RETRACTED ARTICLE: Ablation Behavior of SiC/ZrB2 Multilayer Coating Prepared by Plasma Spray Method

In this study, a SiC/ZrB2 multilayer coating with a functional gradient structure was prepared on graphite to increase the ablation resistance. The SiC coating as the inner layer was applied by the reactive melt infiltration method. Then, a ZrB2 outer layer coating was applied by argon gas shrouded plasma spray. The effect of the shielding gas flow rate on the amount of oxides and quality of the ZrB2 coating was studied. To evaluate the ablation resistance of the coatings, the specimens were exposed perpendicular to an oxy-propane flame for 60 second with a temperature of 2473 K and heat flux of 3000 kW/m2. The single-layer SiC coating showed 24.24 pct mass loss. The results indicated that applying the ZrB2 coating significantly improved the ablation resistance and reduced the mass ablation rate. In the plasma spray process, by applying the argon shrouding with a flow rate of 150 L/min, the oxidation of ZrB2 phase decreased from 41.6 to 4.8 pct. In addition, the weight loss and mass ablation rate decreased from 12.79 and 1.857 × 10−3 g/cm2/s to 0.12 pct and 0.0393 × 10−3 g/cm2/s, respectively. The improvement of the ablation resistance of the coating prepared by argon gas shrouded plasma spray could be attributed to the lower amount of oxides and pores in the as-sprayed coating and better cohesion of splats.