Ablation Resistance Of (Hf,Zr)C Solid Coating For C/C Composites

In order to improve the corrosion resistance of C/C composite above 2500℃,C/C composite was modified and HfC-based multilayer solid solution composite coating was prepared.In this paper,the high-temperature chemical reaction method and the plasma spraying method are combined,with the HfC as the main body,Zr C,Ta C and SiC as the added phases.On the basis of analyzing the high temperature corrosion resistance properties of SiC,HfC-SiC and（Hf,Zr）C-SiC,the ablation properties and mechanism of（Hf,Zr）C/SiC double-layer coating under different ablation conditions and different HfC/Zr C ratio were studied,the effects of Zr C-SiC and Zr C-Ta C on the ablation properties and mechanism of（Hf,Zr）C in three layers were investigated,the ablation properties and mechanism of（Hf,Zr）C solid solution gradient coating were studied.The results are as follows:（1）SiC,HfC-SiC（Hf Si₂ and Hf Si₂+Si）,（Hf,Zr）C-SiC single-layer coatings were successfully prepared by high-temperature chemical reaction method.After an oxyacetylene flame ablation test of 20s with a heat flow density of 3.2MW/m²,the line ablation rate of（Hf,Zr）C-SiC and HfC-SiC（Hf Si₂+Si）coating was-0.0045 mm/s and 0.0065mm/s,respectively;the mass ablation rates were 0.0046g/s and0.0003g/s,respectively.For 60s and 30s plasma flame ablation experiments of SiC and HfC-SiC（Hf Si2）coating,the mass ablation rate was 5.810^-4g/s and 3.610^-5g/s,respectively.SiC coating remained largely unchanged after ablation,small ablation pits appear in the ablation center of the HfC-SiC coating.（2）The（Hf,Zr）C/SiC double-layer coating（HfC/Zr C ratio of 2:1）was prepared by the high-temperature chemical reaction method and plasma spraying method.After an oxyacetylene flame ablation test of 60s with a heat flow density of 3.2MW/m² and 20s with a heat flow density of 4.2MW/m,the line ablation rates was 0.0003mm/s and0.0035mm/s,respectively;the mass ablation rates was 0.00078g/s and0.0144g/s,respectively;the maximum temperature on the sample surface is about 2400℃.Then,performed the plasma flame ablation experiments for 54s,The highest surface temperature was 2812℃and the mass ablation rate was 0.0655g/s,an ablation pit appears in the ablation center.When the HfC/Zr C ratio is 1:1,after an oxyacetylene flame ablation test of 20s with a heat flow density of 4.2MW/m²,the line ablation rate is0.0030mm/s and mass ablation rate is 0.0108g/s,the highest material surface temperature is 2739.51℃,the Zr C content makes the coating form a dense oxide film,and the surface temperature increases.（3）Through high temperature chemical reaction method and plasma spraying method,the（Hf,Zr）C/Zr C-SiC/SiC and（Hf,Zr）C/Zr C-Ta C/SiC tripe coating and（Hf,Zr）C solid gradient coating has been successful prepared.After an oxyacetylene flame ablation test of 20s with a heat flow density of 4.2MW/m²,the line ablation rates were0.0050mm/s,-0.0030 mm/s and 0.0080 mm/s respectively;the mass ablation rates were 0.0238g/s,0.0074g/s and 0.0271g/s,respectively;the maximum temperature on the sample surface was about 2700℃.During the ablation process,the low melting point group in the middle layer will spread to the outer layer and form a dense oxide film in the outer layer.