Inconel 713C
Introduction to Inconel 713C
Inconel 713C is a high-strength, precipitation-hardenable cast nickel-chromium superalloy optimized for service in extreme thermal and mechanical conditions. Its combination of excellent creep resistance, oxidation protection, and castability makes it particularly suitable for turbine blades, hot gas path components, and structural engine parts operating continuously above 950°C (1742°F).
Engineered with a base of nickel (~75%) and alloyed with chromium (12–14%), aluminum (5.5–6.5%), molybdenum (4–5%), and niobium (1.5–2.5%), Inconel 713C achieves a fine γ′ precipitate structure and stable mechanical behavior under thermal fatigue. It is an evolution of the standard Inconel 713 alloy, enhanced to offer better cast fluidity and slightly improved hot-corrosion performance.
Chemical, Physical, and Mechanical Properties of Inconel 713C
Inconel 713C (UNS N07713C / AMS 5381) is primarily used in cast and aged form for high-performance aerospace and energy components. It conforms to standards such as AMS 5381 and MIL-C-24707.
Chemical Composition (AMS 5381)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Nickel (Ni) | Balance (~75.0%) | Matrix metal for thermal stability |
Chromium (Cr) | 12.0–14.0 | Oxidation and hot corrosion resistance |
Aluminum (Al) | 5.5–6.5 | Promotes γ′ phase strengthening |
Molybdenum (Mo) | 4.0–5.0 | Enhances creep rupture resistance |
Niobium (Nb) | 1.5–2.5 | Strengthens via NbC formation and γ″ |
Titanium (Ti) | 0.6–1.2 | γ′ phase stability |
Carbon (C) | 0.10–0.20 | Forms carbides for high-temperature strength |
Zirconium (Zr) | 0.05–0.15 | Improves grain boundary cohesion |
Boron (B) | 0.005–0.015 | Enhances hot strength and ductility |
Iron (Fe) | ≤3.0 | Residual element |
Silicon (Si) | ≤0.50 | Minimizes oxidation scaling |
Manganese (Mn) | ≤0.50 | Aids in castability |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 8.01 g/cm³ | ASTM B311 |
Melting Range | 1250–1330°C | ASTM E1268 |
Thermal Conductivity | 11.0 W/m·K at 100°C | ASTM E1225 |
Electrical Resistivity | 1.22 µΩ·m at 20°C | ASTM B193 |
Thermal Expansion | 13.8 µm/m·°C (20–1000°C) | ASTM E228 |
Specific Heat Capacity | 455 J/kg·K at 20°C | ASTM E1269 |
Elastic Modulus | 197 GPa at 20°C | ASTM E111 |
Mechanical Properties (Aged Cast Condition)
Property | Value (Typical) | Test Standard |
|---|---|---|
Tensile Strength | 940–1060 MPa | ASTM E8/E8M |
Yield Strength (0.2%) | 610–740 MPa | ASTM E8/E8M |
Elongation | ≥3–5% (25mm gauge) | ASTM E8/E8M |
Hardness | 330–390 HB | ASTM E10 |
Creep Rupture Strength | ≥160 MPa @ 871°C, 100h | ASTM E139 |
Key Characteristics of Inconel 713C
Elevated Temperature Strength: Retains tensile strength above 940 MPa and demonstrates sustained creep resistance >150 MPa at 871°C, making it ideal for rotating and static hot section parts.
Oxidation and Hot Gas Resistance: Cr-Al oxide layers protect against surface degradation in turbine environments up to 1000°C, even under fluctuating thermal loads.
Gamma Prime Reinforcement: High γ′ volume fraction (~60%) increases hardness and maintains shape integrity in demanding service cycles.
Castability and Dimensional Stability: Designed for investment casting with excellent fluidity, then post-machined to tight tolerances (±0.02 mm) and low surface roughness (Ra ≤ 0.8 µm).
CNC Machining Challenges and Solutions for Inconel 713C
Machining Challenges
High Hardness and Tool Wear
Post-aged castings measure up to 390 HB, which accelerates wear on carbide inserts and causes flank chipping.
Low Ductility and Brittleness
Elongation is limited (~3–5%), increasing risk of surface cracking or edge deformation during finishing passes.
Thermal Load Concentration
Poor thermal conductivity leads to rapid heat buildup at the tool-chip interface, causing crater wear and dimensional drift.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | SiAlON ceramic or coated carbide (CBN for finishing) | High resistance to heat and wear |
Coating | TiAlN/AlCrN, 3–6 µm PVD | Minimizes diffusion wear and oxidation |
Geometry | Positive rake (10–12°), reinforced edge | Enhances tool life and surface control |
Cutting Parameters (ISO 3685)
Operation | Speed (m/min) | Feed (mm/rev) | DOC (mm) | Coolant Pressure (bar) |
|---|---|---|---|---|
Roughing | 15–25 | 0.20–0.30 | 2.0–3.0 | 80–120 |
Finishing | 30–45 | 0.05–0.10 | 0.3–0.8 | 100–150 |
Surface Treatment for Machined Inconel 713C Parts
Hot Isostatic Pressing (HIP)
HIP removes shrinkage porosity and improves fatigue strength by over 25%, enhancing structural performance in cyclic high-temperature service.
Heat Treatment
Heat Treatment involves solutionizing at 1150–1175°C and aging to optimize γ′ distribution and tensile properties across large cast sections.
Superalloy Welding
Superalloy Welding uses GTAW or EBW with matching fillers to minimize HAZ embrittlement and maintain structural integrity under thermal cycling.
Thermal Barrier Coating (TBC)
TBC Coating applies 100–300 µm YSZ layers via APS or EB-PVD, reducing surface temperatures by up to 200°C for extended turbine part life.
Electrical Discharge Machining (EDM)
EDM supports complex internal geometries and slots in hardened Inconel 713C castings with ±0.01 mm accuracy.
Deep Hole Drilling
Deep Hole Drilling achieves L/D ratios ≥40:1 for cooling holes and air passages in turbine segments.
Material Testing and Analysis
Material Testing covers ultrasonic, X-ray, and grain structure analysis (ASTM E112, AMS 2175) to certify integrity in safety-critical parts.
Industry Applications of Inconel 713C Components
Aerospace and Aviation
Turbine blades, nozzle guide vanes, and combustion support structures.
Operates reliably in hostile environments with cyclic thermal and centrifugal loads.
Industrial Gas Turbines
First-stage nozzles, buckets, and shrouds.
Long-term exposure to 950–1000°C gas streams without creep or oxidation degradation.
Marine Propulsion
Turbocharger rotors and high-speed exhaust housings.
Handles thermal gradients and salt-induced hot corrosion effectively.
Automotive Performance
High-performance turbocharger wheels and inlet components.
Maintains dimensional integrity under extreme temperature fluctuations.
FAQs
What are the best cutting tools and speeds for CNC machining Inconel 713C castings?
How does Inconel 713C compare with Inconel 713 in oxidation and hot corrosion resistance?
What surface treatments improve fatigue and thermal resistance in Inconel 713C?
Can Neway provide both HIP and EDM for precision Inconel 713C turbine parts?
What quality control tests are used to validate Inconel 713C components for aerospace use?
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