Fused silicon-rich coatings for superalloys

Various compositions of nickel-silicon and aluminum-silicon slurries were sprayed on IN 100 specimens and fusion-sintered to form fully dense coatings. Cyclic furnace oxidation tests in 1 atm air at 1100 C showed all the coatings to be protective for at least 600 hours, and one slurry, Al-60Si, was protective for 1000 hours. This coating also protected NASA TAZ 8A and NASA-TRW VIA for 1000 hours in the same furnace test. Alloys B 1900, TD-NiCr, and Mar-M200 were protected for lesser times, while NX 188 and NASA WAZ 20 were scarcely protected at all. Limited stress-rupture testing on 0.64-cm-diam IN 100 specimens detected no degradation of mechanical properties due to silicon diffusion.