Mastering the hot workability of Nimonic 75 and 80A is crucial between creating high-quality aerospace components and ending up as scrap metal. These high-temperature alloys are extremely sensitive to temperature fluctuations. Our technical guide provides the necessary heating ranges and forging processes to prevent grain coarsening and hot cracking. As a leading nickel alloy manufacturer, Gnee Steel offers VIM + ESR melted bars with superior forging properties and structural uniformity to meet your most demanding project requirements.
Guide to Hot Working and Forging of Nimonic 75 and 80A High-Temperature Alloys
Guide to Hot Working and Forging of Nimonic 75 and 80A High-Temperature Alloys
This guide outlines the hot working and forging processes for two nickel-chromium-based superalloys widely used in aerospace and turbine engineering-Nimonic 75 and Nimonic 80A. Nimonic 75 is a solid solution-strengthened alloy with excellent corrosion resistance and moderate strength; while Nimonic 80A is a precipitation-strengthened alloy with superior creep rupture strength.
How machinable is NIMONIC 75?
Nimonic 75 is a nickel-based heat-resistant superalloy (HRSA) material with a machinability grade of 17% and a hardness of 90 HRB.
1. Chemical Composition: Nimonic 75 vs Nimonic 80A
| Element | Nimonic 75 Content (%) | Nimonic 80A Content (%) |
|---|---|---|
| Nickel (Ni) | Balance (≥ 73.0) | Balance (≥ 65.0) |
| Chromium (Cr) | 18.0 – 21.0 | 18.0 – 21.0 |
| Titanium (Ti) | 0.2 – 0.6 | 1.8 – 2.7 |
| Aluminum (Al) | 0.1 – 0.2 | 1.0 – 1.8 |
| Carbon (C) | 0.08 – 0.15 | 0.10 max |
| Silicon (Si) | ≤ 1.0 | ≤ 1.0 |
| Manganese (Mn) | ≤ 1.0 | ≤ 1.0 |
| Iron (Fe) | ≤ 5.0 | ≤ 3.0 |
| Copper (Cu) | ≤ 0.5 | ≤ 0.2 |
| Sulfur (S) | ≤ 0.015 | ≤ 0.015 |
| Cobalt (Co) | – | ≤ 2.0 |
| Boron (B) | – | ≤ 0.008 |
| Zirconium (Zr) | – | ≤ 0.15 |
Click to download the GH3030 alloy PDF file now
2. Comparison of mechanical properties between Nimonic 75 and Nimonic 80A
| Property | Nimonic 75 (Annealed) | Nimonic 80A (Solution Treated + Aged) |
|---|---|---|
| Tensile Strength, Ultimate (Room Temp) | 650 – 750 MPa | 1000 – 1250 MPa |
| Tensile Strength, Yield (0.2% Offset) (Room Temp) | 300 – 450 MPa | 620 – 850 MPa |
| Elongation at Break (Room Temp) | 30 – 40% | 20 – 30% |
| Hardness, Rockwell C (HRC) | 15 – 25 | 28 – 38 |
| Hardness, Brinell (HB) | 150 – 200 | 280 – 350 |
| Modulus of Elasticity (Young's Modulus) | 211 GPa | 211 GPa |
| Poisson's Ratio | 0.30 | 0.30 |
| Impact Strength (Charpy V‑notch, Room Temp) | ~100 – 150 J | ~40 – 80 J |
High-Temperature Mechanical Properties of Nimonic 75 and Nimonic 80A Alloys
| Temperature | Property | Nimonic 75 | Nimonic 80A |
|---|---|---|---|
| 500°C | Tensile Strength (Ultimate) | ~600 MPa | ~1050 MPa |
| Yield Strength (0.2%) | ~280 MPa | ~750 MPa | |
| 600°C | Tensile Strength (Ultimate) | ~550 MPa | ~950 MPa |
| Yield Strength (0.2%) | ~260 MPa | ~700 MPa | |
| 700°C | Tensile Strength (Ultimate) | ~450 MPa | ~800 MPa |
| Yield Strength (0.2%) | ~240 MPa | ~650 MPa | |
| 750°C | Tensile Strength (Ultimate) | ~380 MPa | ~700 MPa |
| Yield Strength (0.2%) | ~220 MPa | ~600 MPa | |
| 800°C | Tensile Strength (Ultimate) | ~300 MPa | ~550 MPa |
| Yield Strength (0.2%) | ~180 MPa | ~450 MPa |
Creep and stress fracture properties of Nimonic 75 and Nimonic 80A alloys
| Property | Nimonic 75 | Nimonic 80A |
|---|---|---|
| Creep Strength (1000 hours to 0.1% creep) | ||
| – at 600°C | ~100 MPa | ~250 MPa |
| – at 700°C | ~50 MPa | ~150 MPa |
| – at 750°C | ~30 MPa | ~100 MPa |
| Stress Rupture (1000 hours) | ||
| – at 700°C | ~80 MPa | ~200 MPa |
| – at 750°C | ~50 MPa | ~140 MPa |
| – at 800°C | ~30 MPa | ~90 MPa |
Contact our professionals to recommend alloys suitable for your project
3. Hot Working and Forging of Nimonic 75 (UNS NO6075)
Nimonic 75 has relatively good ductility and is easier to form than 80A. It is commonly used to manufacture combustion chambers, flame tubes, and plate components.
