Ablation resistant properties and mechanism of ZrC coating deposited by plasma-spraying

The comparatively dense W bonding layer and ZrC ablation-resistant layer were deposited by plasma spraying on C/SiC composite substrate. The ablation resistant properties were tested by oxyacetylene flame. The results show that the coatings have good ablation resistant properties. Ablated by oxyacetylene for 30 mm and 300 s, the mass ablation rate of ZrC coating is 1.7×10^-3 g·s^-1, only 68% of uncoated specimens; linear ablation rate is 4.0×10^-4 mm·s^-1, only 30% of uncoated specimens. With decreasing the ablation distance, the coating mass ablation rate increases, and the linear ablation rate decreases. Because of the temperature gradient caused by the oxyacetylene on the surface of the sample, the coating forms three kinds of ablation apparent morphology after ablation, including the central dense area, the transition area and the edge of loose area. In the central region, WO₃ is melted due to high temperature, and effectively fills in the holes and cracks of the coating. In the end, a dense layer is formed, whereupon reducing the mechanical denudation, and the thermochemical corrosion plays a major role. In the marginal area, the ablation products are not melted due to low temperature and they are loose. The anti-ablation forms are mainly thermochemical corrosion and mechanical erosion.