Effects of plasma process parameters on wear properties of zirconia coatings

Abstract

This paper reviews plasma deposition method of zirconia based ceramic coatings with regard to tribological applications. Subjects discussed include wear-resistant coatings from yttria-stabilized zirconia (YSZ) processed by plasma-spray technique on the stainless steel substrates employing non-equilibrium plasma spray technology at atmospheric pressure. Titanium steel is widely used for metallic prosthesis of artificial joints. Yttria stabilized zirconia (5 wt% yttria), distinguished for inertness, good biocompatibility with human tissues, good mechanical and tribological properties, is chosen for investigations. The thickness of plasma deposited coatings is 30-60 μm. The microstructure, surface morphology and phase analysis of the tested samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The microhardness of sprayed samples was evaluated by Vickers technique. Surface roughness was characterized by means of selected roughness parameters. The relation between process parameters, microstructure, surface texture and wear properties of as-sprayed coatings was investigated. It was found that the coatings formed by plasma spray technology are nanocrystalline with tetragonal crystal structure. Deposition temperature in the analyzed interval of 2200- 3500 oC does not have significant impact on the crystal structure of sprayed samples. Temperature only insignificantly influences the crystallites size of investigated coatings. Coatings formed at higher temperature are characterized by more dense fine grain structure. Zirconia coatings are well adhered to the covering surfaces. The analysis of the microhardness measurements resulted that coatings formed at higher temperature are characterized by higher microhardness values. The variation of main surface roughness parameters Rz and Ra subjected to process parameters is presented.