Oxidation of Ni-Cr alloy at intermediate oxygen pressures. II. Towards the lifetime prediction of alloys

• Oxidation of Ni-30Cr alloy has been performed at 1150 °C in Rhines packs.
• Kirkendall porosities are formed in the alloy during oxidation.
• Chromium depletion profiles in the alloy have been analysed.
• The interdiffusion coefficient is equal to 1.2 × 10−12 cm2 s−1.
• A predictive model for chemical lifetime estimation of alloys is proposed.

The formation of protective Cr2O3 layer on Ni-Cr alloys depends on (i) the chromium concentration at the alloy/oxide interface and (ii) the chromium diffusion in the alloy from the core towards the surface. A sufficient interfacial chromium content and chromium gradient are necessary to sustain the selective external oxidation of chromium. Ni-30Cr samples have been oxidised at 1150 °C in 10−13 up to 10−3 atm O2. Analytical methods are used to model the diffusion in steady-state conditions and to predict the lifetime of the alloy. The interdiffusion coefficient is found equal to 1.2 × 10−10 cm2 s−1.