The performance of a number of selected diffusion and overlay coatings was evaluated using an atmospheric pressure burner rig; the test environment contained compounds of vanadium, sodium and sulfur. The tests were designed to simulate the deposit chemistry and sulfur trioxide partial pressures expected in a marine gas turbine engine operating on contaminated fuel. The tests were performed for up to 1000 hours at 1300°F and 1650°F. At 1650°F, virtually all the coatings tested were severely corroded, emphasizing the necessity of improved coating materials such as ceramics to resist vanadic corrosion. At 1300°F, FeCrAlY, pack chromide and CoCrAlY coatings with high chromium performed well.
Yttria stabilized zirconia coatings, with selected bond coats, were evaluated with fuels containing low (0.3ppm) and high (21ppm) concentrations of vanadium in atmospheric burner rig at 1650°F. Reaction products, primarily yttrium vanadate, were observed in both tests. The results are discussed in terms of bond coat corrosion and chemistry of the test environment.
