Friction, Wear and Deformation of Soft Steels Implanted with Ti and N
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FRICTION,
WEAR AND DEFORMATION OF SOFT STEELS IMPLANTED WITH TI AND N
I.L. SINGER,* AND R.A. JEFFRIES"' *Naval Research Laboratory, Code 6170, Chemistry Division, Washington, DC 20375, **Geo-Centers, Inc., 4710 Auth Place Suitland, MD 20746
ABSTRACT Friction and wear measurements were performed with a hardened steel ball sliding against unharlened s$eels (AISI+ 10184 304 and M2) implanted with either N or Ti or both N + Ti ions. Dry and lubricated sliding studies found that: Ti-implantation reduced friction and thereby delayed wear; N-implantation did not reduce friction but delayed wear by increasing th$ resistance of the surface to shear; and dual implants of N + Ti showed effects of both implants. Auger sputter depth profiles found the 1018 and M2 surfaces enriched in implanted N and bulk C. No evidence of N migration could be found in heavily deformed surfaces.
INTRODUCTION Ti and N implantations have been shown to affect both the wear rate and the friction behavior of steels, but in different ways. Ti-implantation has been found effective at high fluences in reducing friction and wear in a variety of steels of different microstructures (e.g. ferritic, martensitic, austenitic, precipitation hardened) [1-6]. N-implantation has been found to reduce wear in all but through hardened steels, but not to reduce friction [1.6-8]. These studies suggest that during sliding contact Ti-implantation reduces adhesion whereas N increases the surface's resistance to deformation. Similar effects for Ti and N implants have also been found on a Co-based carbide alloy [10,11]. The present study was designed to investigate the effects of implanting both N and Ti on the friction and wear behavior of the three unhardened steels listed in Table I. First, N ions were implanted deep, then Ti ions shallow so that the effects of the two implant species might be separate. Ti ions were implanted to a fluence capable of producing a low friction surface on f hardened bearing steel [9]. Implantation parameters for N and Ti ions are listed in Table II. Friction and wear measurements were performed on nonimplanted, N-, Ti-, and dual (N + Ti) implanted steels with a hardened steel ball slider under dry and lubricated sliding conditions (Hertzian stress = 0.85 GPa). Wear tracks were analyzed by optical and scanning electron microscopes, and surface compositions were determined by Auger analysis. TABLE I. Steel Type (AISI)
304 1018 M2
Composition,
microstructure and hardness of steel disks.
Composition (at.%)
Fe 20Cr-8Ni Fe-IC Fe-4.4Cr-3.OMo-2.3V 1.9W-4.1C
Mat. Res. soc. Syimp. Proc. Vol.
Microstructure
Knoop Hardness (20N load; in GPa)
Austenite Ferrite and Cementite Ferrite and Alloy Carbides
27 (1984)QElsevier Science Publishing Co., Inc.
2.9 2.6 2.5
668
TABLE II. Implanted Ion N + Ti
Implantation parameters for N and Ti ions. Fluence 17 2 (10 /cm ) 4 2
Energy (keV)
Range (nm)
180 50
190 18
EXPERIMENTAL All steel samples were cut from as received bar stock, then were polished to a metallographic finish. The ion implanter
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