2004 Volume 45 Issue 9 Pages 2878-2885
Surface alloying of superalloy Haynes 230 was performed using either Al-Mo mixture powders suspended in kerosene or Al-Mo composite electrode during the electrical discharge alloying (EDA). For suspending Al-Mo powders in kerosene, the Cr23C6, WC1−x, and graphite phases exist in the alloyed layer of the EDA specimen with negative electrode polarity, while the specimen with positive electrode polarity exhibits no alloying phase except the raw material phase. For employing the Al-Mo electrode with negative polarity, the specimen represents many discontinuous piled-layers, with Al3Mo8 and AlMo3 phases accumulating on the substrate surface. The specimen produced using Al-Mo electrode with positive polarity shows an alloyed layer constituted mainly with NiAl phase. This specimen also shows the smallest surface roughness and highest hardness among the four EDA specimens. The kinetics of isothermal oxidation at 1000°C in static air demonstrate that the specimen using Al-Mo electrode with positive polarity possesses the best oxidation resistance among the tested specimens.