SYMPOSIA PAPER Published: 01 January 1993

Cryogenic Turbopump Bearing Material Development Program


Cryogenic rolling element bearings operate in a very hostile environment. Materials used in this environment require a unique combination of characteristics. AISI 440C is the normally selected alloy because of its high chromium content (17%) and resultant corrosion resistance. However, AISI 440C has very poor cryogenic fracture toughness (KIc = 11 MPa√m (10 ksi √in.) at - 267°C (- 450°F) and is prone to stress corrosion cracking (SCC). Alternate materials like AISI 9310 or M50NiL can provide the requisite cryogenic fracture toughness (KIc = 27.5 MPa√m (25 ksi √in.) at - 267°C (-450°F) and SCC resistance, but neither provide general corrosion resistance due to their low chromium content.

In 1988, MRC Bearings and Pratt and Whitney (P&W) initiated a combined research and development program aimed at developing a cryogenic corrosion resistant, fracture tough bearing steel. The approach was to case harden by carburization a fracture tough class 3 super 12 stainless steel. This paper discusses the successful carburization process developed by MRC and P&W on an experimental carburizing stainless steel bearing alloy developed by Carpenter Technology, designated EX98. Finally, data derived on the resultant material properties will also be discussed.

Author Information

Spitzer, RF
Materials Engineering, MRC Bearings, SKF Aerospace, Jamestown, NY
Chin, HA
Component Design and Technology, Pratt & Whitney, West Palm Beach, FL
Haluck, DA
Component Design and Technology, Pratt & Whitney, West Palm Beach, FL
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Developed by Committee: A01
Pages: 156–167
DOI: 10.1520/STP24832S
ISBN-EB: 978-0-8031-5246-5
ISBN-13: 978-0-8031-1850-8