High temperature oxidative stability of C3F7O[CF(CF3)CF2O](x)C3F7 and CF3(OCF2CF2CF2)(y)CF3 perfluoropolyalkylethers and formulations in the presenceof metals (c)

Perfluoropolyalkylethers (PFPAEs) are being extensively evaluated as candid ate high temperature future gas turbine engine oils for the US Air Force. I n order to better recommend fluid formulations for an operational engine sy stem, the following matrix of base fluids, additives and metals was evaluat ed in high temperature oxidation experiments.. Two commercially available b ase fluids ere used, both with C3F6O repeating backbone units, one linear a nd the other branched. Four performance improving additives were used at 1% by weight: a perfluoroalkyldiphenylether, a perfluoroalkyltriphenylether, a tri(perfluoropolyalkyletherphenyl) phosphine and a perfluoropolyalkylethe r bis-benzothiazole. Two sets of metal coupons were used: one set of steels (4140, 52100 410, M50 and 440C) and the other set Ti and Ti alloys (6Al4V, pure Ti and 4Al4Mn). Test temperatures were 260 degrees C to 370 degrees C . In addition, the linear fluid with 1% tri(perfluoropolyalkyletherphenyl) phosphine was also evaluated at 330 degrees C in the presence of thin dense chrome plated M-50, inconel, silver waspaloy and Haynes 214 metals. The da ta are presented and generalizations noted.