SiC–SiCf CMC manufacturing by hybrid CVI–PIP techniques: process optimisation

SiC–SiCf ceramic matrix composites (CMC) are candidate structural material for fusion power reactor applications because of their favourable thermo-mechanical and low-activation properties. Among their different manufacturing techniques, present, the most employed ones are chemical vapour infiltration (CVI) and polymer infiltration and pyrolysis (PIP). These two techniques are based on the common principle of filling the porosity among the fibres with SiC resulting from precursor decomposition. CVI process deposits high purity crystalline SiC with good properties onto fibres whereas PIP leaves lower characteristic amorphous SiC with traces of oxygen between fibres. PIP, on the other hand, seems to be much more industrially effective than CVI. In the attempt to maximise the properties and reduce costs, some work has been done on the so called ‘hybrid techniques’ in which CVI and PIP are both employed. The work performed by ENEA and FN S.p.A. consists of a series of combined CVI–PIP process cycles and the subsequent product characterisation.