Experimental data on oxide fracture

Abstract

AbstractProtective oxide scales on high temperature materials often fail in service leading to increased oxidation rates. Thus, a knowledge of oxide failure behaviour and failure strains is required. This paper reviews the measured failure strains of chromium oxide and aluminium oxide scales at room and oxide growth temperatures under applied strain. Data on iron and nickel oxide scales are also included for modelling purposes. Failure strains in tension show a power-law dependence on the measured void size within the layer, as expected from fracture mechanics models. Residual tensile or compressive growth and cooling strains prior to loading can increase or decrease the measured failure strains depending on the loading mode, i.e. tension or compression. At growth temperature, lateral oxide growth and creep may act to increase the failure strains, leading in some cases to measured failure strains in excess of 2%. However, the effective failure strains in tension, after taking account of the residual strains, oxide creep, etc., are in most cases less than 0.5% even for the thinnest scales. In compression, the effective values of the failure strains are usually higher than those in tension.Keywords: oxide scalesfracturepower-law dependence