Long-term isothermal oxidation behavior of two industrial polycrystalline nickel base alloys in air at 700 °C-Evaluation of intergranular oxidation distribution and kinetic

Chromia forming Alloy 718 and AD730TM have been submitted to isothermal long-term air exposure up to 10 000 h at 700 degrees C. The resulting very low specific mass gain led to consider two alternatives to determine the oxidation kinetics. Measurements of the external layer thickness and of the intergranular oxide amount were carried out on SEM micrographs evidencing the intergranular oxidation contribute around 30% to the total specific mass change. AD730TM with a thicker external scale and a higher amount of intergranular oxide showed a twofold faster oxidation rate than Alloy718. The results demonstrated the need of even longer tests.

Automated summary

Chromia forming Alloy 718 and AD730TM were subjected to isothermal long-term air exposure at 700 degrees C for up to 10,000 hours. The study found that intergranular oxidation contributes around 30% to the total specific mass change. AD730TM exhibited a twofold faster oxidation rate compared to Alloy718, indicating the need for even longer tests to confirm the results.