High-Temperature W/ZrC Composite Coatings

Owing to their outstanding strength, resistance to thermal shock and ablation, high thermal stability, and good thermal expansion, composites of tungsten with zirconium carbide (W/ZrC) have attracted great attention for high-temperature applications. Various techniques can be used for the production of W/ZrC composites, including hot-pressing, spark plasma sintering, in-situ reaction sintering, and displacive compensation of porosity. Both hot-pressing and spark plasma sintering are typically used for preparing small-sized samples with simple geometry. Both in-situ reactive sintering and reactive infiltration methods are well-suited to produce refractory metal/ carbide composites. The reactive infiltration method benefits from a thorough infiltration step because of the good wettability of WC by low-melting metallic liquid of Zr2Cu in a preform to produce a near net-shaped W/ZrC composite. The reaction of zirconium carbide with oxygen can enhance oxidation resistance through the formation of ZrO2 layer which can be melted at a higher temperature (2677 ℃), covering the surface to avoid further oxidation of substrates. Several methods have been reported to deposit the composite on complex-shaped substrates. The results showed good adhesion between coating and graphite substrates as well as a considerable increase in mechanical properties resulting from the formation of solid solution in composites. In this chapter, an attempt has been made to review the preparation of WC preforms which are mainly based on the polymerization of low-toxic methacrylamide and gelation of non-toxic sodium alginate to prepare porous preforms with complex geometries and summarize the preparation methods of W/ZrC composites using reactive sintering and infiltration methods, focusing on microstructures, mechanical properties, and progress in coating applications.