Vacuum repair brazing of Inconel 939 using various ratios of DF3 and Rene 80 powder mixtures has been performed in this study. The porosity of the brazed zone is decreased as the amount of DF3 is increased in the powder mixture. At least four phases are observed in the brazed zone including chromium borides, sparse carbides, Ni-rich matrix and eutectic phases. Primary chromium borides are widely observed at the early stage of repair brazing. Dissolution of the Ni from the Rene 80 powder into the molten braze results in isothermal solidification of the residual melt. The chemical composition of the residual melt subsequently moves towards the lowest eutectic temperature, and the eutectic is finally formed in brazing. The oxidation resistance test is performed at 1000oC. Extensive spalling of the oxide film begins at 144 h, and catastrophic failure of the oxide film is observed at 1272 h. The oxidation resistance of the brazed zone is significantly degraded due to the formation of chromium borides in the brazed zone.