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Item A microstructural study and high-temperature oxidation behaviour of plasma sprayed NiCrAlY based composite coatings(Elsevier B.V., 2025) Hebbale, A.M.; Ramesh, M.R.; Petr?, J.; Chandramouli, T.V.; Srinath, M.S.; Shetty, R.K.In this study, the development and performance evaluation of plasma sprayed NiCrAlY based coatings, such as NiCrAlY, NiCrAlY + Al?O? and NiCrAlY + YSZ on T91 steel substrates for high temperature applications is carried out. Microstructural features, phase composition and oxidation resistance under cyclic oxidation at 800 °C of the coatings were characterized. Analysis of the XRD confirmed the formation of protective phases such as Cr?O?, Ni?Al and NiAl, and the improvement observed in the coating's performance was due to the addition of Al?O? and YSZ. Oxidation resistance was improved for the NiCrAlY + Al?O? coating through the formation of a dense Al?O? oxide layer, but the NiCrAlY + YSZ coating was superior in terms of thermal stability and spallation resistance, because YSZ has low thermal conductivity and high thermal shock resistance. Composite coatings showed improved cyclic oxidation behavior and microstructural analysis revealed reduced porosity and enhanced integrity. The results demonstrate that the addition of Al?O? and YSZ in the NiCrAlY coatings leads to capability of tailoring NiCrAlY–based coatings for high temperature industrial applications with improved durability and oxidation protection. © 2025 The Author(s)Item Studies on high-temperature erosion behaviour of HVOF sprayed NiCr based composite coatings(Elsevier B.V., 2025) Medabalimi, S.; Hebbale, A.M.; Gudala, S.; Ramesh, M.R.; Gujar, R.; Aravindan, N.; Petr?, J.Solid particle erosion at high temperature is a major problem in many industries and advanced protective coatings are needed to extend the service life of components subjected to harsh environment. The main objective of this study is to investigate the erosion behavior of HVOF sprayed (NiCr) + 5 % Si and (NiCr)+ 2% C based composite coatings at different impact angles and temperature, with specific emphasis on the effect of coating composition. The coatings exhibited excellent erosive wear resistance at elevated temperatures due to the formation of stable oxide layers (CrO, NiCr?O?, SiO?) and the incorporation of silicide phases (Ni?Si) to the NiCrSi coatings. However, NiCrC coatings containing hard carbide phases (such as NiC) showed higher erosion resistance at higher temperatures and normal impact angles (90°) because of their robust microstructure and thermal stability. The analysis of microhardness indicated that NiCrSi coatings provided higher hardness attributable to silicides and were therefore better suited to moderate erosive environments, whereas NiCrC coatings, with slightly lower hardness, exhibited excellent resilience under severe erosive environments. SEM, EDAX and XRD analyses showed that preferential erosion mechanisms were cutting and plowing at oblique angles (30°) and brittle fracture at normal angles (90°). Notably, at 800 °C, NiCrC coatings outperformed the NiCrSi coatings via consistently superior thermal and erosion resistance. These findings indicate that HVOF sprayed NiCrC coatings are suitable for high temperature erosion protection, and NiCrSi coatings are specifically developed for high erosive wear resistance at low impact angles. © 2025 The Author(s)