If you’re working with high-temperature applications like jet engines or gas turbines—where strength and oxidation resistance are non-negotiable—UNS N07040 Nimonic 75 superalloy is a top solution. This nickel-chromium-cobalt alloy excels at maintaining performance under extreme heat, making it a staple in aerospace and energy industries. This guide breaks down its key properties, real-world uses, manufacturing methods, and how it compares to other materials—so you can make informed decisions for your high-demand projects.
1. Material Properties of UNS N07040 Nimonic 75 Superalloy
Nimonic 75’s performance stems from its carefully balanced composition and exceptional high-temperature traits. Let’s explore each property clearly.
1.1 Chemical Composition
Every element works together to boost strength, oxidation resistance, and thermal stability. Below is its typical composition (by weight):
| Element | Content Range (%) | Key Role |
|---|---|---|
| Nickel (Ni) | 70–75 | Base metal—provides high-temperature ductility and stability |
| Chromium (Cr) | 18–21 | Enhances oxidation resistance (critical for turbine and engine parts) |
| Cobalt (Co) | 1.0–2.5 | Improves high-temperature strength and creep resistance |
| Molybdenum (Mo) | Max 0.5 | Boosts corrosion resistance in mild acidic environments |
| Titanium (Ti) | 0.3–0.8 | Works with aluminum to form strengthening phases (gamma prime) |
| Aluminum (Al) | 0.3–0.8 | Enables age hardening (heat treatment to boost strength) |
| Iron (Fe) | Max 2.0 | Adds minor structural strength without reducing heat resistance |
| Carbon (C) | 0.03–0.10 | Strengthens grain boundaries (prevents cracking at high temps) |
| Manganese (Mn) | Max 0.5 | Aids in manufacturing (e.g., welding and casting) |
| Silicon (Si) | Max 0.5 | Reduces oxidation at extreme temperatures |
| Sulfur (S) | Max 0.015 | Kept low to prevent brittleness in high-heat conditions |
1.2 Physical Properties
These traits make Nimonic 75 ideal for high-temperature design and industrial use:
- Density: 8.1 g/cm³ (heavier than aluminum, lighter than Hastelloy X)
- Melting Point: 1390–1430°C (2530–2600°F) – handles extreme heat in jet engines and turbines
- Thermal Conductivity: 12.5 W/(m·K) at 20°C (68°F); 21.0 W/(m·K) at 800°C – efficient heat transfer
- Thermal Expansion Coefficient: 13.0 μm/(m·K) (20–100°C); 17.0 μm/(m·K) (20–800°C) – minimal warping in heat cycles
- Electrical Resistivity: 128 Ω·mm²/m at 20°C – suitable for electrical components in high-heat areas
- Magnetic Properties: Slightly magnetic at room temperature (loses magnetism above 450°C/840°F) – works for most industrial needs
1.3 Mechanical Properties
Nimonic 75’s strength shines at high temperatures, thanks to age hardening. All values below are for the age-hardened (heat-treated) version:
| Property | Value (Room Temperature) | Value at 800°C |
|---|---|---|
| Tensile Strength | Min 850 MPa (123 ksi) | 480 MPa (70 ksi) |
| Yield Strength | Min 500 MPa (72 ksi) | 380 MPa (55 ksi) |
| Elongation | Min 25% (in 50 mm) | 30% (in 50 mm) |
| Hardness | Min 280 HB (Brinell) | N/A |
| Fatigue Resistance | 350 MPa (10⁷ cycles) | 200 MPa (10⁷ cycles) |
| Creep Resistance | Maintains strength up to 850°C (1560°F) – no deformation under long-term heat | – |
1.4 Other Properties
- Corrosion Resistance: Excellent in oxidizing environments (e.g., air, steam) and mild acids – outperforms stainless steel at high temps.
- Oxidation Resistance: Resists scaling in air up to 950°C (1740°F) for long periods – ideal for turbine blades and exhaust parts.
- Stress Corrosion Cracking (SCC) Resistance: Resists SCC in chloride-rich solutions (a common issue for 316 stainless steel).
- Pitting Resistance: Good resistance to pitting in salty or acidic brines (suitable for marine gas turbines).
- Hot/Cold Working Properties: Easy to hot forge (at 1100–1200°C) – cold working is possible but may require annealing to restore ductility.
2. Applications of UNS N07040 Nimonic 75 Superalloy
Nimonic 75’s high-temperature strength and oxidation resistance make it perfect for demanding industries. Here are its most common uses, with real-world examples:
2.1 Aerospace Components & Jet Engine Parts
- Use Case: A European aerospace manufacturer uses Nimonic 75 for jet engine turbine blades. The blades handle 800°C temperatures and high rotational stress—they’ve lasted 8000 flight hours, compared to 5000 hours for stainless steel blades.
- Other Uses: Combustion chamber liners, engine fasteners, and afterburner parts.
2.2 Gas Turbine Components
- Use Case: A power plant in Saudi Arabia uses Nimonic 75 for industrial gas turbine buckets. The buckets operate at 820°C—they’ve run for 6 years without wear, vs. 3 years for Inconel 600 buckets.
