CERAMICS

Ceramics

Due to their favorable chemical properties, ceramics are of great importance, especially in plant engineering. Ceramic materials also come in useful in power engineering due to their exceptional hardness and temperature resistance, even when exposed to aggressive materials such as acids, alkalis or gases. Extremely varied properties can be achieved by adding alloying and fibrous materials.

Basically, ceramics are divided into oxide and non-oxide ceramics. In the case of oxide ceramics, the whiskers, i.e. fiber reinforcements, are also taken into consideration as an additive for determining the chemical and physical properties. Known materials here are, zirconium oxide ZrO2, aluminum oxide, Al2O3 or the group of sialons based on silicon nitride Si3N4 (a non-toxic ceramic). These materials are generally harder and thus more wear-resistant, like hard metals, but also much more brittle. As a substrate for cutting tools, these materials can only be used under very special operating conditions due to these properties. It is not possible to form such sharp cutting edges as with carbide or diamond. As a result, they build up significantly higher cutting pressures and cutting temperatures.

Non-toxic ceramics have an even higher temperature and corrosion resistance than oxide ceramics. They also have a significantly higher hardness compared to carbide and a greater hardness than oxide ceramics. The most important examples of the non-toxic ceramics are silicon nitride Si3N4 or tungsten WC or boron carbide BC or silicon carbide SiC. A subgroup of the non-toxic ceramics are the fiber-reinforced CMC ceramics, in which carbon fibers are incorporated into a material and then silicified. This is how the familiar ceramic brake discs, which have an enormously high level of hardness and wear resistance, are produced as a result of their temperature resistance. In the future, CMC materials in particular will have a high usage rate in highly efficient engines or gas turbines, as only these materials can meet the requirements of wear resistance under high temperatures.

Green machining close to the final contour

In green machining, ceramics are in a non-fired state. This step is particularly important in the manufacture of components with complex geometry. The aim is to produce the shape of the component to be manufactured as close to the final contour as possible before sinter firing. We recommend the use of our diamond-coated Piranha cutters in full radius, shank, or torus versions for this, Hufschmied Mini cutters in ball or torus cutter version.

White machining with minimum force

During whitening, the fired green ceramic is machined. This process can be optimized using Hufschmied Sharp-Line tools. The very sharp cutting geometry exerts only minimal force on the component. This reliably prevents small particles from breaking out of the component. This is very important because after white firing almost all the binder has been removed from the green ceramic, and the structure is only maintained by the covalent bonding of the ceramic crystal structure. Unfortunately, since these forces are of a very slight nature, care must be taken here to minimize cutting pressure.

Damage-free hard machining

Hard machining of technical ceramics is carried out in the finished fired state. It is important not to introduce any cracks or damage into the component during machining. Our PCD milling cutters and our special drills with full PCD tips or sintered PCD cutting edges are perfectly suited for this step of the job. Only this combination of materials is capable of performing machining with a geometrically defined cutting edge sufficiently well. The only other type of machining is machining with an undefined cutting edge, which is usually very slow and therefore inefficient.

These machining operations, such as milling and drilling, can be supported by the use of ultrasonic vibration systems, as the micro-vibrations introduce small micro-cracks into the material composite, which in some cases significantly simplify the machining process. The diamond tools with the sintered cutting edges or with full-head PCD in particular can offer significant efficiency advantages under ultrasonic impact. Our diamond cutting tools are diamond coated or PCD tipped high performance tools for machining complex materials.