Effect of Aluminum Content in Pack Cementation Mixture on Microstructure and Cyclic Oxidation Performance of Zr-modified Aluminide Coatings

A suitable bond coat to control the spallation is recommended for increasing service life of the coatings. Using modified aluminide coatings as a bound coat has become a common approach nowadays. In this work, a zirconium modified nickel aluminide coating was formed by pack cementation process and the effect of the percentage of aluminum in Al-Cr alloy, which was used as the source of aluminum in coating process, was studied. ZrOCl2.8H2O and alumina were also used as activator and filler material, respectively. Cyclic high-temperature oxidation test was carried out at 1100 °C. Each cycle was consisted of one hour heating in furnace and 10 minutes cooling in the air. Microstructures of the coatings were investigated by means of SEM. EDS analyses were carried out to specify chemical composition of different layers of the coating. Phase analysis was examined by XRD. The results confirmed that the coatings produced by high activity of aluminum source, showed higher resistance to cyclic high-temperature oxidation.