Hydrogen-Free CVD Deposition of Molybdenum Coatings

The structure and morphology of CVD molybdenum coatings in the MoCl5–Cd system on substrates made of copper, stainless steel (12Kh18N10T), and Inconel X750 and ZhS6U-VI high-temperature alloys were studied by X-ray diffraction, scanning electron microscopy, and using thermodynamic calculations by the Miedema model. A loose, porous, and thin (0.1 μm) coating was formed on the copper substrate, while uniform and continuous coatings were observed on Inconel X750, 12Kh18N10T, and ZhS6U-VI, which were 0.3, 0.7, and 1.0 μm thick, respectively. In the series of substrates M1–Inconel X750–12Kh18N10T–ZhS6U-VI, the deposition rate of molybdenum increases (from 0.1 to 1.0 μm/h), the size of its crystallites decreases to 50 nm, and lattice microdistortions increase to 0.16%. The rate of deposition of the molybdenum coating based on the MoCl5–Cd mixture is consistent with the negative enthalpy of formation of intermetallic compounds of the equiatomic composition MeMo (where Me is the substrate metal), calculated by the Miedema model. The differences observed in the series of M1–Inconel X750–12Kh18N10T–ZhS6U-VI in the deposition kinetics, morphology, structure, and substructure of the obtained coatings are explained from the standpoint of the enhancement of the adsorption interaction between the substrate and MoCl5 and the chemical affinity of the substrate and molybdenum.