Analysis of carboneceous deposits from thermal stressing of a JP-8 fuel on superalloy foils in a flow reactor

A flow reactor study was carried out to investigate the carbon deposition on nickel-, cobalt-, molybdenum-, and iron-based alloy foils during thermal stressing of a JP-8 fuel at 500 degreesC wall temperature and 34 atm (500 psig), for 5 h at a fuel flow rate of 4 mL/min. Temperature-programmed oxidation (TPO) analysis and SEM examination showed that the amount and the nature of the carbonaceous deposits on the foils depend strongly on the chemical composition of the foil surface. The amount of carbon deposited on metal foils decreased in the order Inconel 600 > Havar > Fecralloy > Waspaloy > Hastelloy-C > MoRe > Inconel 718. The presence of minor components, such as Ti, Al, and Nb, in the alloys appears to be responsible for reducing carbon deposition from jet fuel thermal stressing. This effect can be attributed to the formation of a passive layer on alloy surfaces that limits the access of deposit precursors to base metals, Ni, Fe, and Co, that catalyze deposit formation.