Two nominally 200-hour tests were conducted in the General Electric Company’s Pressurized Fluidized Bed (PFB) Coal Combustion facility in Malta, NY. The purpose of the tests was to evaluate the influence of bed operating temperature and dolomite composition on the degradation of gas turbine vane and blade base alloys and protective coating/cladding systems in the effluent from a PFB. Operating conditions were as follows: 1) 1710°-1770°F (932°C-966°C) bed temperature and Pfizer dolomite (0.1 wt% sodium plus potassium), and 2) 1630°-1690°F (888°-921°C) bed temperature and Tymochtee dolomite (0.9 wt% sodium plus potassium). Brookville seam coal with 4.5 wt% sulfur, 0.3 wt% alkali, and 0.17 wt% chlorine was used in both tests.
Bare nickel and cobalt-base vane and blade alloys were susceptible to hot corrosion over the entire temperature range investigated, 1100°-1600°F (593°-871°C). CoCrAlY and FeCrAlY overlay coatings showed good corrosion resistance at temperatures above 1450°F, but were susceptible to pitting attack at lower temperatures. A platinum-aluminide diffusion coating showed excellent corrosion resistance at all temperatures.