Methane Plasma Source Ion Implanted Ti-6Al-4V
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METHANE PLASMA SOURCE ION IMPLANTED Ti-6Al-4V Jie Chen, J.R.Conrad, R.A.Dodd, F.J.Worzala University of Wisconsin-Madison, Plasma Source Ion Implantation Program, Madison, WI 53706 ABSTRACT coupons were ion implanted using Ti-6A1-4V alloy test methane Plasma Source Ion Implanter at an energy of 30 KeV. Multi-energy ion implantation, carbon film deposition as well as The resulted ion beam mixing were involved in this process. carbon profile is flat-top near the surface which forms a TiC The implanted layer has demonstrated high load capacity layer. condition. time under pin on disk wear test and long life INTRODUCTION Ti alloys are a group of materials known for their poor wear resistance. Ion implantation has been proved to be a successful Nitrogen, carbon way of improving their tribological properties. The most effective and boron are commonly used species [1-4]. ion for improving the wear properties seems to be N, and the best results are achieved at highest doses where nearly continuous Ti alloys implanted with carbon layers of TiN are formed [5]. ions are reported to have lower load capacity and shorter life time (2]. Good results are found only when implanted with carbon and heat treated to increase carbide size (1]. The present work reports the structure and properties of Ti6AI-4V alloy implanted with carbon using a Plasma Source Ion Implanter (PSII) with a methane plasma. With PSII, the substrate is placed directly in the plasma source, resulting in a costeffective technique for ion implantation in non-semiconductor applications [6,7]. EXPERIMENTAL PROCEDURE Samples of mill-annealed Ti-6AI-4V alloy were used, all specimens being originally mechanically polished with 1 gm diamond paste. Ion implantation was performed in a Plasma Source Ion Implanter, and detailed descriptions of this implanter have Samples were sputter-cleaned by been presented elsewhere (8,9]. Ar ions before implantation for 20 minutes, following which a methane plasma was generated in the implantation chamber with the 4 Samples were pulse biased to -30 pressure kept at 4x10 Torr. The source plasma ion species mix, which KV during implantation. Upon was not measured, is assumed to be dominated by CH 4÷ ions. impact, each 30 KeV CH 4÷ ion breaks up into a 22.5 KeV C ion and The implanted dose was estimated four H ions17 with 2.52 KeV each. to be 3x10 ions/cm . The carbon depth profile was measured by a Scanning Auger while chemical bonding and structure electron microscopy, information of the implanted layer were obtained by ESCA and TEM. electropolishing from the TEM samples were prepared by unimplanted side. Mat. Res. Soc. Symp. Proc. Vol. 190. @1991 Materials Research Society
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Microhardness was measured by a Knoop hardness tester. The wear test used was a pin on disc test, the pin being 3mm diameter ruby ball. The rotation speed of the disc was adjusted to be 12 mm/s, and WD-40 was used as a lubricant. The depth of the wear track was measured by an alpha-step profilometer. RESULTS Auger Depth Profile The Auger depth profile of implant
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