Characteristics of ZrC Barrier Coating on SiC-Coated Carbon/Carbon Composite Developed by Thermal Spray Process

Abstract

A thick ZrC layer was successfully coated on top of a SiC buffer layer on carbon/carbon (C/C) composites by vacuum plasma spray (VPS) technology to improve the ablation resistance of the C/C composites. An optimal ZrC coating condition was determined by controlling the discharge current. The ZrC layers were more than 70 µm thick and were rapidly coated under all spraying conditions. The ablation resistance and the oxidation resistance of the coated layer were evaluated in supersonic flames at a temperature exceeding 2000 °C. The mass and linear ablation rate of the ZrC-coated C/C composites increased by 2.7% and 0.4%, respectively. During flame exposure, no recession was observed in the C/C composite. It was demonstrated that the ZrC coating layer can fully protect the C/C composites from oxidation and ablation.

Ablation behaviour of ZrC coating by novel solid shielding/shrouded plasma spray

“…These cracks act as the channels for oxygen penetration, which result in the oxidation of the SiC inner layer and formation of SiO 2 phase under the surface layer (Figure 15(e,f)). Thus, according to Figure 15, the observation of ZrC and SiC phases under the surface layer confirm the demonstrative effect of ZrO 2 layer as a protective and barrier layer against further oxidation during the ablation test [23,28,30].…”

“…It has been reported that the voids or pores in the coating form due to the unmelted particles, confined vapours, and irregular deposition of splats on each other in the spray process [28,29]. The observed micro-cracks and inter splat cracks (in Figure 8) originate from the rapid solidification of coating from very high-temperatures to room temperature [23,28,30].…”

“…The results showed that the existence of metallic oxides in the coating can affect the phase composition, microstructure, and chemical uniformity that result in the degradation of the coating [22]. By using vacuum plasma spray (VPS) method, the composition of the coating can remain intact and almost as same as the originally sprayed powders [2,23]. But the VPS is an expensive method and has limitations for complex components [9].…”

Emission characteristics of ultrafine particles from bare and Al2O3 coated graphite for high temperature applications

“…Properties such as low neutron absorption, high strength, low thermal expansion coefficient, high thermal conductivity etc. make it a preferred choice for nuclear applications 3 – 5 . Graphite has been tested at all operating conditions of HTRs and has been found to fulfill the operational demands at high temperatures.…”

Special Issue: Advances in Thermal Spray Technology

“…Another paper explores novel surface designs to develop thermally sprayed icephobic coatings [ 4 ]. With the emergence of new engineering materials such as composites, there is also an interest in implementing thermal spray approaches for imparting them suitable protection, as exemplified by the contribution focusing on ZrC barrier coatings deposited on SiC-coated carbon/carbon composites by vacuum plasma spraying [ 5 ]. Post-treatment of thermal sprayed coatings by adopting approaches such as shot peening and laser remelting has also been a subject of considerable academic research.…”