Abstract: The embodiments of the invention relate to a MoSi2-SiC nanocomposite coating layer formed on surfaces of refractory metals such as Mo, Nb, Ta, W and their alloys. The MoSi2-SiC nanocomposite coating layer is manufactured by forming a molybdenum carbide (MoC and MoC2) coating layers on the surfaces of the substrates at high temperature, and the subsequent vapor-deposition of Si. The MoSi2-SiC nanocomposite coating layer has a microstructure in which SiC particles are mostly located on the equiaxed MoSi2 grain boundary. The MoSi2-SiC nanocomposite coating layer can have a close thermal expansion coefficient to that of the substrate by controlling a volume fraction of SiC particles exisiting in the nanocomposite coating.

Abstract: A NbSi2-base nanocomposite coating formed on the surface of niobium or niobium-base alloys is disclosed. The nanocomposite coating layer is manufactured by forming a niobium carbide layers or a niobium nitride layers by depositing of carbon or nitrogen on the surface, and then depositing silicon. The nanocomposite coating layer has a microstructure that SiC or Si3N4 particles are mostly precipitated on an equiaxed NbSi2 grain boundary. The thermal expansion coefficients of NbSi2-base nanocomposite coating layers become close to that of the substrates by adjusting the volume fraction of SiC or Si3N4 particles in the nanocomposite coating layers. Accordingly, the generation of cracks caused by thermal stress due to the mismatch in thermal expansion coefficient between the NbSi2-base nanocomposite coatings and the substrates can be suppressed, thereby improving the high-temperature oxidation resistance in the repeated thermal cycling use of the NbSi2-base nanocomposite coated substrates.

Abstract: Disclosed are the MoSi2—SiC nanocomposite coating layer formed on surfaces of refractory metals such as Mo, Nb, Ta, W and their alloys. The MoSi2—SiC nanocomposite coating layer is manufactured by forming a molybdenum carbide (MoC and MoC2) coating layers on the surfaces of the substrates at high temperature, and the subsequent vapor-deposition of Si. The MoSi2—SiC nanocomposite coating layer has a microstructure in which SiC particles are mostly located on the equiaxed MoSi2 grain boundary. The MoSi2—SiC nanocomposite coating layer can have a close thermal expansion coefficient to that of the substrate by controlling a volume fraction of SiC particles exisiting in the nanocomposite coating. As a result, the generation of cracks due to the mismatch in the thermal expansion coefficients between the substrate and the nanocomposite coating layer is suppressed and the high-temperature repeated thermal cyclic oxidation resistance and the low-temperature oxidation resistance of the coated substrate are improved.