Effect of lattice surface treatment on performance of hardmetal - titanium interpenetrating phase composites

Additive Manufacturing (AM) of metals by the Selective Laser Melting (SLM) process has attracted wide attention in recent years due to its potential to increase specific properties of metals and alloys beyond the capacity of bulk materials. SLM can be used to fabricate cellular lattice 3D structures from a wide variety of metals. This research has applied these structures as the basis for the fabrication of a new type of Interpenetrating Phase Composites (IPCs). IPCs were fabricated by filling titanium cellular lattice structures with hardmetal (WC-Co) powder and subsequent consolidation by Spark Plasma Sintering (SPS). A special attention was drawn on the influence of the interphase between titanium and WC-Co phases. In order to alter the extent of chemical reactions and diffusion during the consolidation process, surface nitriding and carburizing of the titanium lattice were carried out. The present research findings demonstrate that by applying AM, metal - ceramic IPCs can be fabricated. The developed IPCs manifest unconventional mechanical properties such as decreased elastic modulus and high strain values, which have not been observed for hardmetals so far made by conventional means. Under compressive loading similar to 10% of the deformation was observed in the IPCs before a catastrophic failure. The principal constituents of hardmetals (tungsten carbide and cobalt) are defined by the EU as critical and in the case of cobalt as dangerous to health. Usage of both of these elements will be considerably decreased in wear resistant parts, if standard hardmetal tools are replaced by such novel IPCs.