YTTRIUM ACETATE-DERIVED PARTICLE COATINGS FOR MITIGATING OXIDATION AND CORROSION OF INCONEL-625

''Sol paint'' that yields yttrium-based compounds was prepared by mixi ng four chemical ingredients, yttrium acetate tetrahydrate precursor, diethanolamine, isopropyl alcohol, and hydrochloric acid, and then app lied as oxidation/corrosion resistant coatings for Inconel 625 substra tes. Annealing the coatings at 500 degrees C developed a coalescent mi crostructure of coarse particles consisting of amorphous yttrium carbo nate as the major component and crystalline yttrium oxide (Y2O3) as th e minor one. At 700 degrees C, the yttrium carbonate was transformed i nto Y2O3 by decarbonation. Increasing the annealing temperature to 900 degrees C led to the formation of the YCrO3 phase yielded by interact ion between Y2O3 and the Cr2O3 which had arisen from the oxidation of the underlying Inconel; the YCrO3 phase created a particle coating wit h a densified microstructure. There were two key factors in mitigating the degree of oxidation of Inconel at 900 degrees C in air: (1) an up take of oxygen by Y2O3 in the coatings, and (2) a densified coating la yer that suppresses the diffusion and permeation of oxygen through it. Furthermore, inhibiting the rate of NaCl-caused corrosion was not onl y due to the excellent coverage of particle coatings over the entire s urfaces of the substrates, but also may be associated with a good adhe rence of the coatings to the substrates.