Atmospheric plasma spray yttria stabilized zirconia - lanthanum zirconate composite coated Inconel -718: High temperature erosive wear studies

High temperature erosion is a critical degradation mechanism influencing the durability of thermal barrier coatings in aerospace and energy applications. The aerospace industry is advancing the development of new TBC materials to improve resistance to high temperature erosion. In this study, atmospheric plasma spray technique (APS) was used to deposit composite TBC on Inconel-718 substrate. Four coating systems, namely 100%YSZ, 100%LZ, 80%YSZ/20%LZ, and 60%YSZ/40%LZ, were applied over a NiCrAlY bond coat. As sprayed coatings were characterized using XRD, FESEM, surface roughness, hardness and porosity to evaluate phase stability and microstructural features. Erosion tests were conducted at 1000°C under impact angles of 30° and 90°. The coatings were evaluated based on mass loss per unit erodent mass. The substrate exhibited the highest erosion rates of 4.581 g/kg at 30° and 4.201g/kg at 90°, due to its lower hardness and absence of a protective microstructure. Among the coatings, YSZ exhibited the lowest erosion rates of 2.038 g/kg (30°) and 2.208 g/kg (90°) due to its dense microstructure and strong inter splat bonding, while LZ exhibited higher erosion rates of 3.135 g/kg (30°) and 3.220 g/kg (90°) due to increased porosity and brittle fracture. The composite coatings showed intermediate performance, with 80%YSZ/20%LZ demonstrating improved resistance (2.261g/kg and 2.423g/kg), whereas 60%YSZ/40%LZ exhibited higher erosion (2.781 and 3.051 g/kg). Failure analysis indicated brittle fracture, splat delamination, and interlamellar delamination as dominant mechanisms. These findings highlight the importance of composite coatings in enhancing erosion resistance of APS deposited TBC.