CER cutting material

Composites made of ceramic materials in a metallic matrix

Cermets (consisting of ceramic metal) are composites made from ceramic materials in a metallic matrix (binder). They are characterized by a very high degree of hardness and wear. Cermets are mostly used for the finishing process of normal steel at a high cutting speed.

Cermet refers to all types of hard materials. The cermets, therefore, also include hard metals, especially tungsten carbide-free hard metal cutting materials, although there are differences in the manufacturing process (cermets are sinter materials), mechanical behaviour, and interactions between the composite components.

The electrical conductivity is advised as limit to hard metals whereas cermets are considered to be non-conductors [1]. In addition, cermets have a higher thermal shock-and oxidation resistance than sintered carbides. The ceramic components often consist of aluminium oxide (A1203) and zirconium dioxide (ZrO2), while other metallic components such as niobium, molybdenum, titanium, cobalt, zirconium and chromium come into question.

The extreme difference in density between the metallic and ceramic sintered components easily leads to segregation, so that stabilizing additives are required. The sintering process takes place as for homogeneous powders, except for the fact that, given the same pressing force, the metal becomes more compressed than the ceramic.

Cermets based on titanium carbide (TiC) and tantalum carbide (TaC) embedded in a niobium- or more rarely, a cobalt binder phase, are used as cutting material layers. They represent a complex multi-component system with additional elements such as tungsten and tantalum.

The big advantage of using cermets as cutting materials resides in their resistance to temperature fluctuations achieved by the TiC/TaC, which can tolerate heat up to 1,800 °C, thereby making the use of cermets with cooling lubricants possible. The code designation in accordance with ISO 513 for TiC and TaC cermets is HT (hard metal based on titanium-/tantalum carbide). Monolithic milling cutters made of cermet have been unable to take hold due to the low degree of flexural strength.