In Situ Measurement of Stresses in Oxide Scales

A review and comparison of methods for measuring stresses in situ in oxide scale, including x-ray diffraction, Raman spectroscopy, piezospectroscopy, and deflection methods, is presented. An analysis of the principles and procedures of testing has shown that each of them has both advantages and limitations. The results of measuring stresses in various oxides are considered: NiO, Zr₂O, Cr₂O₃, Al₂O₃, etc., studied by different methods. The deflection method is superior to others in measuring stresses in thick oxide scales. However, the coating process brings more errors. In order to eliminate the adverse impacts of coating process, a novel method — Archimedes curve slice moment technique is developed to detect stresses in thick oxide scales on metals for long-term service at high temperature. The experimental principal is illustrated, and the stress formula is derived. Without coating before oxidation, the Archimedes curve slice specimen is oxidized freely at high temperature, and the stresses in oxide scales could be calculated by observing the slice crimping displacement in situ real time during oxidation. A set of the experimental equipment is established, expecting to test the growth stress and thermal stress separately with higher precision.