Nimonic 80A: An Age Hardenable Super Alloy with High Temperature Strength
Alloy Definition and Chemical Composition
Nimonic 80A consists essentially of the elements nickel (balance) and chromium (19–21%) and is an age hardenable super alloy developed for high temperature applications. Thanks to being able to preserve its mechanical strength for a long time in the 650–850 °C range, this alloy is preferred in the production of critical parts especially in gas turbines, exhaust systems and nuclear applications.
Age hardening is obtained with the γ′ (Ni₃(Al,Ti)) phase precipitates provided by the Ti and Al additions. This precipitate phase restricts dislocation movement within the matrix and thereby provides high resistance to the softening that increases with temperature.
Typical chemical composition (% by weight):
- Nickel (Ni): 76.0% (balance)
- Chromium (Cr): 19.0 – 21.0%
- Iron (Fe): ≤3.0%
- Titanium (Ti): 1.8 – 2.7%
- Aluminium (Al): 1.0 – 1.8%
- Carbon (C): ≤0.10%
- Manganese (Mn): ≤1.0%
- Silicon (Si): ≤1.0%
- Copper (Cu): ≤0.2%
- Sulphur (S): ≤0.015%
The combined Ti and Al content is generally kept between 3.5–4%; this constitutes the critical threshold for the formation of the γ′ phase.
Nimonic 80A Standards and Specifications
Nimonic 80A has been defined in the following international standards:
- BS HR1 / HR6018 – British Standard designations
- UNS N07080 – Unified Numbering System
- AMS 4378 – For bar, forged and formed products
- AMS 5829 – Wire products
- ISO 15156-3 / NACE MR0175 – Approval for use in H₂S environments
In addition, although it has no direct equivalent in ASTM, it is used together with general specifications for forged nickel alloys such as ASTM B637.
Nimonic 80A Trade Names and Equivalent Alloys
- Nimonic® 80A – Registered name of Special Metals Corporation (SMC)
- UNS N07080
- ATI 80A, VDM Alloy 80A, Haynes 80A – Different producer names
- Close equivalent: Inconel X-750 (for higher temperature strength)
Nimonic 80A Mechanical and Physical Properties
Nimonic 80A provides high strength and oxidation resistance after the solution annealing + aging operation.
Typical properties in the age hardened condition:
- Tensile strength (UTS): 1000–1200 MPa
- Yield strength (0.2%): 700–850 MPa
- Elongation (%): 15–20
- Hardness (Rockwell B): HRB 95 – HRC 30
- Temperature range: -200 °C to 850 °C
- Density: 8.19 g/cm³
- Melting range: 1320–1380 °C
Oxidation resistance is very high at service temperatures up to 900 °C. It therefore offers a long service life in environmentally aggressive conditions such as turbine blades and exhaust manifolds.
Application Areas
Nimonic 80A has a broad area of use in the production of parts exposed to high temperature:
1.Aerospace and Gas Turbine Systems
#Turbine blades, gaskets, brackets, fixing elements
2.Nuclear Energy
#In-reactor elements, bolts with high temperature strength
3.Automotive and Motorsport
#Turbocharger blades, exhaust systems
4.Chemical Process Industry
#Parts and fasteners resistant to corrosion and thermal stress
5.Petrochemicals
#Fittings in environments containing H₂S and high temperature
6.Power Plants
#Heat resistant welding filler metal, fixing elements
Advantages
- High Temperature Strength: It preserves its mechanical stability up to 850 °C.
- Precipitation Hardening (γ′): The stable age hardening structure prevents deformation in long-term service.
- High Oxidation Resistance: It is resistant to dry and wet oxidising environments.
- Thermal Fatigue Resistance: Its resistance to cracking and deformation against repeated thermal cycles is high.
- Weldability: It can be welded more easily than other nickel alloys; however, preheating and controlled cooling may be required.
Disadvantages
- Machining Difficulty: Because of its high hardness and ductile structure, special cutting tips and a low feed rate are required.
- Heat Treatment Sensitivity: If the appropriate solution treatment and ageing are not carried out, the expected mechanical properties cannot be reached.
- High Cost: It is more expensive than austenitic stainless steels.
- Ductile-Brittle transition: It may show a tendency to brittle fracture at low temperatures.
Conclusion and Engineering Evaluation
Nimonic 80A stands out with its balanced performance among the heat resistant, precipitation hardenable nickel-based alloys. Its high temperature strength, resistance to thermal fatigue and oxidation durability in particular make it an indispensable material in gas turbine components and aircraft engines.
For design engineers this alloy offers a reliable choice in applications requiring both structural strength and environmental resistance. Provided that the ageing process is controlled correctly, it stands out with the advantages of a long service life and dimensional stability.
#BSHR1
#HR6018
#UNSN07080
#AMS4378
#AMS5829
#ISO15156-3
#NACEMR0175
#Nimonic®80A
#UNSN07080
#ATI80A
#VDMAlloy80A
#Haynes80A
We supply this material
We supply Nimonic 80A — to AMS 5829, AMS 4378 standards, in the dimensions and forms required. Contact us for stock availability and pricing.
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