Nitretação a plasma de zircônia parcialmente estabilizada

Abstract

High temperature plasma nitriding of yttria-partially stabilized zirconia in atmospheric pressure microwave plasma was investigated. The morphological, mechanical and physico-chemical characteristics of the resulting nitrided layer were characterized by different methods, like optical and scanning electron microscopy, micro-indentation, X-ray diffraction, narrow resonant nuclear reaction profiling, secondary neutral mass spectrometry, and X-ray photoelectron spectroscopy, aiming at investigating the applicability of this highly efficient process for nitriding of ceramics. The structure of the plasma nitrided layer was found to be complex, composed of tetragonal and cubic zirconia, as well as zirconium nitride and oxynitride. The growth rate of the nitrided layer, ~ 4 μm min-1, is much higher than that obtained by any other previous nitriding process, whereas a typical 50% increase in Vickers hardness over that of yttria-partially stabilized zirconia was observed. The adherence of the nitrided layer to the zirconia substrate is assured by the fact that the ZrN layer grows from the substrate through a thermally activated mechanism whereby N atoms replace O atoms in the zirconia network.