearing steel technologies. Such PM-HIP steels are established based PM-HIP steelmaking and can be applied in demanding applications. Examples of advanced PM-HIP based bearing steels are available under the SAE Aerospace Material Specification AMS 6558 and AMS 6560. The ASEA Stora Process ASP 2055 steel is another example of a PM-HIP HSS applied in rolling bearing component manufacture. Laser additive manufacturing (LAM) requires powders with specific particle sizes and flow properties. The carburizing bearing steel grade M50 NiL has been utilized for rolling bearing ring manufacture with isotropic properties. The ASTM Committee F42 is active in the development of quality assessment methods for metal powders for LAM. State-of-the-art clean-steel PM steelmaking is seen as the future for higher alloyed, high temperature, rolling bearing steel technologies either in the form of wrought or laser-melted layered products.

Author Information

Beswick, John, M.
CEng FIMMM, Montfoort, NL
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Pages: 379–392
DOI: 10.1520/MNL8320200022
ISBN-EB: 978-0-8031-7151-0
ISBN-13: 978-0-8031-7150-3