Jae Ho Jun

A Study on Composite Coatings of Yttrium Ion-Plating and Pack Aluminizing for High-Temperature Applications

Yttrium (Y) was incorporated by an ion-plating method either before or after pack aluminizing to maximize the corrosion resistance of IN 713C. Various combinations of pack aluminizing and yttrium-ion plating were examined with respect to coating sequence, aluminum activity, and corrosive environment. Of all the various coating combinations examined, the best corrosion resistance was obtained from H/A + Y (high-activity aluminizing + Y-ion plating) type composite coatings. Uniformity of the Y deposition was greatly dependent upon the surface condition of the aluminide-coating layer. The high-activity aluminide coating gave better uniformity of Y deposition than did the low-activity-aluminide coating.Improvement of corrosion resistance by the Y-modified-aluminide composite coatings of H/A + Y type occur because the presence of Y between the Al2O3 columns improves Al2O3 scale adherence and substantially prevents depletion of Al in the aluminide-coating layer.