Vapor-deposited emittance-catalysis coatings for superalloys in heat-shield applications

Results are presented for dynamic oxidation tests of Inconel 617 and MA956 superalloy specimens prepared with aluminosilicate coatings formulated to have a high emittance and a low catalytic activity. Results indicate that coated MA956 has a much lower catalytic activity after 5.5 h (19 cycles to temperature) of exposure at temperatures near 1370K than does uncoated MA956. The net effect of emittance-catalysis enhancement coatings on MA956 is a 100% increase in the energy input required to produce a surface temperature of 1370K. The net effect of the coating on Inconel 617 is a 50% increase in the energy input required to produce the same surface temperature. This lesser effect for Inconel 617 results from interaction between the coating and the oxides of the Inconel 617 alloy. 12 ref.--AA