A Cr-Al-Si oxidation resistant coating for carbon/carbon composites by slurry dipping

摘要

Carbon/carbon (C/C) composites have been considered as one of the most important materials for aerospace and re-entry vehicle application due to their excellent high temperature mechanical properties and thermal shock resistance [1,2]. However, the easy oxidation of C/C at temperatures above 723 K limits greatly their applications at oxygen containing atmosphere [3]. To improve their oxidation resistance, a multi-layer protective coating using SiC as an internal buffer layer has been proposed [4 7]. Al Si alloy [8] is expected to have an excellent oxidation protective ability because a SiO_2 glass film for crack self-curing and Al_2O_3 barrier layer for baffling infiltration of oxygen can be generated on the coating surface at high temperature, though Al-Si alloy is not stable at high temperatures due to its low melting point. Since Cr-Al-Si alloy ingot produced by Worrel, with arc melting process showed a good oxidation resistance with no mass loss after oxidation in air at 1823 K for 280 h [9], it might be used as the promising coating material for C/C composites for application at high temperature. Little research, so far, has been reported about using Cr-Al-Si alloy as the oxidation resistant coating for C/C composites. In order to improve the oxidation resistance of C/C composites for application at 1773 K, Cr-Al-Si alloy coating was prepared on the surface of SiC coated C/C composites by a low cost approach of slurry dipping method. The microstructures and oxidation protection ability of the coatings were investigated.