Influence of rf-power on the plasma carbonitriding of titanium

The present work reports on the effect of input plasma processing power in the range of 350-650W on the microstructure and mechanical properties of plasma nitrided Ti. The plasma processing time was 20 min and a gas mixture of 15% C2H2 and 85% N-2 was used. The characteristics of the carbonitrided layer have been investigated by microhardness measurements, surface roughness measurements, optical microscopy, and X-ray diffraction. The measured surface hardness values of the compound layer shows a maximum of 2050 HV0.1 for the sample treated at a plasma power of 550W. The thickness of the carbonitrided layer continuously increases as the plasma power increases. Moreover, the highest carbonitriding rate of 3.52 mu m(2)/s was observed when the input plasma power was adjusted at 600 W. This high carbonitriding rate of treated titanium samples is ascribed to the high concentration of active carbon and nitrogen species in the plasma atmosphere and the formed microcracks in the near surface of the sample during the plasma processing. (C) 2007 Elsevier B.V. All rights reserved.