Hot Corrosion Behaviour of Detonation Gun Sprayed Al 2 O 3 -40TiO 2 Coating on Nickel Based Superalloys at 900°C

Abstract

Hot corrosion is the major degradation mechanism of failure of boiler and gas turbine components. These failures occur because of the usage of wide range of fuels such as, coal and oil at the elevated temperatures. Nickel based superalloys having excellent mechanical strength and creep resistance at elevated temperature are used under such environment but they lack resistance to hot corrosion at high temperature. To overcome these problems hot corrosion resistant coatings are deposited on these materials. In the current investigation Al 2 O 3 -40%TiO 2 powder has been deposited on Superni 718 and AE 435 superalloys by Detonation Gun method. The hot corrosion performance of Al 2 O 3 -40%TiO 2 coated as well as uncoated Superni 718 and AE 435 alloys has been evaluated in aggressive environment Na 2 SO 4 -82%Fe 2 (SO 4 ) 3 under cyclic conditions at an elevated temperature of 900°C. The kinetics of the corrosion is approximated by weight change measurements made after each cycle for total duration of 50 cycles. Scanning electron microscopy was used to characterize the hot corrosion products. The coated samples imparted better hot corrosion resistance than the uncoated ones. The AE 435 superalloy performed better than Superni 718 for hot corrosion in a given environment.