Design of Ceramic-Metal Composites with Novel Architectures

Ceramic-metal composites, or cermets, combine a high hardness ceramic phase with a ductile metallic binder', and are widely used in severe wear and corrosion environments. The proposed research programme involves continued development of TiC and Ti(C,N) based cermets, using high ductility Ni3Al-based binder alloys. Two novel cermet architectures' are proposed in this work: (i) hierarchically structured materials, with constituent phases on nano- to macro-length scales, for high performance wear/corrosion applications, and (ii) lightweight, controlled pore morphology materials, for high energy impact absorption.

The hierarchical cermets will significantly extend our prior studies, through incorporation of industrial diamond particles (0 to 30 vol.% in total) into the cermet microstructure, in combination with graphene additions within the metallic binder (0 to 3 vol.% of the binder volume). Diamond incorporation is expected to increase the cermet hardness and, consequently, the wear resistance, while graphene additions will likely raise the binder yield stress and lower the frictional sliding coefficient. These modified characteristics will significantly improve the wear resistance.

The lightweight, porous cermets will be prepared with both spherical and elongated pores. These materials constitute an entirely new class of engineered' cermet, with controlled architectures'. The primary aim is to fabricate ultra-lightweight, high stiffness cellular materials that can absorb significant energy in compression. To generate a low volume of spherical porosity (0 to 40 vol.%), fugitive starch fillers will be used (following our prior work on porous zirconia ceramics). Higher volume fractions of spherical pores will be generated using a direct foaming technique, which is anticipated to create up to 90 vol.% porosity. Anisotropic pores will be formed through the use of freeze-casting, following our recent collaborative work on alumina ceramics. The porous green bodies will then be densified by reaction sintering or melt-infiltration. Cermet characterisation will include assessment of their microstructures, mechanical and thermal properties, sliding wear behaviour, and aqueous corrosion response.

As an integral component of the research, several HQP (including 3 at PhD level) will receive hands-on training in a wide variety of materials processing and analysis techniques, enhancing their opportunities for subsequent employment in a variety of advanced engineering areas. It is fully expected that this research will result in a significant number of publications, opportunities for knowledge dissemination (e.g. national/international conferences), and the potential to generate valuable intellectual property. Ultimately, successful industrial implementation of these novel materials can be expected to lower maintenance costs in demanding applications.