Effects of gas pressure and bias potential on electron beam nitriding of titanium

We have studied the effects of gas pressure and bias potential on ion-plasma nitriding of titanium in an electron beam-produced plasma generated in the forevacuum pressure range. We present the results of scanning electron microscopy, x-ray analysis, and tribological studies of the modified layers of nitrided samples. The results of measurements are given, and the correlation between parameters (ion mass-to-charge composition, plasma density, electron temperature) of the beam-plasma and of the nitrided surface is found. Increased working gas pressure leads to an increase in the fraction of atomic nitrogen ions in the plasma, which results in increased surface layer hardness, depth of penetration of nitrogen atoms into the sample, and wear resistance. Higher absolute values of sample bias potential contribute to increased plasma density near the sample surface and a corresponding increase of hardness and wear resistance of the sample.