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A systematic investigation was undertaken on commercially pure titanium submitted to plasma nitriding. Thirteen different sets of operational parameters (nitriding time, sample temperature and plasma atmosphere) were used. Surface analyses were performed using X-ray diffraction, nuclear reaction and scanning electron microscopy. Wear tests were done with stainless steel Gracey scaler, sonic apparatus and pin-on-disc machine. The obtained results indicate that the tribological performance can be improved for samples treated with the following conditions: nitriding time of 3 h; plasma atmosphere consisting of 80%N 2 +20%H 2 or 20%N 2 +80%H 2 ; sample temperature during nitriding of 600 or 800 °C.

Wear potential may be related to the coefficient of friction in Noritake ceramics, which had a lower coefficient than Eris ceramics. Within-group analysis showed no differences in polished or glazed specimens. The differences observed were not associated with microhardness.

Near-surface composition and tribological behaviour of plasma nitrided commercially pure (CP) Ti have been investigated using x-ray diffraction, nuclear reaction analysis, scanning electron microscopy, wear assays with stainless steel Gracey scaler and sonic apparatus, and friction coefficient measurements. The total wear behaviour can be divided into two steps. The first step is the growth of an oxynitride layer. The second step is the breakdown of the oxynitride layer during which debris is produced, increasing the friction coefficient. Each sample exhibits features that correlate with the near-surface composition. For instance, the presence of thin layers of ε-Ti 2 N and δ-TiN precipitating on the near-surface region control the transition from the first to the second step.

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