MODIFICATION OF TRIBOMECHANICAL PROPERTIES OF COMMERCIAL TIN COATINGSBY CARBON ION-IMPLANTATION

Physical vapour deposited commercial TiN coatings of about 2 mu m thic kness on high speed steel substrates were implanted at room temperatur e with 95 keV carbon ions at nominal doses between 1 x 10(17) and 8 x 10(17) ions cm(-2). An ultra-microhardness apparatus (UMIS-2000) was u sed to measure hardness, and a pin-on-disc machine (CSEM tribometer) w ith a sapphire ball was used to measure wear, friction and adhesion. C arbon implantation induced a significant improvement in ultra-microhar dnesss friction coefficient and wear properties. The surface microhard ness increases monotonically by up to 115% until a critical dose phi(c rit) is reached. Beyond this dose the hardness decreases, but remains higher than that of unimplanted sample. A lower friction coefficient a nd a longer transition period towards a steady state condition were ob tained by implantation. Proton elastic scattering (PES) measurements s how loss of nitrogen after implantation by up to 27%. Rutherford backs cattering (RBS) analysis indicated that some implanted carbon has diff used out from the implanted region towards the TiN surface. The change s in tribomechanical properties are discussed in terms of radiation da mage and possible second phase formation.