Conventional and nanostructured yttria stabilized zirconia coatings were deposited by air plasma spraying (APS) technique using nitrogen as the primary plasma gas. Microstructural characteristics and mechanical properties of nanostructured coatings are typically affected by the percentage of unmelted/partially melted regions. Hence, the coatings were obtained as a function of critical plasma spray parameter (CPSP) defined as the ratio of arc power to the primary plasma gas flow rate. It was observed that for nanostructured coatings properties like porosity, microhardness and percentage of partially melted/ unmelted regions were seen to be monotonic functions of CPSP. However, the influence of CPSP on the volume fraction of partially melted regions is seen to be much smaller in nanostructured yttria stabilized zirconia coatings deposited using nitrogen as compared to argon as the primary plasma gas.

Keywords: Air plasma spraying, Nanostructured coatings, CPSP, Yttria stabilized zirconia.