Engineering ceramics - turbine blades

Engineering ceramics can be made in a wide range of sizes and shapes. The turbine blades shown here are an example of the complex shapes that can now be achieved with the advanced fabrication methods available to the manufacturer. These blades have been manufactured to the high material and dimensional specifications demanded by the aerospace industry.

The blades illustrated are made from silicon nitride (Si ₃N ₄). This ceramic is one of the many high performance ceramic materials available to designers. The material has a number of desirable properties that make it attractive to the aerospace industry:

• low density = 3.2g/cm ³ compared with ~8g/cm ³ for superalloys
• high hardness - 1800kgf/mm compared with 800kgf/mm for steel
• high strength at high temperature - for some grades of Si ₃N ₄ strength decreases only at temperatures in excess of 1200°C.

These properties make Si ₃N ₄ an ideal material for use at high temperatures, in areas where weight is critical and where a high resistance to wear and erosion is required. The joining issues surrounding the location of the ceramic can be addressed using a number of different technologies.