Surface mechanical properties of C implanted Ni
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J.-P. Hirvonen Department of Physics, University ofHelsinki, Helsinki, Finland
T. R. Jervis Los Alamos National Laboratory, Materials Science and Technology Division, Los Alamos, New Mexico 87545
G.M. Pharr Department ofMaterials Science, Rice University, Houston, Texas 77251
W.C. Oliver Metals and Ceramic Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (Received 12 August 1987; accepted 16 December 1987)
Nickel foils, 165/mi thick, have been carbon implanted at 300 K with 2,3, and 4.2 X 1017 Cions/ cm2 and implanted with a two-step implantation of 2.1X 1017 C/cm 2 at 300 K followed by 2.1X 1017 C/cm 2 at 77 K. All implantations performed at 300 K result in the formation of the metastable phase Ni3C while the two-step implantation produces an amorphous Ni/C alloy. Surface mechanical property studies showed that both the surface hardness and wear properties are correlated with chemistry (carbon dose), and that the friction coefficient is additionally dependent on the surface microstructure. It was found that both the wear rate and coefficient of friction were reduced as the volume fracion of Ni 3 C increased. At the highest dose implanted, 4.2 X 1017 C/cm 2 , the coefficient of friction was found to be lower for the sample implanted half at 300 K and half at 77 K and possessing an amorphous structure compared to the sample implanted entirely at 300 K and possessing a crystalline Ni3C structure. Increases in the surface hardness were also observed with increasing carbon content, with the greatest hardness observed in samples implanted to a total dose of 4.2 X 1017 C/cm 2 . The hardness at this dose was not dependent on the implant conditions or the metastable phase formed.
I. INTRODUCTION Ion-beam technology has been very effective in the production of unique and novel materials.' In particular, ion implantation is exceptionally well suited for metastable phase synthesis.2 Unlike ion-beam mixing where alloying is dependent on favorable mixing thermodynamics,3 ion implantation can introduce nearly any element into the surface of any solid, greatly expanding the possible number of new and interesting metastable alloy systems. On the practical side, many of the novel metastable phases formed by ion implantation possess improved tribological and mechanial properties.4"6 For example, the implantation of carbon and titanium into iron produces an amorphous phase with improved wear and friction properties7; similar effects have also been observed in steels implanted with Ti or C 8~'° and NiTi implanted with N . ' ' In addition, surface hardness can also be increased as has been observed in high-dose boron or phosphorus-implanted nickel.12 In the present paper we explore the effect of carbon implantation on the surface mechanical properties of 226
J. Mater. Res. 3 (2), Mar/Apr 1988
http://journals.cambridge.org
nickel. Specifically we will examine the wear and friction properties and surface hardness of nickel as a function of carbon implantation and Ni-C phase formation. II. EXPERIMENTAL Foil samp
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