Protection of a microstructured molybdenum reactor from high temperature oxidation by electrochemical deposition coatings in molten salts

To improve the corrosion resistance of molybdenum, different methods were applied in this study: electrodeposition of hafnium coatings, electrochemical synthesis of hafnium diboride, boronising, siliciding, and boronising of MoSi2. The oxidation resistance of the coatings was investigated by the weight change in an air—water (2.3 vol %) mixture at a temperature of 500°C for a period up to 700 h. The best results for coatings with a thickness around 5 jim were obtained by boronising of silicided molybdenum substrates (MoSi2/Mo). It was shown that a two-phase microstructure consisting of the MoSi2 matrix phase with 12—15 wt % of the MoB4 phase greatly improved the oxidation resistance of the molybdenum substrate. The weight gain improved the oxidation resistance of the molybdenum substrate. The weight gain observed was 6.5 x I 0~ mg . cm~2 . h-