Nimonic 80A: High-Temperature Strength & Turbine Blade Alloy

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Overview

Nimonic 80A (UNS N07080 / W.Nr. 2.4952) is a wrought, age-hardenable nickel-chromium alloy strengthened by additions of titanium and aluminum, which form a fine dispersion of gamma-prime (γ') precipitates (Ni3(Ti,Al)) during heat treatment. Developed in the 1940s by the Mond Nickel Company (later part of Special Metals), Nimonic 80A was the first of the Nimonic series of alloys specifically designed for high-temperature service, and it remains one of the most widely used superalloys for applications requiring high creep-rupture strength and oxidation resistance up to 815°C (1500°F).

The alloy derives its strength from a carefully balanced precipitation-hardening mechanism: titanium (1.8–2.7%) and aluminum (0.5–1.8%) combine with nickel to form coherent gamma-prime precipitates that impede dislocation movement at elevated temperatures. The chromium content (18–21%) provides excellent oxidation and hot corrosion resistance, while the controlled carbon content permits grain boundary carbide formation for enhanced creep resistance.

Nimonic 80A is extensively used for gas turbine blades, discs, rings, and casings in both aerospace and industrial gas turbines. It is also the standard material for high-performance internal combustion engine exhaust valves, where it withstands the combined effects of high temperature, thermal cycling, and corrosive combustion gases. Additional applications include high-temperature bolts, springs, and nuclear steam generator tubing where its stress relaxation resistance is critical.

Chemical Composition (AMS 5828 / BS HR1)

The chemical composition of Nimonic 80A is precisely controlled to achieve the optimal balance of gamma-prime precipitation strengthening, oxidation resistance, and fabricability. The titanium and aluminum levels are critical for controlling the volume fraction of gamma-prime phase (approximately 15–20 vol%) and the resulting mechanical properties after heat treatment.

Element	Min %	Max %
Nickel (Ni)	Balance	Balance
Chromium (Cr)	18.0	21.0
Titanium (Ti)	1.80	2.70
Aluminum (Al)	0.50	1.80
Iron (Fe)	—	3.0
Cobalt (Co)	—	1.0
Carbon (C)	—	0.10
Silicon (Si)	—	1.0
Manganese (Mn)	—	1.0
Copper (Cu)	—	0.20
Boron (B)	—	0.008
Phosphorus (P)	—	0.020
Sulfur (S)	—	0.015

Physical Properties

Nimonic 80A has an austenitic face-centered cubic (FCC) matrix with a dispersion of ordered gamma-prime (Ni3(Ti,Al)) precipitates. The physical properties are typical of nickel-based superalloys, with relatively low thermal conductivity and moderate thermal expansion that must be accounted for in design.

Property	Value	Unit
Density	8.19	g/cm3
Melting Range	1320–1365	°C
Specific Heat (20°C)	460	J/kg·K
Thermal Conductivity (20°C)	12.1	W/m·K
Electrical Resistivity (20°C)	1.23	μΩ·m
Modulus of Elasticity (20°C)	221	GPa
Mean Coefficient of Thermal Expansion (20–100°C)	11.8	μm/m·°C
Curie Temperature	< -100	°C

Heat Treatment

The mechanical properties of Nimonic 80A are developed through a two-stage precipitation-hardening heat treatment that controls the size, distribution, and volume fraction of gamma-prime precipitates. The standard heat treatment consists of:

• Solution Treatment: 1080°C (1975°F) for 8 hours, followed by air cooling. This dissolves all gamma-prime and carbide phases into solid solution.
• Precipitation Hardening: 700°C (1290°F) for 16 hours, followed by air cooling. This precipitates a fine, uniform dispersion of gamma-prime particles that provide the strengthening effect.

Alternative heat treatment schedules may be used for specific applications: a lower solution temperature (1038°C) followed by the standard aging treatment can produce higher tensile strength at the expense of some ductility. For creep-limited applications, a slightly higher aging temperature (750°C) is sometimes specified to improve long-term microstructural stability.

Mechanical Properties at Room Temperature

The following mechanical properties are typical for Nimonic 80A bar in the fully heat-treated condition (solution annealed + precipitation hardened) per AMS 5828. The alloy achieves its high strength through precipitation of gamma-prime phase during the aging treatment.

Property	Value
Tensile Strength (Rm)	1000 MPa (145 ksi)
Yield Strength, 0.2% offset (Rp0.2)	620 MPa (90 ksi)
Elongation in 4D	20%
Reduction of Area	25%
Hardness (Brinell)	270–340 HB
Modulus of Elasticity	221 GPa (32.1 × 106 psi)
Shear Modulus	84 GPa
Poisson's Ratio	0.30

High-Temperature Mechanical Properties

Nimonic 80A maintains significant strength at elevated temperatures due to the thermal stability of its gamma-prime precipitates. The alloy's strength retention at temperature is superior to solid-solution-strengthened nickel alloys, making it the preferred choice for rotating components in gas turbines and high-temperature fasteners.

Temperature (°C)	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation (%)
20 (Room)	1000	620	20
200	950	590	18
400	900	555	16
600	800	520	14
700	650	480	12
750	500	420	10
815	350	300	15

Creep-Rupture Properties

One of Nimonic 80A's most important characteristics is its outstanding creep-rupture resistance. The table below shows typical stress values required to produce rupture in 100, 1,000, and 10,000 hours at various temperatures.

