Silicon nitride: a fascinating variety of properties

Technical progress depends on materials that allow the manufacture of powerful components and systems. Silicon nitride (Si₃N₄) is one such a material. The high-performance ceramic features a combination of exceptional properties but also imposes high requirements on the manufacturing process. Sembach specializes in ceramics and is currently expanding its machinery to allow large-batch components of sintered silicon nitride (SSN) to be produced economically.

Silicon nitride is a high-performance ceramic with the formula Si₃N₄ and belongs to the group of non-oxide ceramics that are generally characterized by exceptional technological properties. Si₃N₄ is a highly resistant material used in lightweight construction and high-temperature applications. It is an ideal option for components previously made of steel, when high temperature stability combined with low weight, resistance to corrosive influences as well as abrasion resistance are required. Si₃N₄ is a rather “new” material because it was only developed for industrial use during the second half of the last century. At that time, it was necessary to find an alternative to metallic materials used in turbines or combustion engines exposed to mechanical and thermal stresses that would allow higher operating temperatures and increased efficiency. High requirements imposed on processing i.e. production of powdered raw materials, shaping, sintering and high cost, are the reasons that the material has mostly been used for specific applications until now.

Technological properties and fields of application

With a low density of 3.2 to 3.3 g/cm³, silicon nitride is almost as light as the light metal aluminum with 2.7 g/cm³ and a bending strength of up to 1,000 MPa. In addition, Si₃N₄ is characterized by high resistance to wear and exceeds high-temperature properties of most metals such as high-temperature strength and creep resistance. Other features are its low coefficient of thermal expansion resulting in very high thermal shock resistance as well as high fracture toughness (7 MPam^1/2). Therefore, workpieces made of Si₃N₄ are insensitive to shocks and impacts. These workpieces withstand operating temperatures up to 1,300° C and are resistant to corrosive effects and chemicals such as acids and alkaline solutions or special molten metals such as aluminum.

All these properties make silicon nitride ideal for use with components exhibiting high mechanical strength even when exposed to sudden stresses and showing consistent resistance to high operational temperatures, corrosive media and heavy wear. Application examples are components for combustion engines, power plants and other energy or chemical-technical systems, all types of sealings and bearings exposed to high stresses, pump impellers used for aggressive media, guides for leading components such as wires, fibers and threads as well as cutting tools for materials difficult to machine. It is remarkable that these processes can be carried out at highest speeds without the use of cooling lubricants. Other application examples are tools used in sheet metal forming and foundry technology allowing considerably enhanced service lives in contrast to steel components.

Sembach: specialist expertise in process technology and manufacturing equipment

Sembach specializes in ceramics and has gained extensive experience in the construction, shaping and manufacture of workpieces made of high-performance ceramics over the course of many decades. Modern and well-equipped production facilities allow Sembach to efficiently manufacture complex shaped prototypes and large-batch components of silicon nitride (SSN) using injection molding, dry pressing and 5-axis milling. Sembach is ready to participate in the development and opening up of new applications for silicon nitride, a high class, high-performance ceramic material thanks to its varied properties.