Microstructural and ablative properties of graphite nozzles with SiC coating deposited by CVD technique

Abstract

The development of efficient, reliable and affordable propulsion units is one of the main objectives in the development of aerospace technology. Typically the final cost of the vehicle is deeply affected by this subsystem. In this study, a hybrid combination of the ablative chamber is presented where graphite nozzles coated with chemical vapor deposited Silicon Carbide (CVD-SiC) is submitted to the ablative environment, generated by a DC plasma torch operating at a power of 35 kW and homogeneous heat flow of 0.75 MW m ^−2 . The ablative properties of the samples were evaluated by measuring the weight loss as a function of the exposure time, weight loss of 0.11% after 70 s of exposition due to the formation of SiO gas was observed. The microstructure characteristics of SiC coating before and after ablation tests were carried out by SEM and XRD showing that it goes to scale oxidation to forming of SiO _2 ( β -quartz) and SiC ( β to α ) phase transformation. Whereas the ablation mechanism showed to be dependent on the initial coating thickness and exposure time.

Keywords

• rocket engines
• ablation test
• SiC coating
• plasma torch