Multimet (N155) Alloy

Chemical Analysis
C Carbon
0.08 – 0.16
Mn Manganese
1.00 – 2.00 max
Si Silicon
1.00 max
S Sulfur
0.03 max
P Phosphorus
0.04 max
Cr Chromium
20.00 – 22.5
Ni Nickel
19.00 – 21.00
Co Cobalt
18.5 – 21.00
Mo Molybdenum
2.5 – 3.5
W Tungsten
2.0 – 3.0
Cb + Ta Niobium + Tantalum
0.75 – 1.25
N Nitrogen
0.1 – 0.2

General characteristics of Multimet (N155) Alloy

Multimet alloy is a nickel-chromium-cobalt alloy with molybdenum, tungsten and columbium additions. As such it has good high-temperature properties and may be used to 1500ºF (815ºC) where high stresses are involved and up to 2000ºF where stresses are moderate. The alloy has good ductility, excellent oxidation resistance, and may be readily fabricated and machined.


N155 alloy is used in numerous aircraft applications, including tail cones and tail pipes, exhaust manifolds, combustion chambers, afterburners, turbine blades and buckets, and bolts.


Forging of ingots should be carried out at 2200ºF (1205ºC) following thorough soaking. Forging of semi-finished products may be started at 2150ºF (1175ºC) and may be carried on down to around 1900ºF (1040ºC) prior to the necessity for reheating.

Heat treatment

Solution treatment may be carried out at 2100/2280ºF (1150/1250ºC) for one hour followed by rapid cooling, with the higher temperature giving the highest rupture strength and the lower temperature giving the best ductility.

Aging may be carried out at 1400/1500ºF (760/815ºC) for 16 hours followed by air cooling.


Low speeds and positive feeds together with a rigid set up are the order of the day for machining this alloy. Machinability will be better in the fully heat-treated condition.


N155 may be welded by metallic-arc, inert-gas-shielded arc and solid-phase pressure welding methods.


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