Recycling of MoSi2-based industrial solid wastes for the fabrication and high-temperature oxidation behavior of MoSi2–ZrSi2–SiC composite coating

Abstract

To protect Nb substrate from oxidation at elevated temperatures and make better use of the industrial solid wastes, spent MoSi2 heating elements, ZrSi2 and SiC were applied as raw materials to prepare MoSi2 and MoSi2–ZrSi2–SiC coatings by Spark Plasma Sintering (SPS). After high-temperature sintering, cracks were found in a single MoSi2 coating while MoSi2–ZrSi2–SiC coating was crack-free without any defects by the CTE mismatch reduction. Diffusion layers formed on the substrate and it strengthened the bonding in the coating system with good metallurgical combination. The oxide scale of the composite coatings possessed compact and crack-free morphologies with fractional consumption after oxidation at 1500 °C. Circular Mo5Si3 phases that possessed pores and cracks generated in the silica layer of MoSi2 coating at 1700 °C while MoSi2–ZrSi2–SiC composite coating still kept crack-free oxide scale, thus showing excellent 1700 °C anti-oxidation properties.