Microstructure of Spark Plasma Coated Ultrahigh Temperature ZrB₂–SiC–Si Composites on Graphite Substrate

In this article, ZrB₂–SiC–Si layers were applied on graphite substrate employing SPS technology. Additives such as MoSi₂ and WC were also used to improve sinterability, increase adhesion and proper bonding between the applied composite layer and the graphite substrate. To select the optimal sample in terms of densification, adhesion and bonding between the substrate and the applied composite layer, microstructural and phase studies were performed on the composite layers. The Si penetration depth in the graphite substrate in the ZrB₂–14.3 vol% Si–14.3 vol% SiC–2.5 vol% MoSi₂ –2.5 vol% WC sample, made at 1890 °C under 25 MPa for 5 min, was more than 165 µm, and the thickness of the penetration layer composed of SiC–C was more than other samples. The densification process in this sample was almost complete and a dense structure was obtained.