Hot corrosion studies on as-received and HVOF sprayed Al2O 3+CoCrAlTaY on Ti-31 alloy in salt environment

Abstract

The present investigation is on the High Velocity Oxy-Fuel coating of Ti-31 alloy using fused, blended powder, Al<inf>2</inf>O<inf>3</inf>+CoCrAlTaY. Hot corrosion experiments were done on the coated and uncoated Ti-31 under a salt environment of 50% Na<inf>2</inf>SO<inf>4</inf> and 50%V<inf>2</inf>O <inf>5</inf> at 800°C. Thermogravimetric cycles of 1 hour heating and 20 minute cooling was followed for hot corrosion study. After each cycle weight measurement was carried out. After hot corrosion, the samples were characterized using XRD and SEM/EDS. It was observed that the coated sample is more resistant to hot corrosion than uncoated sample. XRD and SEM analysis indicated that the surface is rich in oxides. Gravimetric analysis indicated that the sample weight gain was following a parabolic relationship with time. A damage mechanism is discussed for the hot corrosion damage of the samples. Presence of high level of chromium in HVOF sprayed coating imparts improved hot corrosion resistance at 800°C, in a molten salt environment of Na<inf>2</inf>SO<inf>4</inf> + V <inf>2</inf>O<inf>5</inf>. © 2013 The Authors. Published by Elsevier Ltd.