Temperature (°C)	100-hr Rupture (MPa)	1,000-hr Rupture (MPa)	10,000-hr Rupture (MPa)
600	580	480	380
650	450	350	260
700	330	240	160
750	230	150	90
815	140	80	45

Corrosion and Oxidation Resistance

Nimonic 80A exhibits good oxidation resistance up to its maximum service temperature of 815°C through the formation of a protective chromium oxide (Cr2O3) scale. The alloy is not designed for wet corrosion service — its primary environmental resistance is to hot combustion gases and high-temperature oxidation.

Resistance Characteristics:

• High-Temperature Oxidation: The 18–21% chromium content provides good oxidation resistance in air and combustion gases up to 815°C. Scale formation is adherent and protective under thermal cycling conditions typical of gas turbine operation.
• Sulfidation Resistance: Moderate resistance to sulfidation attack from sulfur-containing fuels. The chromium content provides a degree of protection, but for severely sulfidizing environments, higher-chromium alloys or coatings may be required.
• Hot Corrosion (Type I & II): Adequate resistance to Type I hot corrosion (850–950°C) but limited resistance to Type II hot corrosion (650–750°C) caused by low-melting-point alkali metal sulfates. Protective coatings are recommended for long-term service in marine or industrial gas turbine environments.
• Aqueous Corrosion: The alloy offers moderate resistance to neutral and alkaline aqueous environments but is not designed for acid service. For aqueous corrosion applications, Ni-Cr-Mo alloys such as Alloy C-276 or Alloy 59 should be considered.

Applications

Nimonic 80A's unique combination of high-temperature strength, creep resistance, and oxidation resistance makes it essential for critical high-temperature components in multiple industries:

• Gas Turbine Components: Turbine blades, discs, rings, casings, and combustion chamber components in both aerospace (jet engine) and industrial (power generation) gas turbines. The alloy's creep-rupture strength at temperatures up to 815°C enables higher turbine inlet temperatures and improved thermal efficiency.
• Internal Combustion Engine Valves: Exhaust valves for high-performance diesel and gasoline engines. Nimonic 80A is the standard material for exhaust valves in heavy-duty truck, marine, and locomotive engines where exhaust gas temperatures can exceed 750°C. The alloy resists valve seat recession, burning, and corrosion from leaded and unleaded fuels.
• High-Temperature Fasteners: Bolts, studs, and nuts for flanged joints in steam turbines, gas turbines, and high-temperature process equipment. The alloy's high stress relaxation resistance maintains bolt preload at service temperature, preventing leaks in critical flanged connections.
• Nuclear Applications: Steam generator tubing support plates and other structural components in advanced gas-cooled reactors (AGR). The alloy's combination of high-temperature strength, oxidation resistance, and neutron irradiation tolerance is valued in nuclear designs.
• Hot Work Tooling: Hot forming dies, extrusion tooling, and piercing mandrels for processing of copper alloys and steels. The alloy maintains hardness and wear resistance at the elevated temperatures encountered during hot working operations.
• Springs: High-temperature springs for valve mechanisms, pressure relief devices, and furnace equipment where relaxation resistance at 500–700°C is critical.

Available Product Forms

Hangbo Alloy Group manufactures and supplies Nimonic 80A in the following product forms, conforming to AMS and BS specifications:

• Round Bars: AMS 5828, BS HR1, diameters from 6 mm to 300 mm, hot-finished or cold-drawn, solution treated and precipitation hardened.
• Forgings: Custom turbine blades, discs, rings, and shaped forgings per customer drawing. Hot forged from billet with controlled grain flow for optimum mechanical properties.
• Plates & Sheets: AMS 5871, thicknesses from 1.0 mm to 25 mm, hot-rolled or cold-rolled, heat treated.
• Seamless Tubes: BS HR401, sizes per customer specification, suitable for nuclear steam generator and heat exchanger applications.
• Fasteners: Custom bolts, studs, and nuts manufactured to customer specifications with full traceability and mechanical testing certification.

Related Standards

Standard	Description
AMS 5828	Bars and Forgings, Precipitation Hardenable
AMS 5871	Sheet and Strip, Precipitation Hardenable
BS HR1	Nickel-Chromium-Titanium-Aluminum Alloy Billets, Bars, Forgings, and Parts (Solution Treated + Precipitation Treated)
BS HR201	Nickel-Chromium-Titanium-Aluminum Alloy Sheet and Strip (Solution Treated)
BS HR401	Nickel-Chromium-Titanium-Aluminum Alloy Cold-Worked and Solution Treated Seamless Tubes
BS HR601	Nickel-Chromium-Titanium-Aluminum Alloy Rod and Sections for Machining (Solution Treated + Precipitation Treated)
DIN 17742	Wrought Nickel Alloys with Chromium — Chemical Composition
DIN 17752	Bars of Wrought Nickel and Nickel Alloys — Properties
ISO 9723	Nickel Alloy Bars

Contact Us for Nimonic 80A

Hangbo Alloy Group maintains inventory of Nimonic 80A bar, plate, and forging stock in standard sizes. We can provide mill test certificates per EN 10204 3.1, full chemical analysis, room and elevated temperature tensile testing, and stress-rupture testing to verify compliance with AMS and BS specifications.

For quotations, material certifications, or technical consultation on Nimonic 80A for your gas turbine, engine valve, or high-temperature fastener application, contact our technical sales team or call +86-136-1165-6360. We typically respond within 10 minutes during business hours.