Measurement methods to determine the elastic properties of oxides at elevated temperatures

Abstract

Knowledge of the elastic properties of oxide scales has long been recognized as important in the understanding of how oxide scales fail at temperature. This paper examines the available measurement methods capable of determining the elastic properties of oxide scales. In the late 1960s a resonant frequency method was proposed that permitted the oxide modulus to be calculated from measurements of the stiffness of an oxidizing rod and knowledge of scale growth rates. This technique was the first to provide an ‘in situ’ method of measuring oxide properties at temperature. Recent developments now permit a fully automated measurement of oxide elastic properties on both rod-shaped and rectangular specimen geometries. These new developments are reviewed. Alternative methods that are available to measure the elastic properties of materials at elevated temperatures are examined and their applicability to the in situ measurement of oxide elastic properties discussed. From this analysis it would appear that transient wave excitation methods offer the potential of rapid measurement of the resonant frequency of an oxidizing sample in situ and would be capable of utilizing the analyses developed for resonant frequency to determine the oxide modulus.