Superalloys in vacuum investment casting
Vacuum investment casting is casting in an airless, closed or air-gas thinned space under low pressure.
The material is melted and the melt is cast under vacuum. This takes place in a high-tech two-chamber casting system. All this is made possible by specially developed gas-permeable ceramic shells.
Advantages of vacuum investment casting:
- No danger of oxidation during casting of alloys with oxygen-affinitive elements such as titanium and aluminium.
- Some materials, such as nickel-based alloys, can only be cast under vacuum because in liquid state they would react with oxygen
- Especially thin wall thicknesses can be achieved with this process
- Application at temperatures of up to 1,000oC
- Improved corrosion and acid resistance even with the most aggressive media
- High degree of purity in the microstructure (low level of non-metallic inclusions)
- All other advantages of the investment casting process remain
Examples of materials used in the vacuum process
| Nimonic 80A, 2,4952, Ni-Basis Chemically resistant and highly heat-resisting components, aviation and space travel |
| Nimonic 90, 2.4632, Ni-Basis Chemically resistant and highly heat-resisting components, aviation and space travel, automobile industry |
| INCO 713C, 2.3671, Ni-Basis Chemically resistant and highly heat-resisting components, aviation and space travel, automobile industry |
Application example:
Adherence to ever stricter emission standards is binding for the automobile industry. One way of reducing emissions is increasing the temperature in the engine and hence also in the turbocharger.
In this application, conventional heat-resistant stainless steel alloys reach their limit, and have largely been replaced by special alloys.
These parts must not only be resistant to the chemical elements in the exhaust gases, they must also have very high creep rupture strengths at extreme temperatures.