Forging temperature range: 982-1204°C (1800-2200°F).
Hot working temperature range: 950-1220°C (1740-2230°F).
Process flow:
o Heating should be rapid to the required temperature and held for a sufficient time.
o This alloy has good ductility and can withstand large deformations without fracture.
o Because it does not age harden, it has a lower risk of temperature-sensitive cracking during cooling compared to 80A.
Post-forging heat treatment: Annealing at 1050-1051°C (1925°F), followed by air cooling to optimize the microstructure. AZoM+2
Nimonic 75 VS Nimonic 80A
4. Hot Working and Forging of Nimonic 80A (UNS NO7080)
Nimonic 80A is designed for high-stress applications (e.g., turbine blades, exhaust valves) and requires careful handling during forging due to its precipitation hardening properties.
Forging Temperature Range: 1050-1200°C (1920-2190°F).
Optimal Forging Temperature: 950-1150°C is generally considered the practical range; temperatures above 1150°C may cause initial melting, especially at high strain rates.
Process Flow:
o Preheating/Holding: Typically preheated in a rotary kiln for 1 hour, or for large billets, held at 1080°C for 8 hours.
o Deformation: Due to the narrow forging range and relatively poor forging properties of this alloy, high-speed forging (e.g., screw press) is recommended. Cooling Method: Air cooling.
Defect control: Surface cracks may occur when the forging temperature is below 950°C.
Post-forging heat treatment: Solution treatment at 1080°C for 8 hours, air cooling, followed by aging treatment at 700°C for 16 hours to achieve the final mechanical properties.
Click to learn about the manufacturing process of Gnee Steel GH3030 alloy
5. Comparison of characteristics between Nimonic 75 and Nimonic 80A
| Feature | Nimonic 75 | Nimonic 80A |
|---|---|---|
| Strengthening | Solid Solution | Precipitation (Al + Ti) |
| Forging Temp | 982 - 1204°C | 1050 - 1200°C |
| Hot Workability | Excellent | Moderate to Poor |
| Forgeability | High | Low (higher load required) |
| Key Risk | Moderate to Low | Surface cracks / Incipient melting |
Contact us now to get the latest export price for GH3030 in 2026
FAQ
Q1: Why is the finish-forging temperature for Nimonic 80A so much higher than 75?
A: Nimonic 80A contains Aluminum (Al), which forms the γ′ phase. If you forge too cold, this phase begins to precipitate, making the material extremely hard and prone to "stress-induced cracking." Maintaining a high temperature (above 1050°C) keeps these elements in solution.
Q2: Can I air-cool Nimonic 75 after hot forging?
A: Yes, Nimonic 75 is a solid-solution alloy and is relatively stable. However, for Nimonic 80A, controlled cooling or rapid water quenching may be required depending on the cross-section to optimize the grain structure for subsequent aging.
Q3: What is the typical lead time for large diameter Nimonic billets?
A: We maintain a large inventory in stock for billets up to Φ150mm for immediate global shipping. For custom forging runs up to Φ350mm, our typical lead time is 4-6 weeks.