Effects of Ion Implantation on the Rolling Contact Fatigue of 440C Stainless Steel
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EFFECTS OF ION STAINLESS STEEL
IMPLANTATION
ON
THE
ROLLING
F. M. KUSTAS,* M. S. MISRA,* AND P. SIOSHANSI** *Martin Marietta Denver Aerospace, P.O. Box 179, Corporation, Patriots Park, Bedford, MA 01730
CONTACT
FATIGUE
OF
440C
Denver CO 80201; **Spire
ABSTRACT Cylindrical 440C stainless steel specimens implanted with N and Ti were examined for their fatigue resistance and wear behavior by rolling contact fatigue (RCF) testing. The results obtained from RCF testing showed a 40% increase in the B-10 fatigue lifetime for N implanted and a 17% increase for Ti implanted 440C specimens compared to baseline, unimplanted 440C. Quantitative surface analysis by Auger Electron Spectroscopy (AES) was performed to determine the effects of process parameter optimization and ion beam masking on the elemental concentration profiles.
INTRODUCTION Corrosion resistant stainless steels, such as 440C, are currently used for many aerospace bearing applications where good corrosion resistance and high load carrying capacity are primary requirements. Even though 440C steel exhibits excellent corrosion resistance it suffers from a low fatigue and wear resistance, especially in high load/high RPM applications. Premature failure of critical bearing components, before the useful design lifetime, has resulted in a reduced reliability of aerospace systems. Increasing the fatigue resistance of 440C stainless steel bearing components by 50-100% would have a significant impact on the operating efficiency of Space Transportation Systems. Conventional surface treatments suffer from inadequate coating adhesion, and processing restrictions such as high temperature application and final grinding for dimensional accuracy. A novel surface processing technique which avoids all of the conventional coating deficiencies is ion implantation. This technique is useful for modifying surface dependent properties and its inherent advantages include, formation of highly alloyed, amorphous surface layers with no definable interface. It has been established that ion implantation can provide wear and cyclic fatigue resistant surfaces by careful selection of processing parameters [1-31. For example, Ti implantation of 52100 and 440C steels has shown a reduction in the kinetic coefficient of friction by up to 39% for 52100 [1) and 63% for 440C [2] steels. For the more severe condition of cyclic fatigue, an improvement in the fatigue endurance life of 1018 steel has been observed for N implantation followed by an annealing heat treatment [3]. Therefore ion implantation with Ti, for modification of the coefficient of friction, and N, for intermetallic compound formation, was selected as an approach to improve the rolling contact fatigue resistance of 440C steel.
Mat. Res.
Soc. Syrp. Proc. Vol. 27 (1984) @.Eleevier Science Publishing Co.,
Inc.
686
EXPERIMENTAL Test Specimens Cylindrical 0.375 in. diameter by 3.25 in. long rods, fabricated from 440C stainless steel (18 wt% Cr, 1.02 wt% C, 0.56 wt% Mo), were used for the rolling contact fatigue (RCF) testing
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