C/SiC Gradient Oxidation Protective Coating on Graphite by Modified Reactive Melt Infiltration Method: Effects of Proces
- PDF / 6,626,420 Bytes
- 14 Pages / 593.972 x 792 pts Page_size
- 44 Downloads / 162 Views
CARBON-BASED materials are a generic class of advanced materials that can be made in a wide variety of forms such as C/C composite, graphite, and C/SiC composite. These materials are attractive for application in high-temperature structural components[1] such as nozzles, leading edges, nosetips, body flaps, brakes, hot gas path components, and thermal protection systems for space vehicles.[2] Although carbon-based materials have good high-temperature properties, including high thermal shock resistance, high thermal conductivity, low coefficient of thermal expansion, and high specific strength, if they are exposed to the oxygenic atmosphere at temperatures higher than 773 K (500 °C), they will be rapidly oxidized. In other words, carbon materials have high strength and stiffness potential as well as high thermal and chemical stability in inert environments. These materials must, however, be protected with coatings and/or surface sealants when used in oxidizing environments.[3] SiC coatings can effectively protect the carbon materials from the high-temperature oxidation. ALIREZA ABDOLLAHI, Ph.D. Candidate, and NASER EHSANI, Professor, are with the Faculty of Materials & Manufacturing Processes, Malek Ashtar University of Technology (MUT), P. O. Box: 15875-1774, Tehran, Iran. Contact e-mail: alirezaabdollahi1366@ gmail.com, [email protected] Manuscript submitted June 13, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
This is attributed to the formation of a self-sealing silica glass layer on the surface.[4] This glassy layer has a very low oxygen permeability.[5] SiC coatings are produced on carbon materials by different methods such as vacuum plasma spray,[6] electrophoretic deposition (EPD),[7] reactive melt infiltration (RMI),[8] chemical vapor deposition (CVD),[9] chemical vapor reaction,[10] etc. For instance, Sun et al.[11] prepared ZrSiO4/SiC coating on C/C composites by supersonic plasma spraying. They attributed the excellent oxidation-resistant properties of the coating to the formation of the stable ZrO2-SiO2 glassy layer on the surface. Yang et al.[12] prepared SiC-B4C self-healing coating on C/SiC composite by chemical vapor deposition (CVD). They illustrated that the SiC-B4C coating was more efficient to protect the composite from oxidation than was the SiC-SiC coating below 1273 K (1000 °C) due to the self-healing behavior. At temperatures above 1473 K (1200 °C), though, the SiC-SiC coating showed better oxidation resistance than that of SiC-B4C coating due to the enhanced evaporation of B2O3 at higher temperature. Li et al.[13] compared the oxidation behavior of SiC coatings on C/C composites prepared by pack cementation and chemical vapor deposition. They showed the oxidation protective ability of the CVD-SiC coating was worse than that of the pack cementation-SiC coating because of the higher viscosity of SiO2 glass and the inferior interface adhesion between the coating and the substrate.
Compared with other methods, RMI, which is considered a diffusion process, is a common method to produce functional
Data Loading...
