Precision casting impellers are turbine components manufactured through precision casting processes (such as investment casting, ceramic mold casting, etc.), widely used in aerospace, energy, chemical, and other industries. Below is a detailed introduction to precision casting impellers:
1. Precision Casting Processes
- Investment Casting (Lost-Wax Casting):
- Process: Wax pattern creation → Wax tree assembly → Multi-layer ceramic slurry coating → Dewaxing → High-temperature sintering → Metal pouring → Post-casting cleanup.
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Advantages: Capable of producing impellers with complex geometries, high surface finish (Ra 1.66.3μm), and tight dimensional tolerances (CT46).
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Other Processes: Ceramic mold casting, silica sol casting, etc., suitable for different materials or precision requirements.
2. Material Selection
- High-Temperature Alloys: Inconel 718 (jet engines), Hastelloy X (corrosion resistance).
- Stainless Steel: 304, 316L (chemical pumps, desalination).
- Titanium Alloys: Ti-6Al-4V (lightweight, high strength, corrosion resistance).
- Aluminum Alloys: A356 (lightweight, cost-sensitive applications).
3. Design Considerations
- Blade Profile: Must comply with fluid dynamics to minimize cavitation and turbulence.
- Uniform Wall Thickness: Avoids casting defects (shrinkage, cracks), typically ≥3mm.
- Balance Requirements: High dynamic balance standards (e.g., G2.5 grade) to prevent vibration at high speeds.
- Post-Processing: CNC machining (shaft holes, end faces), surface strengthening (shot peening, nitriding).
4.Quality Control
- Non-Destructive Testing (NDT): X-ray (internal defects), fluorescent penetrant inspection (surface cracks).
- Dimensional Inspection: CMM (blade contour, mounting holes).
- Performance Testing: Dynamic balance testing, hydrostatic pressure testing (leak-proof sealing).
5. Applications
- Aerospace: Compressor impellers, fuel pump impellers.
- Energy: Gas turbine blades, nuclear pump impellers.
- Chemical Industry: Centrifugal pump impellers (acid-resistant designs).
- Automotive: Turbocharger wheels (aluminum/nickel-based alloys).
6. Common Issues & Solutions
- Defects: Porosity, slag inclusions → Optimize gating system and melting process.
- Deformation: Control cooling rate, use fixtures for shaping.
- Insufficient Performance: Adjust mechanical properties via heat treatment (e.g., solution + aging).