MEASUREMENT METHODS TO DETERMINE THE ELASTIC PROPERTIES OF OXIDES AT ELEVATED-TEMPERATURES

Knowledge of the elastic properties of oxide scales has long been reco gnized as important in the understanding of how oxide scales fail at t emperature. This paper examines the available measurement methods capa ble of determining the elastic properties of oxide scales. In the late 1960s a resonant frequency method was proposed that permitted the oxi de modulus to be calculated from measurements of the stiffness of an o xidizing rod and knowledge of scale growth rates. This technique was t he first to provide an 'in situ' method of measuring oxide properties at temperature. Recent developments now permit a fully automated measu rement 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 materi als at elevated temperatures are examined and their applicability to t he in situ measurement of oxide elastic properties discussed. From thi s analysis it would appear that transient wave excitation methods offe r the potential of rapid measurement of the resonant frequency of an o xidizing sample in situ and would be capable of utilizing the analyses developed for resonant frequency to determine the oxide modulus.