Microscale fracture of chromia scales
September 29-October 4, 2019
High temperature materials such as superalloys rely on the formation of a protective surface oxide scale for prevention of corrosion. Such materials undergo periods of varying thermal and mechanical loads during operation, which can lead to cracking of the surface oxide. This exposes the material to corrosion, and can also act as stress concentrations, which affects the life of the underlying material. It is therefore necessary to consider the mechanical integrity of these scales while estimating material life. Several models have been developed in which fracture mechanics is utilized to estimate failure. But there is a lack of data such as fracture strains and elastic modulus for oxide scales. Conventional mechanical testing methods such as tensile and bending tests have been modified to obtain mechanical data, but it mainly applies to thick oxide scales (several µm thick). These methods are also limited with respect to isolating substrate and residual stress effects. For advanced materials, where the oxide formation kinetics are low, new methods are required in order to assess the mechanical properties.
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Anand H. S. Iyer, Gaurav Mohanty, Krystyna Stiller, Johann Michler, and Magnus Hörnqvist Colliander, "Microscale fracture of chromia scales" in "Nanomechanical Testing in Materials Research and Development VII", Jon Molina-Aldareguia, IMDEA-Materials Institute, Spain Eds, ECI Symposium Series, (2019). https://dc.engconfintl.org/nanochemtest_vii/32