Bimodal distribution characteristic of microstructure and mechanical properties of nanostructured composite ceramic coatings prepared by supersonic plasma spraying

Nanostructured composite ceramic coatings (NCs) were deposited by supersonic plasma spraying (SPS) technique. The microstructures of NCs were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The results showed that the microstructure of NCs exhibited a bimodal distribution consisting of fully melted regions (FM regions) and partially melted regions (PM regions). With the spray power increasing, the proportions of FM regions and PM regions both increased, but no distinct laws were found. The measured data of elastic modulus, micro-hardness and fracture toughness were analyzed using Weibull statistics. The results showed that these micromechanical properties followed Weibull distribution and presented a characteristic of bimodal distribution. (C) 2014 Elsevier Ltd. All rights reserved.