Evolution of the phase composition of ZrB2-35MoSi2-15Al composite coating at annealing

Abstract

In this article, new composite coatings ZrB2-35MoSi2-15Al were deposited on the surface of a carbon-carbon composite using a multi-chamber detonation accelerator. The evolution of the phase composition of ZrB2-35MoSi2-15Al coatings was analyzed with differential scanning calorimeter (DSC) and X-ray diffractometry (in situ HT-XRD) at temperatures from room temperature (∼ 25°C) to 1400°C (normal atmosphere and pressure). The coating before annealing according to X-ray diffractometry data is tetragonal (t-ZrO2) and monocline (m-ZrO2) zirconium dioxide, monocline silicon oxide (m-SiO2), hexagonal zirconium diboride (h-ZrB2), tetragonal molybdenum disilicide (t-MoSi2), cubic aluminum (c-Al) and cubic yttrium oxide (c-Y2O3). It was found that the coating crystallizes in m-ZrO2 at 460ºC, and then mullite with rhombic crystal lattice appears at 960ºC. When the temperature reaches 1050ºC the m-ZrO2, ZrSiO4, t-ZrO2, m-SiO2 and mullite phases formed in the coating. At 1400 º C, cubic zirconium dioxide appears in the coating. Experimental results can become the basis for the application of ceramic coating ZrB2-35MoSi2-15Al, which can improve the properties of carbon-carbon composites in an oxygen-containing environment at elevated temperatures.