Effect of Boron Addition on Oxide Scale Formation of Ni-Base Superalloys
In the present investigation the air oxidation behaviour of two commercially available B containing Ni base alloys (Rene80, CM247) was studied at temperatures in the range 850°C to 1050°C. After various exposure times up to 100h the oxidized samples were investigated with a number of analysis methods, including glow discharge optical emission spectroscopy (GD-OES), optical and scanning electron microscopy (SEM combined with EDX/WDX and EBSD) as well as X-Ray diffraction.
B was found to become incorporated into the oxide scale whereby the participation in the oxidation process strongly depended on alloy composition. The oxidation of B resulted in its depletion from the bulk alloy and was found to be dependent on the exposure conditions, being stronger at higher exposure temperatures and longer exposure times. A modelling approach is presented to correlate B incorporation in the surface oxidation process with its depletion in the bulk alloy.