Nimonic 80A is a nickel-chromium-cobalt alloy that offers high-temperature strength and corrosion resistance, making it useful in a variety of demanding applications. As a ‘superalloy’, nimonic 80A exhibits excellent mechanical properties and stability at temperatures up to 1000°C. Its unique properties stem from its complex metallurgy consisting of multiple alloying elements that provide solid solution, precipitation and oxide dispersion strengthening.

Composition and Microstructure

Nimonic 80A has a nominal composition of nickel, 19-21% chromium, 8-10% cobalt, up to 3% molybdenum, 1.3-1.7% titanium, 0.8-1.2% aluminium and trace elements like zirconium and boron. The microstructure consists of an austenitic face-centred cubic matrix with coherent precipitates of Ni3(Ti,Al) called gamma prime. Additional strengthening comes from carbides, nitrides and oxides present in the alloy.

Manufacturing Process

Nimonic 80A is usually produced by vacuum induction melting followed by vacuum arc remelting to achieve homogeneity. The ingots are then hot worked through cogging and forging operations to break down segregation patterns and develop a fine, uniform grain size suited for further working. Additional heat treatments serve to solution anneal the alloy and allow precipitation of the strengthening phases.

Properties and Performance

The combination of solid solution, precipitation and dispersion strengthening gives Nimonic 80A an excellent balance of high strength and good ductility across a wide temperature range up to around 800°C. It has relatively good oxidation resistance up to 950°C. Other notable properties include:

– Tensile strength: 850-1030 MPa

– 0.2% Yield strength: ≥760 MPa 

– Elongation: 35%

– Melting point: 1315-1390°C

The alloy retains appreciable strength and resisting deformation at high operating stresses and temperatures. It is readily fabricated and welded using conventional techniques. These well-rounded properties enable the use of Nimonic 80A in critical high-temperature environments.

Applications

Nimonic 80A finds use in components and assemblies meant for long-term service under extreme heat and/or corrosive conditions:

– Gas turbine hot section parts – blades, discs, combustors

– Turbocharger and exhaust valves in internal combustion engines 

– Heat exchangers and recuperators

– Furnace muffle materials

– Nuclear fuel element cladding

– Flight data recorders and engine fire detectors

Its capability to withstand high temperatures and oxidation over thousands of hours makes Nimonic 80A invaluable for such challenging applications in aerospace, power generation, chemical processing and automotive sectors.

With its excellent elevated temperature strength, corrosion resistance and fabricability, Nimonic 80A is a versatile nickel superalloy suitable for manufactured components and structures meant to perform reliably in the harshest environments. Its carefully tailored composition and microstructure provide an exceptional combination of properties unmatched by common alloy systems. Nimonic 80A continues to play a critical role in pushing the boundaries of high-temperature materials technology.