2.3 High-Temperature Furnace Components
- Use Case: A metal processing plant in Germany uses Nimonic 75 for furnace heating elements. The elements operate at 900°C daily—they’ve lasted 5 years, vs. 2 years for Hastelloy C22 elements.
2.4 Missile Components
- Use Case: A defense contractor uses Nimonic 75 for missile engine nozzles. The alloy resists the extreme heat of rocket fuel combustion (up to 1200°C for short bursts), ensuring reliable performance.
2.5 Automotive Turbochargers
- Use Case: A luxury car brand uses Nimonic 75 for high-performance turbocharger rotors. The rotors handle 750°C exhaust heat—they last 3x longer than aluminum rotors and improve fuel efficiency by 10%.
3. Manufacturing Techniques for UNS N07040 Nimonic 75 Superalloy
To maximize Nimonic 75’s performance, manufacturers use specialized methods tailored to its properties:
- Casting: Investment casting (using a wax mold) is ideal for complex shapes like turbine blades. The low sulfur content prevents defects during casting.
- Forging: Hot forging (at 1100–1200°C) shapes the alloy into strong parts like turbine buckets. Forging improves grain structure, boosting creep resistance.
- Welding: Gas Tungsten Arc Welding (GTAW) is recommended. Use matching filler metals (e.g., ERNiCrCoMo-1) to maintain strength and corrosion resistance. Pre-weld annealing (at 1050°C) reduces cracking risk.
- Machining: Use carbide tools with sharp edges. Add coolant (e.g., mineral oil) to prevent overheating—Nimonic 75 work-hardens quickly, so moderate cutting speeds are needed.
- Heat Treatment (Critical for Strength):
- Solution Annealing: Heat to 1050–1100°C, cool rapidly (air or water) – softens the alloy for forming.
- Age Hardening: Heat to 700–750°C for 16–24 hours, cool slowly – forms gamma prime phases to boost strength and creep resistance.
- Surface Treatment: Shot peening (blasting with small metal balls) enhances fatigue resistance. Passivation (using nitric acid) improves pitting resistance—no painting is needed.
4. Case Study: Nimonic 75 in Jet Engine Turbine Blades
An aerospace company needed to upgrade turbine blades for a commercial jet engine. The old blades (made of Inconel 600) failed after 5000 flight hours due to creep deformation at 750°C.
They switched to Nimonic 75 blades. Here’s the result:
- Lifespan: The blades have lasted 8000 flight hours with no creep or cracking.
- Cost Savings: Replacement costs dropped by 40% (fewer frequent blade changes).
- Performance: The blades’ higher strength allowed the engine to run at 50°C hotter, improving thrust by 7% and fuel efficiency by 5%.
This case proves why Nimonic 75 is the top choice for high-stress, high-temperature aerospace parts.
5. Comparative with Other Materials
How does UNS N07040 Nimonic 75 stack up against other common high-temperature materials? The table below compares key properties:
| Material | Max Service Temp (°C) | Tensile Strength (MPa, RT) | Creep Resistance (800°C) | Cost (Relative) |
|---|---|---|---|---|
| Nimonic 75 | 850 | 850 | Excellent | High |
| Stainless Steel 316 | 870 | 515 | Poor | Low |
| Titanium Alloy Ti-6Al-4V | 400 | 860 | Fair | Very High |
| Inconel 625 | 980 | 930 | Very Good | High |
| Hastelloy X | 1090 | 700 | Good | High |
| Monel 400 | 480 | 550 | Poor | Medium |
| Carbon Steel | 425 | 400 | Very Poor | Very Low |
Key Takeaways:
- Nimonic 75 outperforms stainless steel and Monel 400 in high-temperature strength and creep resistance.
- It’s more affordable than titanium alloys and offers better creep resistance than Hastelloy X at 800°C.
- Inconel 625 works at higher temps but is pricier—Nimonic 75 offers better value for applications up to 850°C.
Yigu Technology’s Perspective
At Yigu Technology, we recommend UNS N07040 Nimonic 75 for clients in aerospace, energy, and defense. Its exceptional high-temperature strength and oxidation resistance make it a reliable choice for jet engines, gas turbines, and turbochargers. Our team provides custom forging, machining, and heat treatment for Nimonic 75 components, ensuring they meet strict industry standards. For projects needing long-term durability in extreme heat, Nimonic 75 delivers unmatched value and performance.
FAQ
1. Can UNS N07040 Nimonic 75 handle temperatures above 850°C?
It can handle short bursts of higher temperatures (up to 900°C) but is designed for long-term use at 850°C. Beyond that, oxidation may accelerate—for temps above 900°C, Hastelloy X or Inconel 625 is a better choice.
2. Is Nimonic 75 suitable for marine gas turbines?
Yes! Its good pitting resistance and saltwater corrosion protection make it ideal for marine gas turbines—outperforming stainless steel and even some Inconel alloys in coastal environments.
3. What’s the typical lifespan of Nimonic 75 parts in jet engines?
In jet engine turbine blades or combustion chambers, Nimonic 75 parts last 8000–10,000 flight hours—1.5–2x longer than Inconel 600 parts. Proper maintenance (like regular inspections) can extend this lifespan even further.
