Advanced testing for ranking coating/material combinations
Structural Ceramic Matrix Composite (CMC) components have significant commercial potential in land-based power generation. The HITHEX EC-funded project focused on the demonstration of their applicability in high and ultra high heat exchangers. Researchers employed low cost C/C-SiC materials derived from a previous project, which before the manufacture of structural CMC-components had to be further improved. One of the key problems that need to be improved is the chemical corrosion and/or oxidation effects that these materials display when they undergo manufacture processing steps. Thereby, optimisation of oxidation protection of the material is highly required in terms of its thermal shock behaviour. This is why part of the project work involved the development of a critical test, the so-called thermal cycling testing. Answering this need IE-JRC developed a rapid test that can accurately identify thermal property mismatches allowing ranking of various coating/material combinations. The test uses a furnace capable of accommodating complex environments, whose operation involves transportation of test materials into and out of the hot zone. Complementary to this thermocyclic oxidation testing is the complex corrosion testing, where the oxidation/corrosion resistant properties of different ceramic composite materials are tested. Proper measures were taken in the design of the methodology taking into account that the test materials are extremely sensitive to oxidation. Weight loss is measured during the inter-cycle downtime showing that the breakdown of the oxidation/corrosion protection coating is completed. The new testing methods offer simulation presentation of the loading and failure behaviour of materials under realistic conditions allowing the development and improvement of materials aimed for structural components.
