Investigation of thermally sprayed NiCrAlY/TiO <sub>2</sub> and NiCrAlY/Cr <sub>2</sub> O <sub>3</sub> /YSZ cermet composite coatings on titanium alloys
G. Madhu Sudana Reddy, C. Durga Prasad, Pradeep Patil, Gagan Shetty, М. Р. Рамеш, Tingke Rao
Abstract
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.