24 July 2021 Nimonic®
Nimonic 81 Nickel Based Superalloy
NIMONIC® alloy 81 is a wrought nickel alloy hardened by controlled additions of titanium and aluminum, and designed to provide enhanced resistance to high temperature corrosion coupled with good high temperature strength. It has excellent hot corrosion resistance due to its high chromium content.
Elevated temperature strength characteristics are similar to those of NIMONIC alloy 80A. Melting, hot-working, cold-working and machining practices are also broadly similar to those for NIMONIC alloy 80A. Applications include components for gas turbines, piston engine exhaust valves, and heat-exchange plant subject to attack by deposits resulting from the combustion of impure fuels, particularly by alkali metal sulfates and chlorides.
NIMONIC alloy 81 is normally used in the solution- and precipitation-treated condition. This heat treatment is generally carried out in air. Material is usually supplied in the solution-treated condition and is aged by the customer as part of the fabrication process. NIMONIC alloy 81 can, however, be supplied to any requested heat-treatment condition. Details of the recommended heat treatments for various forms are given below, where the stated times represent the times at temperature. In establishing furnacing time due allowance must, of course, be made for furnace characteristics and charge weight.
Mechanical Properties:
| Material | Ultimate Tensile Strength (MPA) | 0.2 % Yield Strength (MPA) | % Elongation |
|---|---|---|---|
Nimonic 81 | 874 | 565 | 14 |
Nimonic® 81 Chemical Composition:
| Element | Content (%) |
|---|---|
| Nickel, Ni | 63 |
| Chromium, Cr | ≤30 |
| Cobalt, Co | ≤2 |
| Titanium, Ti | 1.8 |
| Iron, Fe | ≤1.0 |
| Aluminum, Al | 0.9 |
| Others | Remainder |
Nimonic® 81 Physical Properties:
| Properties | Metric | Imperial |
|---|---|---|
| Density | 8.06 gm/cm3 | 0.291 lb/in3 |
Nimonic® 81 Heat Treatment:
Nimonic® 81 Hot working
NIMONIC alloy 81 can be hot worked at temperature ranges of 950-1160°C (1742-2120°F).
Nimonic® 81 Forging
NIMONIC alloy 81 can be hot forged at temperatures in the range of 1010-1176°C (1850-2150°F).
Nimonic® 81 Cold working
Cold working may be done on the alloy for hardening.
Nimonic® 81 Annealing
NIMONIC alloy 81 should be solution annealed at 1098°C (2010°F) for about 8 hours.
Nimonic® 81 Applications
Heat exchange plant.
Gas turbine engineering
Piston engine exhaust valves