The effect of spray angle on the microstructural and mechanical properties of plasma sprayed8YSZ thermal barrier coatings

Abstract

Thermal barrier coatings (TBCs) are favorable for better protection of gas turbines and aero engines at high temperatures. The TBCs were fabricated using NiCrAlY bond coat and 8% wt. yttria-stabilized zirconia (YSZ) topcoat onto the nickel-based superalloy Inconel 800 by atmospheric plasma spray. In this article, the investigation of microstructural and mechanical properties of 8YSZ TBCs with the effect of spray angle has been discussed. The microstructural and elemental analyses were conducted by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). The porosity analysis was conducted based on SEM image analysis using a gray scale threshold. Mechanical properties such as coating hardness, surface roughness, and thickness are measured by indentation, surface profilometer, and optical microscopy. The result shows the effect of the spray angle over the coating surface in terms of pores and microcracks. The influence of the spray angle leads to different grain growth resulting in the shadow region. A large number of defects and a decrease in coating hardness were observed for 60 degrees pray angle compared to the 90 degrees pray angle. A large number of defects led to developing rough surfaces, resulting in low hardness and increased porosity. The experimental results showed that the plasma sprayed 8YSZ TBC with a 90 degree spray angle can improve the durability and performance of the TBCs, as it has better microstructural and mechanical properties.