Inconel 713
Introduction to Inconel 713
Inconel 713 is a precipitation-hardenable nickel-based casting superalloy designed for excellent strength, thermal fatigue resistance, and oxidation stability at elevated temperatures up to 980°C (1800°F). Originally developed for structural components in turbine engines, this alloy is widely utilized in aerospace, energy, and industrial gas turbine applications requiring prolonged high-temperature exposure and mechanical durability.
Composed primarily of nickel (≥75%), with additions of chromium (12–14%), aluminum (5.5–6.5%), molybdenum (4–5%), and niobium (1.5–2.5%), Inconel 713 delivers outstanding creep rupture strength and maintains microstructural integrity under extreme service conditions. Its castable nature allows for net-shape designs, but precision CNC machining is often required to meet final dimensional and surface requirements.
Chemical, Physical, and Mechanical Properties of Inconel 713
Inconel 713 (UNS N07713 / AMS 5380) is typically supplied in the investment cast and aged condition and adheres to specifications for aerospace-grade high-temperature components.
Chemical Composition (AMS 5380)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Nickel (Ni) | Balance (~75.0%) | Base metal; thermal stability and strength |
Chromium (Cr) | 12.0–14.0 | Provides oxidation and hot corrosion resistance |
Aluminum (Al) | 5.5–6.5 | Strengthens via γ′ (Ni₃Al) precipitation |
Molybdenum (Mo) | 4.0–5.0 | Enhances creep resistance |
Niobium (Nb) | 1.5–2.5 | Precipitates hardening phases (NbC, γ″) |
Titanium (Ti) | 0.6–1.2 | Strengthens γ′ phase |
Carbon (C) | 0.10–0.20 | Forms carbides for creep strength |
Zirconium (Zr) | 0.05–0.15 | Improves grain boundary strength |
Boron (B) | 0.005–0.015 | Enhances grain boundary cohesion |
Iron (Fe) | ≤3.0 | Minor alloying element |
Silicon (Si) | ≤0.50 | Controlled to limit oxidation |
Manganese (Mn) | ≤0.50 | Improves castability |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 8.00 g/cm³ | ASTM B311 |
Melting Range | 1250–1330°C | ASTM E1268 (DTA) |
Thermal Conductivity | 11.5 W/m·K at 100°C | ASTM E1225 |
Electrical Resistivity | 1.20 µΩ·m at 20°C | ASTM B193 |
Thermal Expansion | 13.9 µm/m·°C (20–1000°C) | ASTM E228 |
Specific Heat Capacity | 460 J/kg·K at 20°C | ASTM E1269 |
Elastic Modulus | 198 GPa at 20°C | ASTM E111 |
Mechanical Properties (Aged Cast Condition)
Property | Value (Typical) | Test Standard |
|---|---|---|
Tensile Strength | 950–1080 MPa | ASTM E8/E8M |
Yield Strength (0.2%) | 620–750 MPa | ASTM E8/E8M |
Elongation | ≥3–6% (25mm gauge) | ASTM E8/E8M |
Hardness | 330–390 HB | ASTM E10 |
Creep Rupture Strength | ≥165 MPa @ 871°C, 100h | ASTM E139 |
Key Characteristics of Inconel 713
High-Temperature Strength: Retains tensile strength above 900 MPa and creep resistance exceeding 150 MPa at 870°C for 100+ hours—ideal for hot-section gas turbine components.
Oxidation and Hot Corrosion Resistance: Chromium and aluminum form stable, protective oxides (Cr₂O₃, Al₂O₃), ensuring resistance up to 1000°C in oxidizing and sulfating environments.
Gamma Prime Strengthening: γ′ volume fraction ~60% contributes to yield strength >700 MPa and excellent dimensional stability at high stress and temperature.
Castability with Precision Machining: Suitable for net-shape investment casting with supplemental CNC finishing to meet ±0.02 mm tolerances and Ra ≤ 0.8 µm surface finishes.
CNC Machining Challenges and Solutions for Inconel 713
Machining Challenges
High Hardness and Abrasiveness
Cast and aged condition yield Brinell hardness up to 390 HB, leading to flank wear and crater damage on carbide tools.
Thermal Sensitivity
Low thermal conductivity (11.5 W/m·K) causes tool tip temperatures to exceed 1000°C, producing rapid oxidation and notch wear.
Workpiece Brittleness
Limited ductility (elongation 3–6%) increases rthe isk of microcracks and edge chipping during aggressive cuts or vibration.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | CBN or ceramic tools (SiAlON, whisker-reinforced) | High red hardness and thermal shock resistance |
Coating | TiAlN or AlCrN PVD, 3–6 µm | Reduces diffusion wear and friction |
Geometry | Positive rake (10–12°), honed or chamfered edge | Improves tool life and surface quality |
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 713 Parts
Hot Isostatic Pressing (HIP)
HIP eliminates internal shrinkage porosity and enhances fatigue strength by >25%, critical for turbine blades and structural castings exposed to cyclic loads.
Heat Treatment
Heat Treatment includes solution heat treatment at 1160°C and aging at 845°C to optimize γ′ precipitation and improve tensile and rupture properties.
Superalloy Welding
Superalloy Welding employs preheated TIG or electron beam welding techniques with Ni-Cr-based fillers to maintain weld integrity under thermal cycling.
Thermal Barrier Coating (TBC)
TBC Coating applies 150–250 µm ceramic zirconia layers to reduce surface temperature by up to 200°C, extending the fatigue life of hot-section parts.
Electrical Discharge Machining (EDM)
EDM enables precise geometry formation in hardened Inconel 713 with ±0.01 mm accuracy, suitable for fir tree slots and cooling holes.
Deep Hole Drilling
Deep Hole Drilling supports high aspect ratio hole machining (L/D ≥ 40:1), vital for blade cooling passages and combustion liner perforations.
Material Testing and Analysis
Material Testing includes macro/microstructure evaluation, X-ray, and ultrasonic inspection per AMS 2175 to validate structural soundness and dimensional precision.
Industry Applications of Inconel 713 Components
Aerospace Turbines
First-stage turbine blades, nozzles, and vanes.
Sustains high thermal gradients and centrifugal loads without creep deformation.
Power Generation
Stationary gas turbine components and nozzle segments.
Excellent oxidation resistance under steady and cyclic thermal loads.
Industrial Heating Systems
Combustor liners, burner tips, and flue gas nozzles.
Maintains strength and corrosion resistance in high-velocity, high-temperature flows.
Automotive Turbochargers
Turbine rotors and housing components.
Withstands thermal shock and oxidation in rapid acceleration-deceleration cycles.
FAQs
What tooling strategies improve surface finish and tool life when machining Inconel 713?
How does Inconel 713 compare with Inconel 738 or 718 regarding creep resistance?
What post-processing is essential after CNC machining Inconel 713 cast parts?
Can Neway apply HIP and TBC in-house for Inconel 713 turbine components?
How is material integrity verified for Inconel 713 aerospace castings?
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