Superalloy Turbine Blades Free Forging Service

Core Technology of Superalloy Free Forging

1. Billet Preparation and Heating Superalloy ingots are cut to size and uniformly heated to forging temperatures between 1050–1180°C in inert or vacuum furnaces to prevent oxidation.

2. Open Die Forging Operations Using programmable hydraulic presses (up to 5000 tons), material is shaped between flat or contoured dies without enclosed tooling, ensuring flexibility and directional grain flow.

3. Grain Refinement and Flow Control Forging schedules and strain rates are engineered to promote fine equiaxed grains (<100 μm) or flow-aligned grains depending on blade stress orientation.

4. Intermediate Heat Treatments Solution treatment and controlled cooling are applied after forging to homogenize the microstructure and relieve residual stresses.

5. Precision CNC Machining Final blade geometry is achieved through 5-axis CNC machining, meeting tolerances as tight as ±0.02 mm and aerodynamic surface finishes (Ra ≤0.8 μm).

6. EDM for Cooling Features Electrical Discharge Machining (EDM) is employed to cut complex internal cooling channels and blade root contours with high precision.

7. Post-Processing and Inspection Hot isostatic pressing (HIP), thermal barrier coating (TBC), and ultrasonic or X-ray inspection ensure fatigue resistance and defect-free integrity.

Suitable Superalloys for Free Forged Turbine Blades

Applications in Aerospace and Energy Sectors

• Aircraft Engine Turbine Blades Require directionally forged grain structures to withstand rotational stresses and temperature gradients during takeoff and cruise cycles.

• Industrial Gas Turbine Blades Used in continuous-duty turbines for power generation, requiring prolonged high-temperature fatigue resistance and oxidation stability.

• Turboprop Blade Cores Forged as preforms before precision machining and coating, ensuring mechanical integrity and mass balance.

• Compressor and Stator Blades Forged parts must maintain low cycle fatigue (LCF) resistance while being lightweight and dimensionally stable.

Case Study: Free Forging of Inconel 718 Turbine Blades

Objective

To produce forged Inconel 718 turbine blade blanks for a commercial jet engine program, targeting grain refinement, tight dimensional control, and zero internal defects.

Process Summary

• Billet Preheating: 1150°C ±5°C in protective atmosphere

• Open-Die Forging: 3-pass reduction forging under 2000-ton press

• Grain Size Achieved: ASTM 6–8 (≤20 μm) with aligned flow lines

• HIP and Aging Treatment: 1180°C HIP followed by 720°C aging

• CNC Machining: ±0.02 mm tolerance across all aerodynamic surfaces

• Inspection: 100% X-ray and ultrasonic for inclusion-free qualification

Results

• Tensile Strength: ≥1240 MPa at room temp

• Elongation: ≥20%

• Fatigue Life: >100,000 cycles at 650°C

• Dimensional Consistency: ±0.015 mm achieved across 50+ blades

FAQs

1. What are the advantages of free forging over closed-die forging for turbine blades?

2. Which superalloys are best suited for forged turbine blades?

3. How does forging improve grain flow and fatigue resistance in turbine components?

4. What inspection techniques are used to verify forged blade quality?

5. Can complex blade cooling structures be integrated after forging?