Effect of an applied stress on the growth kinetics of oxide scales formed on Ni-20Cr alloys

Abstract

The effect of a tensile load on the oxidation rate and mechanism of Ni–20Cr was studied at 600 and 900°C by comparing samples oxidised in air either classically or under tensile creep. The objective was to understand the simultaneous effect of the environment and mechanical loading. Applying a tensile load does not modify the oxide layer nature but the oxidation rate is enlarged due to the increase of oxygen diffusion via fast diffusion paths generated when the strain is higher than a critical value. Thus, at 600°C, oxygen in excess promotes internal oxidation and the oxide layers are thicker than when formed without any load. At 900°C, for small oxidation times, the spinel layer is enlarged, while for longer times, the spinel layer progressively disappears and the excess of oxygen diffusing inward reacts with chromium to form a thicker Cr₂O₃ layer.

Keywords:

• Ni–20Cr
• oxidation rate
• creep
• strain effect
• oxidation mechanism
• oxidation–deformation interaction