Ceramics, chemicals, silicon

Ceramics, chemicals, silicon

Ceramics, chemicals, silicon

Due to their positive chemical properties, ceramics are particularly important in plant construction. Ceramic materials are also suitable for energy technology due to their exceptional hardness and temperature resistance, even when exposed to aggressive media such as acids, alkalis or gases. Extremely different properties can be achieved by adding alloy and fiber materials.

Basically, ceramics are divided into oxidic and non-oxidic ceramics. In the case of oxidic ceramics, the possible whisker reinforcements, i.e. fiber reinforcements, also come into consideration as an additive for determining the chemical and physical properties. Well-known materials here are, for example, 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 therefore more wear-resistant than hard metals, but also significantly more brittle. Due to these properties, these materials can only be used as a substrate for cutting tools under very special operating conditions. The cutting edges cannot be as sharp as with hard metal or diamond. As a result, they build up significantly higher cutting pressures and machining temperatures.

The non-toxic ceramics have a significantly higher temperature and above all corrosion resistance than the oxidic ceramics. They also have a significantly higher hardness than hard metal and also a higher hardness than oxidic ceramics. The most important representatives of non-toxic ceramics are silicon nitride Si3N4 or also 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 embedded in a material and then siliconized. This is how, for example, the well-known ceramic brake discs, which have an enormously high hardness and an enormously high wear resistance, are created due to their temperature resistance. In the future, CMC materials in particular will have a high degree of use in highly efficient engines or gas turbines, since only these materials can meet the requirements for wear resistance at high temperatures.

Green processing close to final contour

In green processing, ceramics are in an unfired state. This step is particularly important when manufacturing components with complex geometries. Attempts are made to produce the shape of the component to be manufactured as close as possible to the final shape before sintering. We recommend the use of our diamond-coated Piranha milling cutters in full radius, shank or torus versions. Hufschmied Mini cutters in spherical or torus cutter versions.

White processing with minimal force

During white processing, the fired green ceramic is machined. This process can be carried out using the tools of Hufschmied Optimize sharp line. The very sharp cutting edge 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 of the binder has been removed from the green ceramic and the structure is only preserved through the covalent bonding of the ceramic crystal structure. Since these forces are unfortunately only of a very small nature, care must be taken to ensure that the cutting pressure is as low as possible.

Damage-free hard machining

The hard processing of technical ceramics takes place in the fully fired state. Here it is important not to introduce any cracks or damage into the component during processing. Our PCD milling cutters and our special drills with solid PCD tips or sintered PCD cutting edges are perfectly suited for this work step. Only this combination of materials is able to carry out machining with a geometrically defined cutting edge sufficiently well. The only other type of processing is machining with an indefinite cutting edge, which, however, is usually very slow and therefore inefficient. 

These types of processing, such as milling and drilling, can be supported by the use of ultrasonic vibration systems, since the micro-vibrations introduce small micro-cracks into the material compound, which in some cases make machining much easier. The diamond tools with the sintered cutting edges or with full-head PCD can offer significant efficiency advantages when subjected to ultrasound. Our diamond cutting tools are diamond-coated or PCD-tipped high-performance tools for processing complex materials.