Inconel 792
Introduction to Inconel 792
Inconel 792 is a precipitation-hardened, cast nickel-based superalloy designed for long-term service at elevated temperatures, particularly in gas turbine and aerospace engine components. Known for its high γ′ content (~65%) and excellent resistance to creep, oxidation, and thermal fatigue, Inconel 792 provides superior structural stability in demanding thermal environments.
The alloy is strengthened through aluminum and titanium additions, which form a stable γ′ phase during aging treatment. Combined with moderate chromium (12–14%) for oxidation resistance and cobalt (9–11%) for thermal fatigue stability, Inconel 792 is ideal for casting and post-machining turbine blades, nozzle guide vanes, and combustor hardware.
Chemical, Physical, and Mechanical Properties of Inconel 792
Inconel 792 (UNS N07792 / AMS 5387) is typically supplied in investment-cast, solution-treated, and age-hardened conditions, optimized for high-temperature aerospace and power generation applications.
Chemical Composition (Typical)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Nickel (Ni) | Balance (~60–63%) | Base matrix, high-temperature strength |
Chromium (Cr) | 12.0–14.0 | Improves oxidation resistance |
Cobalt (Co) | 9.0–11.0 | Enhances fatigue resistance at high temperatures |
Aluminum (Al) | 3.4–4.0 | Forms γ′ precipitates for age-hardening |
Titanium (Ti) | 3.8–4.3 | Strengthens γ′ phase |
Molybdenum (Mo) | 1.5–2.5 | Solid-solution strengthening |
Tungsten (W) | 3.5–4.5 | Enhances creep resistance |
Carbon (C) | 0.10–0.15 | Promotes carbide strengthening at grain boundaries |
Boron (B) | 0.005–0.015 | Improves ductility and hot cracking resistance |
Zirconium (Zr) | ≤0.05 | Grain boundary reinforcement |
Silicon (Si) | ≤0.5 | Assists oxidation resistance |
Manganese (Mn) | ≤0.5 | Enhances casting properties |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 8.10 g/cm³ | ASTM B311 |
Melting Range | 1260–1335°C | ASTM E1268 |
Thermal Conductivity | 10.9 W/m·K at 100°C | ASTM E1225 |
Electrical Resistivity | 1.32 µΩ·m at 20°C | ASTM B193 |
Thermal Expansion | 13.5 µm/m·°C (20–1000°C) | ASTM E228 |
Specific Heat Capacity | 445 J/kg·K at 20°C | ASTM E1269 |
Elastic Modulus | 185 GPa at 20°C | ASTM E111 |
Mechanical Properties (Cast + Aged Condition)
Property | Value (Typical) | Test Standard |
|---|---|---|
Tensile Strength | 880–1020 MPa | ASTM E8/E8M |
Yield Strength (0.2%) | 700–800 MPa | ASTM E8/E8M |
Elongation | ≥3–6% (25mm gauge) | ASTM E8/E8M |
Hardness | 330–400 HB | ASTM E10 |
Creep Rupture Strength | ≥140 MPa @ 870°C, 1000h | ASTM E139 |
Key Characteristics of Inconel 792
High γ′ Volume Fraction: Provides long-term strength retention and creep resistance at 900–1000°C for critical engine components.
Oxidation and Sulfidation Resistance: Chromium and aluminum form protective oxide scales, extending service life in combustion and exhaust environments.
Castability and Structural Reliability: Designed for investment casting of thin-wall, intricate geometries with low porosity and uniform microstructure.
Machinability After Aging: CNC-machined parts maintain dimensional tolerances within ±0.02 mm and Ra ≤ 1.0 µm surface finishes.
CNC Machining Challenges and Solutions for Inconel 792
Machining Challenges
Elevated Hardness and γ′ Strengthening
Age-hardened Inconel 792 (~400 HB) poses significant challenges in tool wear and chip control during CNC milling and turning.
Heat Retention and Built-up Edge
Poor thermal conductivity and high strength lead to localized heating, requiring advanced coolant strategies and sharp edge geometry.
Abrasive Carbides and Intermetallics
Carbide and γ′ phase particles accelerate flank and crater wear on cutting tools without optimized coatings.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | PVD-coated carbide or SiAlON ceramics | Offers high wear resistance and thermal stability |
Coating | AlTiN, AlCrN (3–6 µm) | Minimizes heat transfer and friction |
Geometry | Positive rake (10–12°), edge honed for strength | Reduces cutting force and prevents chipping |
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 | 80–100 |
Finishing | 30–45 | 0.05–0.10 | 0.3–0.8 | 100–150 |
Surface Treatment for Machined Inconel 792 Parts
Hot Isostatic Pressing (HIP)
HIP removes porosity and refines grain structure, boosting fatigue strength and improving dimensional consistency in cast turbine blades and vanes.
Heat Treatment
Heat Treatment typically involves solution treatment at 1170°C followed by aging at ~845°C to maximize γ′ phase distribution and creep resistance.
Superalloy Welding
Superalloy Welding requires low-heat input TIG or EB welding methods due to the alloy’s susceptibility to cracking during rapid solidification.
Thermal Barrier Coating (TBC)
TBC Coating applies 125–250 µm of YSZ ceramics to reduce surface temperatures by up to 200°C, improving oxidation and fatigue resistance.
Electrical Discharge Machining (EDM)
EDM is ideal for producing sharp features and cooling holes with ±0.01 mm accuracy in hardened Inconel 792 parts.
Deep Hole Drilling
Deep Hole Drilling achieves deep, high aspect ratio holes (L/D ≥ 40:1) for cooling channels in vanes and blades.
Material Testing and Analysis
Material Testing includes creep, tensile, hardness, and metallographic validation per AMS 5387 and ASTM E139 standards.
Industry Applications of Inconel 792 Components
Aerospace Turbine Engines
Turbine blades, vanes, and shrouds.
Delivers structural integrity and oxidation resistance above 950°C in high-thrust environments.
Power Generation
Hot-section stators and combustor hardware in gas turbines.
Operates under prolonged thermal and mechanical stress cycles.
Defense & Space Systems
Engine nozzles, hot air ducts, and thermally loaded structural supports.
Resists fatigue, oxidation, and creep under rapid cycling and reentry conditions.
Energy Sector
Stationary gas turbine rotors and blade platforms.
Ideal for base-load operation in combined cycle power plants.
FAQs
What are the benefits of using Inconel 792 for turbine blades over Inconel 738 or 713?
How does Inconel 792 respond to HIP and heat treatment for fatigue enhancement?
What are the recommended CNC strategies for complex geometries in Inconel 792?
Can Neway provide integrated services for casting, EDM, and TBC on Inconel 792?
What standards and certifications are applied for aerospace-grade Inconel 792 parts?
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