Friction and Wear Behavior of a Cobalt-Based Alloy Implanted with Ti or N
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FRICTION AND WEAR BEHAVIOR OF A COBALT-BASED ALLOY IMPLANTED WITH Ti OR N
S. A. DILLICH,* R. N. BOLSTER AND I. L. SINGER Code 6170, Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375; *National Research Council Research Associate
ABSTRACT Dry sliding friction tests and relative abrasive wear measurements were used to investigate the effects of ion implantation on the tribology of a centrifugally cast Co-CrW-C alloy. Titanium implantation was found to significantly reduce the friction and wear of the alloy. Auger spectroscopy showed that vacuum carburization of the surface occurred during Ti implantation. Similar Ti and C profiles were seen in both carbide and (Co-rich) matrix phases. The abrasive wear resistance of the alloy decreased as a result of N-implantation. Nitrogen implantation did not reduce the friction during dry sliding, however, a change in the wear mode was observed.
INTRODUCTION Cobalt-based superalloys show superior resistance to erosion, abrasion and galling wear owing to their microstructures, which consist of very hard Cr and W carbides dispersed in softer, Co-rich solid solutions [1-4]. Co-Cr-W solid solutions normally have hcp structures at low temperatures. However, in order to insure ductility during practical application, these alloys are designed to have fcc matrices. Because of the technological and strategic importance of superalloy hardface materials, surface treatments to still further improve their mechanical and tribological properties should be investigated. The present study examines the effects of ion implantation on the dry sliding friction and abrasive wear resistance of Stoody 3, a centrifugally cast, cobalt-based alloy (50Co, 31Cr, 12.5W) (51-58 RC). Nitrogen implantation has been reported [5-6] to result in large reductions in wear of many metals and cemented carbides. Similarly, high fluence implantation of Ti has been found to reduce the friction [7], and abrasive [81 and adhesive [9] wear in steels such as AISI 52100, a high carbon chromium steel. Our investigations therefore have concentrated on observing the effects of implantation of these two atomic species. Dry sliding friction tests and relative abrasive wear measurements were made on nonimplanted, Ti-implanted, and N-implanted Stoody 3 disks. Wear tracks on the Stoody 3 surfaces were examined using Scanning Electron Microscopy (SEM) and optical microscopy with Differential Interference Contrast (DIC). The compositions of debris in the wear scars were identified by Energy Dispersive X-ray Analysis (EDX).
EXPERIMENTAL PROCEDURES Friction measurements were made during low speed (0.1 mm/sec) dry sliding, using a ball on flat (disk) test geometry. Tests were conducted in ambient air (30 - 50% RH), at room temperatures, with a normal load of
Mat. Res.Soc. Syrp. Proc. vol. 27 (1984) @sEsevier Science Publishing Co.,
Inc.
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9.8 N. The Stoody disks were tested against a variety of alloy balls which have been described elsewhere [10]. Tests were limited to twenty unidirectional passes of the ball
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