Methane and nitrogen plasma immersion ion implantation of titanium metal

Abstract

Plasma immersion ion implantation (PIII) is employed to enhance the tribological properties of titanium. The effectiveness of methane PIII and glow discharge nitrogen PIII, as well as radio-frequency (RF) nitrogen PIII, is compared by measuring the microhardness, mass loss due to wear and the coefficient of friction of samples treated by the three methods. Nitrogen PIII is a hybrid surface treatment technique combining nitrogen-ion implantation, which occurs during the high-voltage pulses, and plasma nitriding, which takes place in between pulses. Our experimental data show that the surface properties of titanium are enhanced by all three treatment processes, but nitrogen PIII yields better results than methane PIII, and RF nitrogen PIII is the best treatment process of the three. On the basis of our Auger depth profiling results, the discrepancy appears to be related to the larger penetration depth (implantation plus radiation-enhanced diffusion) of nitrogen by the RF PIII process. The slight difference between methane PIII and glow discharge nitrogen PIII samples appears to arise from the absolute implanted dose.