Why investment casting
Turbine and boiler hardware needs sound sections in creep-resistant steels; controlled feeding and volumetric testing make investment casting a dependable route.
Components
- Turbine blades and vanes
- Seal segments
- Hydro runner components
- Fuel nozzles
Materials
Nickel and cobalt superalloys, 13Cr-4Ni martensitic steel, 12 % Cr steels.
Frequently used alloys
| Grade | Type | Standard |
|---|---|---|
| HK | 25Cr-20Ni heat-resistant steel HK40 | ASTM A297/A297M |
| WC9 | 2¼Cr-1Mo steel for high-temperature pressure parts | ASTM A217/A217M |
| G17CrMo9-10 (1.7379) | 2¼Cr-1Mo steel for high-temperature pressure parts | EN 10213 |
| CA6NM | 13Cr-4Ni low-carbon martensitic stainless steel 13-4 type (F6NM) | ASTM A743/A743M, A487/A487M |
Typical requirements
Creep, fatigue and erosion; hot-section parts usually require vacuum casting and extensive NDT.
- Radiographic soundness
- Creep-resistant material grades
- Documented heat treatment
Related engineering topics
Non-destructive testing
NDT methods for investment castings: liquid penetrant, magnetic particle, radiographic and ultrasonic testing, computed tomography, leak testing, personnel qualification and acceptance levels.
Material testing
Verification of cast alloys: spectrometric chemical analysis, PMI, tensile, hardness and impact testing, metallography, ferrite measurement, corrosion tests and heat-treatment verification.
Gating and feeding
How gating systems are designed for investment castings: filling without turbulence, directional solidification, feeding of shrinkage and the influence of cooling rate.