The Oxidation Behavior and Mechanism of Plasma Spraying ZrB₂ Ceramic Coating with SiC Addition

Plasma spraying ZrB₂ ceramic coating is considered as potential candidate method of Thermal Protective System. While the application of plasma sprayed ZrB₂ coating is restricted due to its oxidation. Therefore, it is important to study the oxidation behavior of the ZrB₂ material. In this research, oxidation behavior of the ZrB₂ ceramic, which achieve different density by using SPS and pressureless sintering, is studied to explain the oxidation behavior of plasma spraying ZrB₂ ceramic coating. The oxidation behavior of ZrB₂ ceramics is investigated using SEM, XRD and EDS. The ZrB₂–based ceramic coating is gravely oxidized at 600°C, but the block ZrB₂–based ceramics also possess excellent oxidation resistance above 1000°C. The density of ZrB₂ ceramics significantly increase when changing the sintering method from pressureless sintering to SPS. The high density has beneficial effect to improve the oxidation resistance of ZrB₂ ceramic, for there are few open pores channel in high density ceramics. The oxygen cannot diffuse to the inner through pores, as a result, the high density ceramics can only be oxidized from outside to inside progressively, unlike low density ceramics, whose surface and inner is oxidized simultaneously.