SYMPOSIA PAPER Published: 08 September 2020

Improved Processing Techniques for Inclusion-Free Steel for Bearing and Mechanical Component Applications


High-hardness, high-carbide powder metallurgy tool steels such as M62 enable the use of ball bearings at extremely high load and stress levels increasing the potential for rolling contact fatigue failure attributed to nonmetallic inclusions. Ever-cleaner steels are sought, but the results have been uneven, owing to the random nature of the occurrence of such material flaws. Careful melting processes and thorough ingot inspections prior to bearing manufacture are common approaches to avoid inclusions. Selecting only the cleanest portions of an ingot may result in bearings relatively free from material flaws. This approach is not always successful because detrimental flaws that exist deep within an ingot can pass inspections undetected, potentially causing subsequent failure. Recent efforts to commercialize an intermetallic material, 60NiTi, for rolling element bearings demonstrates a pathway to produce bearing steel that is free from unwanted ceramic particle inclusions. In this paper, the process used to make bearing-grade, inclusion-free NiTi alloys is described and applied to steelmaking. At its core, the NiTi process differs from steelmaking in one key aspect. NiTi alloys are made from elementally pure starting materials that are melted, blended, and processed in equipment that minimizes exposure to oxygen and other sources of contamination, ensuring an inclusion-free product. In contrast, the predominant method to make bearing steel is to employ a successive series of melt purification steps to reduce contamination levels below required thresholds. This paper describes the processes developed and applied to high-carbide tool steel, M62. The resulting material and microstructures are evaluated and compared to M62 prepared by conventional powder production and consolidation techniques. It is hoped that the application of materials manufacturing techniques used for fracture-sensitive ceramics and intermetallic materials such as NiTi can provide a pathway to nonmetallic inclusion-free steels for rolling element bearings and other failure critical applications.

Author Information

DellaCorte, Christopher
NASA Glenn Research Center, Cleveland, OH, US
Price: $25.00
Contact Sales
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Pages: 313–331
DOI: 10.1520/STP162320190042
ISBN-EB: 978-0-8031-7693-5
ISBN-13: 978-0-8031-7692-8