Characterization of the Gradient (Mo, Re)Si2/Mo-Re Coatings Deposited in the Hybrid Process

Abstract

Novel siliconized Mo-Re coatings dedicated to applications in the glass industry are shown in this paper. The study aims at the characterization of morphology, phase composition, and oxidation behavior of siliconized Mo-based coatings deposited on a ceramic–metal substrate. Two coatings with different contents of rhenium were prepared using a hybrid process that includes atmospheric plasma spraying and pack siliconizing. The microstructure, chemical, and phase composition of the obtained coatings were characterized and compared to Mo coating. Moreover, a characterization of starting powders was performed. After the description of the coatings’ microstructure, oxidation tests were carried out at 1000, 1100, and 1200 °C. The surface condition of oxidized coatings was investigated. The structure of Re-containing coatings after the siliconizing process was comparable. Both were composed of Mo and (Mo,Re)Si2-ReSi1.75 layers. However, in the case of Mo-44Re (wt.%) coating, a higher concentration of rhenium silicide was observed compared to that of coating containing 15% Re. The Re-containing silicide layers were characterized by a presence of lower content of hexagonal MoSi2 compared to that of non-alloyed MoSi2. The oxidation resistance of both coatings containing rhenium was comparable; however, the one with a higher amount of Re exhibited slightly higher durability in high-temperature oxidation.