Surface modification of heat-resistive materials for gas turbines and basic analyzes by laser spectroscopy

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In this research project have been carried out : experimental evaluation of degradation characteristics of C/C composite materials at high temperatures in methane-air combustion field, improvement of heat resitivity with SiC/glass double layr coating by pac cementation, and analysis of material degradation by in-situ observation using a high speed video camera.1. The following conclusion was given from the experimental studies on the improvement of heat resistirity of C/C composite materials with SiC/glass double layr coating by pack cementation, and optimization of glass layr material for crack-seal.(1) Heat resistivity was significantly improved by adding B_4C into the glass layr, at temperatures below 1573K.(2) The addition of B_4C was not effective at 1773K.However, such a silicide as ZrSi_2 or HfSi_2 improved the heat resistivity.(3) The addition of Al_2O_3 into the glass layr resulted in notable decrease of the heat resistivity.2. In-situ observation of the degradation of C/C composite materials in a premixed plane flame of acetylene with air was made, measuring images of Oh, CH and C_2 band spectra by a high speed spectra video camera (consisting of a monochramator and a high speed video camera), and the followings were concluded.(1) The two-dimensional images of OH and C_2 gave the in-situ information a bout the degradation of the C/C composite surface.(2) The addition of water into the flame increased the degradation of the surface.In summary, it was shown that the addition of ZrSi_2 or HfSi_2 into the glass layr was very effective for the improvement of the heat resistivity of the coated C/C composite materials, and that attacking by OH radicals resulting from H_2O was the main cause of the surface degradation.