Evaluation of the environmental degradation of interphases in Ceramic Matrix Composites (CMCs) via in-situ SEM micromechanical testing
September 29-October 4, 2019
The need to increase the cycle efficiency and reduce NOx emissions from aero-engines has promoted the development of Silicon Carbide (SiC) based Ceramic Matrix Composites (CMCs) which have entered in service in aircraft turbine engines as replacements for some Ni-based superalloys. The main tendency of material choice is converging to CMCs constituted by SiC fibres coated with a thin (0.1-1 µm) BN interphase within a SiC matrix (SiC/BN/SiC), resulting in an optimised tough ceramic composite. However, unlike the generic tendencies found for metallic materials, environmental effects seem to not follow a clear tendency as hottest temperatures do not necessarily result in more severe degradation. This is due to the complex degradation thermodynamics occurring at the interface of the SiC-BN system such as volatilisation of B species, borosilicate glass formation or formation of self-healing oxide products.
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Oriol Gavalda Diaz, Finn Giuliani, Katharina Marquardt, Luc Vandeperre, Eduardo Saiz, Louise Gale, Ian Edmonds, and Stephen Harris, "Evaluation of the environmental degradation of interphases in Ceramic Matrix Composites (CMCs) via in-situ SEM micromechanical testing" 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/110