Speaker
Description
A test campaign was performed in the GHIBLI arc jet facility in the framework of the European funded LIGHT-TPS project, devoted to research and development of Ultra-High Temperature Ceramics (UHTC) coatings on Ceramic Matrix Composites (CMC) for super light-weight Thermal Protection Systems (TPS) of space re-entry vehicles.
Two UHTC coatings made of different zirconium diboride (ZrB2) compositions, ZrB2-3SiC-5WC and ZrB2-20SiC-10AlN, were tested with the aim of increasing the oxidation resistance of the Carbon/Carbon (C/C) CMC substrates. In particular four UHTC coated flat disks of 20 mm of diameter were exposed to an hypersonic jet of plasma composed of air and argon for a total duration of 5÷6 minutes, achieving a maximum surface temperature of 1800÷2000°C at stagnation pressures of 23÷25 mbar. The UHTC coating made by ZrB2-20SiC-10AlN survived the tests forming an oxidized surface layer.
Three different pyrometers have been used to measure the surface temperature in the disk stagnation area. During the tests, one pyrometer was repeatedly switched from two-color to single-color mode in order to evaluate the experimental emissivity of the surface at different temperatures. At the end, in the range of temperature from 1700 to 2000°C the measured spectral emissivity values at the wavelength of 0.9 μm varied between 0.5 and 0.8 for ZrB2-3SiC-5WC samples and between 0.6 and 0.4 for ZrB2-20SiC-10AlN ones.
Summary
Spectral emissivity evaluation in plasma wind tunnel of UHTC coatings
