Cermet

Cermets (composed of Engl. Ceramic and metal) are composite materials made ​​of ceramic materials in a metallic matrix ( binder). They are characterized by a particularly high hardness and wear resistance.

Cermets and hardmetals

The term cermet referred especially in Anglo- American usage all kinds of hard materials. That's why also include the hard metals, especially tungsten carbide - free carbide cutting materials ( sintered materials are cermets), admits the cermets, although there are differences in the manufacturing process in the mechanical behavior as well as the interactions between the composite components. As a border with the hard metals, the electrical conductivity is advised, with cermets are considered non-conductor. Cermets also have a higher thermal shock resistance and oxidation resistance than cemented carbides.

Properties and composition

The ceramic components are often of aluminum oxide ( Al2O3) and zirconia (ZrO2 ) are used as metallic components during niobium, molybdenum, titanium, cobalt, zirconium, chromium and others in question.

The strongly varying density between the metal and ceramic sintered components easily lead to segregation, so that stabilizing additives are necessary. The sintering process proceeds as in homogeneous powders, only that for the same compression force, the metal is compressed more than the ceramic.

Use

Cermets based on titanium carbide (TiC ) and tantalum carbide ( TaC ), that are embedded in a niobium -, molybdenum - cobalt or rare - binder phase, are used as cutting tool material layers. You are a complex multi-component system with other elements such as tungsten and tantalum. The great advantage of cermets as cutting materials is their high thermal shock resistance, which is achieved by the TiC / TaC and can be up to 1800 ° C. Characterized the use of the cermet is also possible with cooling lubricants. The abbreviation according to ISO 513 for TiC and TaC cermets is HT ( hard metal Titan-/Tantalcarbidbasis ). Monolithic cutter cermet have not prevailed due to the low flexural strength.

Various combinations of materials are used as a conductive material or resistive layer in thick film electronic circuits or trimmers. In addition, they have introduced as thermocouple protection tubes in the melt metallurgy and enabled for example, the complete automation of the Linz -Donawitz process.