Behavior of the scale on a 9.5Cr steel under cyclical deformation of the base metal

Abstract

Low cycle fatigue tests have been performed with a 9.5Cr steel at 650°C in air with ramp rates of 7.5 10⁻⁸−7.5 10⁻⁷ sec⁻¹ and deformation amplitudes of ±1% (R=−1). LCF deformation enhances the uniform scale growth as well as nodule formation. This enhancement is caused by repeated scale cracking in the tensile periods of the LCF cycles. The crack-healing process is very rapid and occurs during the deformation process. These processes lead to the formation of a scale rich in iron, because the chromium content of the alloy is too low for protective scale healing.