Single Crystal Casting IN713LC Gas Turbine Nozzle Ring

Core Technology of IN713LC Single Crystal Nozzle Ring Casting

1. Wax Pattern Fabrication High-precision wax patterns are developed using injection molding, ensuring dimensional tolerances of ±0.05 mm and detailed segment geometry.

2. Shell Mold Assembly Refractory ceramic shells are constructed in multiple layers, achieving structural integrity and thermal shock resistance during casting at >1450°C.

3. Spiral Selector Design A helical grain selector is integrated at the casting base to guide single crystal growth along the [001] axis and eliminate grain boundaries.

4. Vacuum Induction Melting IN713LC is melted under vacuum (≤10⁻³ Pa) using vacuum induction melting, ensuring chemical purity and metallurgical uniformity.

5. Directional Solidification The mold is withdrawn at a controlled rate (~3 mm/min) from the hot zone, creating a monocrystalline structure throughout the nozzle ring arc.

6. Shell Removal and Cleaning Post-casting, ceramic molds are removed using blasting and acid leaching, preserving the precision of cooling slots and attachment features.

7. Hot Isostatic Pressing (HIP) HIP is performed at 1150°C and 150 MPa to eliminate micro-voids and enhance fatigue strength.

8. Heat Treatment Solution treatment at 1200°C followed by aging at 850°C refines the γ' phase through precision heat treatment, improving creep and oxidation resistance.

Material Properties of IN713LC for Nozzle Rings

IN713LC is a nickel-based superalloy with proven performance in high-temperature, high-load turbine applications:

• Max Operating Temperature: 982°C (1800°F)

• Ultimate Tensile Strength: ≥1034 MPa

• Creep Rupture Strength: ≥200 MPa at 760°C for 1000 hrs

• Grain Orientation: Single crystal [001], <2° deviation

• Oxidation Resistance: Excellent under hot gas exposure

• Gamma Prime Strengthening: >50% phase volume fraction

Case Study: IN713LC Single Crystal Nozzle Ring for Gas Turbine

Project Background

Neway AeroTech was tasked with producing a first-stage nozzle ring for a 120 MW industrial gas turbine. The requirement: a creep- and oxidation-resistant ring segment with zero grain boundaries and dimensional tolerance within ±0.05 mm.

Nozzle Ring Applications

• Power Turbines (e.g., GE Frame 7EA): First-stage nozzle rings guide combustion gases through rotating blades, demanding precise flow profiles and thermal stability.

• Aeroengine Turbines (e.g., CFM56): Nozzle rings used in hot gas path sections, where cycle fatigue and oxidation are major concerns.

• Marine Gas Turbines (e.g., LM2500): Operating in corrosive salt-laden atmospheres, nozzle rings must retain geometry and integrity over long cycles.

• Combined Cycle Plants: Nozzle rings that operate continuously in high-efficiency turbines, contributing to optimized fuel usage and emission control.

IN713LC Nozzle Ring Manufacturing Process

1. Wax Pattern Design and Selector Placement Custom-designed wax patterns incorporate spiral selectors for directional solidification control, based on CFD analysis.

2. Vacuum Investment Casting Execution IN713LC alloy is poured in vacuum conditions, and directional withdrawal initiates monocrystalline grain growth through the ring profile.

3. HIP and Thermal Processing After casting, hot isostatic pressing and solution-aging heat treatment improve fatigue life and mechanical uniformity.

4. CNC Machining and EDM Precision holes, bosses, and segment interfaces are finalized via superalloy CNC machining and EDM.

5. Dimensional and Structural Inspection Blades are verified by CMM, X-ray, and metallographic evaluation for orientation and internal soundness.

Manufacturing Challenges

• Preventing stray grain formation in large-diameter ring sections

• Ensuring uniform solidification in asymmetrical arc geometries

• Managing thermal gradients to prevent cracking or hot tears

• Maintaining tight tolerances across mating surfaces post-HIP

Results and Verification

• All nozzle rings confirmed single crystal structure with <2° grain deviation

• Zero internal defects detected after HIP and NDT inspection

• Tensile and creep properties exceeded 1034 MPa and 200 MPa benchmarks

• Dimensional accuracy maintained within ±0.03 mm across 360° ring interface

FAQs

1. Why is single crystal casting used for gas turbine nozzle rings?

2. What is the maximum temperature IN713LC nozzle rings can withstand?

3. How does Neway AeroTech ensure single crystal growth in nozzle rings?

4. What post-processing is required for turbine nozzle rings?

5. Are HIP and X-ray inspections standard for nozzle ring manufacturing?