Microstructural and mechanical characterization of plasma sprayed Al2O3–TiO2 composite ceramic coating on Mo/cast iron substrates

The principle aim of this paper is to investigate the performance of protective multilayer coatings with Al2O3–TiO2/Mo/cast iron architecture in order to use in internal combustion engines. With this regard, alumina–titania composite powders were deposited on Mo coated cast iron substrates using an atmospheric plasma spray system. The coated samples were characterized by means of optical microscopy, image analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical properties of the multilayers were determined by a combination of three-point bending test, Vickers and Knoop microhardness measurements, before and after oxidation at 600 °C for 16 h. The microstructural observations showed that the multilayers contain some inhomogeneities such as porosity, crack-like defects, unmelted particles, oxides and inclusions.