Oxidation resistance of Si-modified aluminide coatings on Mar-M246 superalloy using the halide activated pack cementation technique

Abstract In the present work, the Halide Activated Pack Cementation (HAPC) was adopted to form protective aluminide coatings due to its versatility and low cost. Codeposition of Al and Si on Mar-M246 was performed by HAPC using two different cements constituted of 75 wt.% Al2O3 and 25 wt.% of a mixture formed in different weight ratios of (Al: Si): PM I (50:50) and PM II (72.5:27.5). The coatings are composed in outer part of NiAl and Ni2Al3 phases with significant presence of Si on PM I. After 200 h of oxidation test at 1000 °C, the samples coated by PM I and PM II exhibited the best performance than uncoated one, with mass gains near 0.3 mg/cm2, which is half times the mass gained by uncoated alloy. All coated samples were characterized before and after the oxidation test by SEM, EDS and XRD techniques. The exposure of the coated to high temperature led to the formation of Al2O3 and a modification of the coating morphology by the dissolution of the Ni2Al3 phase.