Micro and nanostructured alumina-13wt% titania coatings were sprayed via air plasma spraying (APS) technique using nitrogen as primary plasma gas. Microstructural characteristics and mechanical properties of nanostructured coatings are regularly influenced by 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 watched that for nanostructured coatings properties like porosity, micro hardness and percentage of partially melted/ unmelted regions were seen to be monotonic functions of CPSP. However, influence of CPSP on volume fraction of partially melted regions apparently is much smaller in nanostructured Al2O3-13wt%TiO2 coatings deposited using nitrogen as compared to argon as the primary plasma gas. © 2019 Elsevier Ltd. All rights reserved.