Cyclic Oxidation and Hot Corrosion of NiCrY-Coated Disk Superalloy

Powder metallurgy disk superalloys have been designed for higher engine operating temperatures through improvement of their strength and creep resistance. Yet, increasing disk application temperatures to 704 degrees Centigrade and higher could enhance oxidation and activate hot corrosion in harmful environments. Protective coatings could be necessary to mitigate such attack. Cylindrical coated specimens of disk superalloys LSHR and ME3 were subjected to thermal cycling to produce cyclic oxidation in air at a maximum temperature of 760 degrees Centigrade. The effects of substrate roughness and coating thickness on coating integrity after cyclic oxidation were considered. Selected coated samples that had cyclic oxidation were then subjected to accelerated hot corrosion tests. This cyclic oxidation did not impair the coating's resistance to subsequent hot corrosion pitting attack.