In situ synthesis of oxidation and wear resistant coatings on graphite

Carbon based materials are considered as preferred materials in applications requiring high strength, high refractoriness, thermal shock and thermal stresses in extremely harsh environments. However, these materials are extremely vulnerable to oxidation at exalted temperatures. Efforts have been made to shield such materials from oxidation at high temperatures by the introduction of dense and crack free surface coatings, impregnates and oxidation retardants. Some refractory carbides, borides and silicides offer potential coating systems for such materials. Metal carbide coatings have been found useful for carbon base materials. This coating is formed at high temperature normally above 1500°C. The present work is related to the formation of a high temperature oxidation and wear resistant coating of Titanium Carbide (TiC) on polycrystalline graphite substrate at lower temperatures. The coating was prepared by Halide Activated Pack Cementation (HAPC) process at temperatures below 1500°C. Various catalysts including Fe, Ni, and iodine had been used to reduce the temperature of the process. Resulting coatings were characterized by using optical microscopy and Energy Dispersive X-Ray Spectroscopy (EDX). Optical microscopy was used for the microstructural analysis and measurement of coating thickness. Elemental and chemical analysis was performed using Energy Dispersive X-Ray Spectroscopy (EDX). Furthermore, the effect of variation in composition ratio, operating temperature and time of cement can be used to optimize the properties and thickness of TiC coating formed on specimen.