What Is the Difference Between NIMONIC 75 Bar and NIMONIC 80 Bar?

In the world of high-temperature alloys, NIMONIC 75 and NIMONIC 80 are two well-known grades that have earned their place in demanding applications such as gas turbines, aerospace components, and heat treatment equipment. Both alloys belong to the NIMONIC family, a group of nickel-chromium-based superalloys known for their strength, corrosion resistance, and excellent thermal stability.

Although they share a similar base composition and are often used in high-temperature environments, NIMONIC 75 and NIMONIC 80 bars differ significantly in their alloying elements, mechanical properties, and performance characteristics. In this article, we’ll explore the key differences between NIMONIC 75 and NIMONIC 80 bars, and help you choose the right one for your specific application.

1. Overview of the NIMONIC Alloy Family

NIMONIC alloys were originally developed by the Wiggin Company (now part of Special Metals Corporation) to provide superior oxidation resistance and high-temperature performance. These alloys are primarily nickel-based with varying amounts of chromium, titanium, aluminum, and carbon, tailored to meet different performance needs.

NIMONIC bars are typically used in:

  • Jet engine components

  • Gas turbines

  • Fasteners and springs

  • Furnace parts

  • Heat exchanger tubes

Both NIMONIC 75 and 80 bars are widely available through trusted suppliers like sasaalloy, offered in various diameters, lengths, and surface finishes.

2. Chemical Composition Comparison

The most fundamental difference between NIMONIC 75 and NIMONIC 80 lies in their chemical makeup.

NIMONIC 75 Composition (%):

  • Nickel (Ni): ≥ 78.0

  • Chromium (Cr): 18.0 – 21.0

  • Iron (Fe): ≤ 5.0

  • Titanium (Ti): ≤ 0.35

  • Carbon (C): 0.08 – 0.15

  • Manganese (Mn): ≤ 1.0

  • Silicon (Si): ≤ 1.0

NIMONIC 80A Composition (%):

  • Nickel (Ni): ≥ 69.0

  • Chromium (Cr): 18.0 – 21.0

  • Iron (Fe): ≤ 3.0

  • Titanium (Ti): 1.8 – 2.7

  • Aluminum (Al): 1.0 – 1.8

  • Carbon (C): 0.06 max

  • Manganese (Mn): ≤ 1.0

  • Silicon (Si): ≤ 1.0

Key takeaway:
NIMONIC 80 contains significantly more titanium and aluminum, which are used for precipitation hardening, giving it higher strength and thermal fatigue resistance.

3. Mechanical Properties

Property NIMONIC 75 NIMONIC 80A
Tensile Strength (MPa) ~750 900 – 1000
Yield Strength (MPa) ~350 550 – 650
Elongation (%) ~40 ~20 – 25
Hardness (Rockwell B) ~85 ~95
Service Temperature (max) Up to 1000°C Up to 815°C (long term), higher for short periods

Conclusion:
NIMONIC 80A bars are stronger and harder than NIMONIC 75 bars, but NIMONIC 75 offers better formability and ductility.

4. Heat Treatment and Hardening

NIMONIC 75:

  • Supplied in annealed condition

  • Does not undergo precipitation hardening

  • Good formability and weldability

  • Ideal for formed components and mild thermal stress applications

NIMONIC 80A:

  • Strengthened by precipitation hardening (age hardening)

  • Requires solution treatment and aging for optimal performance

  • Higher strength at elevated temperatures

  • Suitable for load-bearing high-heat applications

5. Corrosion and Oxidation Resistance

Both NIMONIC 75 and 80 bars offer excellent oxidation and corrosion resistance, but:

  • NIMONIC 75 has better resistance in oxidizing environments such as furnace atmospheres, making it ideal for oxidation-prone applications.

  • NIMONIC 80A maintains good resistance but is engineered for strength rather than maximum corrosion resistance.

For example, NIMONIC 75 bars are often used in combustion chambers and heat shields, while NIMONIC 80A bars are common in rotating parts like turbine blades and fasteners.

6. Fabrication and Machinability

  • NIMONIC 75 is easier to machine, weld, and form due to its lower hardness and simple alloy structure.

  • NIMONIC 80A, while still machinable, is more difficult to form and machine due to its precipitation-hardened microstructure.

If your application involves extensive fabrication or cold working, NIMONIC 75 bar is the better option.

7. Typical Applications

NIMONIC 75 Applications:

  • Sheet metal components in aircraft engines

  • Gas turbine combustion chambers

  • Furnace parts and heat shields

  • Heat treatment equipment

  • Nuclear components

NIMONIC 80A Applications:

  • Turbine blades and discs

  • High-strength fasteners

  • Exhaust valves in internal combustion engines

  • Jet engine components

  • Springs for high-temperature use

sasaalloy supplies both NIMONIC 75 and NIMONIC 80A bars in full compliance with international standards such as ASTM B637 and AMS 5708.

8. Standards and Certifications

NIMONIC 75 Standards:

  • ASTM B637

  • AMS 5599 (sheet/strip)

  • BS HR5

NIMONIC 80A Standards:

  • ASTM B637

  • AMS 5829

  • BS HR1

All sasaalloy NIMONIC bars come with mill test certificates (MTCs) and can be supplied with third-party inspection reports if required.

9. Price and Availability

  • NIMONIC 75 is generally less expensive than NIMONIC 80A due to its simpler composition and lack of heat treatment.

  • NIMONIC 80A is more costly, but offers superior mechanical performance.

sasaalloy offers competitive pricing and fast lead times for both grades, ensuring project deadlines are met without compromising quality.

10. Summary Table

Feature NIMONIC 75 NIMONIC 80A
Base Composition Ni-Cr Ni-Cr-Ti-Al
Strength Moderate High
Ductility High Moderate
Heat Treatment Annealed only Precipitation hardened
Max Service Temperature ~1000°C ~815°C
Weldability Excellent Good
Applications Combustion, heat shields Turbine blades, fasteners
Cost Lower Higher

Conclusion

Both NIMONIC 75 and NIMONIC 80A bars are exceptional materials tailored for high-temperature applications. The choice between them depends largely on the mechanical demands, fabrication needs, and environmental conditions of your specific use case.

  • Choose NIMONIC 75 for easier fabrication, oxidation resistance, and cost-effective solutions in less mechanically demanding environments.

  • Choose NIMONIC 80A when higher strength and creep resistance are required under thermal stress and load-bearing conditions.

At sasaalloy, we offer high-quality NIMONIC 75 and NIMONIC 80A bars in custom sizes, heat treatments, and certifications tailored to your project needs. With decades of experience supplying specialty alloys to global industries, sasaalloy is your trusted partner in performance materials.

Post time: Jul-30-2025