(November 1st, 2010)
At Pacamor Kubar Bearings (PKB), we manufacture the vast majority of our miniature and instrument ball bearing rings from AISI 440C stainless steel, which is the standard material for most domestically manufactured miniature and instrument bearings for aerospace and medical applications. We also provide specially heat treated 440C for cryogenic applications or other extreme environments and occasionally manufacture ball bearings from other specialty steels.
There are some cases where customers ask for AISI 52100, a steel used in the bearing industry for many years but, in most cases has been replaced by 440C on newer drawing revisions and in new applications. The purpose of this blog is to offer some information about 440C as compared to 52100, particularly in corrosive environments.
According to “A Comparison of the Performance of AISI 52100 and AISI 440C Ball Bearings in a Corrosive Environment” Squires & Radcliffe, Central Energy Generating Board (CEGB-UK) Scientific Services & CEGB Berkeley Nuclear Laboratories, the results show that 440C stainless steel resists corrosions twice as well as conventional 52100 steel.
CEGB performed tests on 150 bearings made from En31 (AISI 52100) and AISI 440C materials and published their results in the Journal of Materials Science. “The clear conclusions were that the stainless steel bearings performed twice as well as the standard En31 bearings in terms of fatigue life, as well as being far superior both for corrosion resistance and for unlubricated running.”
CEGB’s experiments compared the performance of AISI 52100 ball bearing steel and AISI 440C stainless steel. The bearings made from AISI 52100 had been suffering from corrosion damage in the application. The test atmosphere was moist carbon dioxide at a pressure of about 3 MPa, and bearings were deliberately contaminated with a representative amount of sodium chloride. The objective of the tests was to compare the rolling-contact fatigue performance of the materials and to look for other failure mechanisms in the ball bearings. Failure rates were found to be between 1 and 2 times more than would have been expected under ideal conditions. The failure mechanism was primarily identified as rolling contact fatigue. Results were analyzed statistically by assuming that failures fitted an exponential distribution, and it was shown that the stainless bearings performed more than twice as well as those made from conventional steels.
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