Micro-arc Oxidation Process and Hot Corrosion Resistance on Niobium Alloy Prepared by Pack Cementation Aluminizing

In order to optimize the micro-arc oxidation (MAO) process of niobium alloy prepared by pack cementation aluminizing, Al2O3 ceramic film was obtained by micro-arc oxidation (MAO) process on aluminizing coating, and MAO electrical parameters and Y(NO3)(3) additive were adjusted to get the optimum process parameters. In addition, hot corrosion resistance of the composite coating(MAO-Y/Al/C103) prepared by the optimal process and MAO/Al/C103 without Y(NO3)(3) were comparatively investigated. Results indicate that the optimum electrical parameters are voltage 380 V, frequency 400 Hz, duty cycle 10% and processing time 30 min. Adding Y(NO3)(3) into electrolyte can obtain uniform porous morphology. The specimens with and without Y(NO3)(3) are both composed of NbAl3 and gamma-Al2O3 phases. Al2O3 and NaNbO3 phases are formed in the MAO/Al/C103 and MAO-Y/Al/C103 with mass gains are 55.71 mg/cm(2) and 45.59 mg/cm(2), respectively, after hot corrosion at 900 degrees C for 50 h. A lot of NaNbO3 forms and MAO micropores decreases dramatically after hot corrosion on the MAO-Y/Al/C103 specimen, exhibiting better hot corrosion resistance.