Friction and wear studies in N-implanted Al 2 O 3 , SiC, TiB 2 , and B 4 C ceramics
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R. Kossowsky The Pennsylvania State University, University Park, Pennsylvania 16802
J.-P. Hirvonen University ofHelsinki, Department ofPhysics, Helsinki, Finland
N. Elliott Los Alamos National Laboratory, Materials Science and Technology Division, Los Alamos, NewMexico 87545 (Received 31 May 1988; accepted9 August 1988) Bulk polycrystalline samples of sintered A12O3, and hot-pressed Al2 O 3 , SiC, TiB 2 , and B 4 C ceramics were ion implanted at 77 K with 190 keV N + to a dose of 3 X 1017 N/cm 2 . Nitrogen implantation resulted in reduced friction coefficients for SiC, TiB 2 , and B 4 C samples and a reduction in wear for TiB 2 . Both Al2 O 3 samples showed a significant increase in friction coefficients after nitrogen implantation. Nitrogen-implantation-induced changes in these properties appear to be correlated with the thermodynamic tendency of the sample to form "nitridelike" bonds.
I. INTRODUCTION The effects of ion beams and ion implantation on the structural state and surface properties of metals, semiconductors, and ceramics have been areas of active research for the past several years. A multitude of literature has been published which shows how ion implantation and ion-beam processing techniques can substantially alter the surface of many materials, producing a wide variety of beneficial properties that could not otherwise be obtained.1'2 A large portion of this literature is concerned with the effects of ion implantation on the surface mechanical properties of ceramics. Experiments have clearly shown that changes in the surface mechanical properties can be correlated with the structure and the stress state produced by ion irradiation damage. Page and co-workers examined the effect of implanting 90 keV N 2 into singlecrystal SiC (Ref. 3) and implanting 300 keV Y into single-crystal A12O3 (Ref. 4), both at approximately 525 K. Doses of 4X 1017 N 2 /cm 2 and 3 X 1016 Y/cm 2 in SiC and A1 2 O 3 , respectively, were observed to produce a surface that was amorphous, softer, and had developed compressive stresses. Diamond scratch tests made on the amorphous SiC showed a reduction in wear debris and a decrease in the level of lateral fracture relative to the unimplanted SiC. Similar observations on A12O3 were made by Hioki and co-workers5 who also observed a surface softening and the formation of compressive J. Mater. Res. 3 (6), Nov/Dec 1988
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surface stress following a 300 keV implantation of 2X 1015 Ni/cm 2 at 100 K. McHargue and co-workers6 observed that A12O3 amorphized by either a room-temperature implantation with 175 keV Zr and a dose of 4 X 1016 Zr/cm 2 or a 77 K implantation with 150 keV Cr and a dose of 2X 1015 Cr/cm 2 , possessed a microhardness which was about 60% of that of the crystalline counterpart. Similar observations were made for SiC amorphized at room temperature with 62 keV N and a dose of 1X 1015 N/cm 2 (Ref. 6). Singer7 observed that the hardness of Ti-implanted Si3 N 4 was affected by implantation temperature. Samples presumed to be amorphous after an im
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