Investigation of thermally sprayed NiCrAlY/TiO2 and NiCrAlY/Cr2O3/YSZ cermet composite coatings on titanium alloys

Abstract The present work investigates the hot corrosion behavior of thermally sprayed 65 pct NiCrAlY + 35 pct TiO 2 and 65 pct NiCrAlY + 30 pct Cr 2 O 3 + 5 pct YSZ coatings on titanium 15 alloys. The coatings on the titanium 15 alloy substrates exhibit a near-uniform, dense, and adherent microstructure with a porosity of 2.7 to 2.9%. Thermogravimetric studies are made to examine the hot corrosion performance of coatings in a molten salt environment of Na 2 SO 4 + 60%V 2 O 5 at the temperature of 700 °C for 50 cycles. One cycle is carried out by heating for a period of one hour and cooling the sample at ambient conditions. The corrosion products are analyzed based on scanning electron microscopy, energy dispersive analysis, and X-ray diffraction techniques to study the morphology, phase composition, and abundance of the high-temperature corrosion constituents. The bare titanium-15 alloy, 65 pct NiCrAlY + 35 pct TiO 2 coating and 65 pct NiCrAlY + 35 pct Cr 2 O 3 + 5 pct YSZ coating produced a weight gain of 307.92 mg cm −2 , 42.16 mg cm −2 and 44.02 mg cm −2 respectively after the period of 50 cycles. The effective resistance of the coatings is due to the formation of Ni 3 V 2 O 8 , NiCr 2 O 4 , Cr 2 O 3 & AlV 2 O 4 phases.