LNGロケットエンジンにおけるサルファアタック防止に関する研究 : —金メッキの防止効果について—

概要

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Liquified natural gas (LNG) is one of the most promising propellant for the near future space transportation rocket engine because of its low cost and fewer handling concerns. However, for LNG propellant, erosion of engine material by sulfur (sulfur attack) is significant problems such as blockage at the regenerative cooling passage and the material strength deterioration in regenerative cooling passages. In this study, the effect of sulfur attack is experimentally evaluated for nozzle material candidate such as Inconel600 (AMS5540M) and combustion chamber material candidates such as SMC, OMC (copper-chrome-zirconium alloy) and OFHC (JIS C1020P 1/2H). And this study apply gold coating at the regenerative cooling passages of the LNG rocket engine chamber and performance of the protection method against sulfur attack is experimentally evaluated for gold coating. In the sulfur attack test, EPMA and Raman analyses indicate that metallic sulfide can be observed on the surface and cathodic reduction indicate that depth of the sulfide is between 1μm and 8μm for SMC, OMC and OFHC. Tensile test also indicates the tensile stress slight decrease with Inconel600 (AMS5540M) and SMC. On the other hand, in the coating test, formation of metallic sulfide and depth of the sulfide has been reduced by gold coating. The results of the this study shows that beneficial effect of gold coating against sulfur attack.