Modeling Study of Cyclic Oxidation Behavior of NiAl and NiCr Alloys

The cyclic oxidation behavior of four high-temperature alloys (two NiAl alloys and two NiCr alloy) is studied utilizing an existing micromechanics-based model, in which Al₂O₃ and Cr₂O₃ are formed on the alloys as protective layers. For each alloy, the model parameters are determined based on one ‘complete’ experimental curve of weight change, which is obtained under a high-temperature cyclic oxidation test where the weight change experiences a maximum value and then drops down to a zero point. The model is first tested on two metals which have experimental data available for comparison. It is found that the model parameter, oxide crack density exponent, can be assumed constant within a range of high temperature for each metal, thus with the ‘complete’ experimental curve of weight change, the model can predict the oxidation behavior of the metal at different temperatures. The determination of model parameters, accuracy, and limitations of the model for NiAl and NiCr alloys is analyzed and discussed.