High temperature alloys
Nimonic 90

Equivalent alloy:

GH90(China), UNS No7090 (US), Nimonic90 (English),

Chemical composition:

Alloy

%

NI

CR

FE

MO

NB

CO

C

MO

SI

S

CU

A1

TI

Nimonic 90

The minimum

Margin

18.0

15.0

1.0

2.0

The maxmum

21.0

1.5

21.0

0.13

0.4

0.8

0.015

0.2

2.0

3.0

 

Physical properties:

The density
g/cm3

Melting point

Thermal conductivity
λ/(W/m•
)

Specific heat capacity
J/kg•

Modulus of elasticity 
GPa

Shear modulus
GPa

Linear expansion coefficient of
a/10-6-1

8.2

1400

21.76(100)

225

12.71(20~100)

 

Minimum mechanical properties at room temperature:

Heat treatment

Tensile strengthσb/MPa

The yield strengthσp0.2/MPa

elongationσ5 /%

hardness

Solution treatment

820

590

8

 

Metallographic microstructure structure: 
This alloy is mainly strengtheningPHase is gamma '- Ni3 (Ti, Al), in the intracrystalline with square makings shut precipitation of different size, on the grain boundary can also see the shape of the gamma'PHase and carbide precipitation on the grain boundary is discontinuous chains.

The main characteristics: 
Limitation of the alloy is improved high temperature deformation of nickel and cobalt base alloy, contains a high amount of cobalt and a variety of reinforcement element, the alloy in 815 ~815has higher tensile strength and creep resistance, good resistance to oxidation and corrosion resistance ability, in cold and hot again and again under the action of alternating have high fatigue strength and good formability and weldability. Lower than1040has good oxidation resistance and corrosion resistance ability, at above1040are prone to intergranular oxidation.

Process performance and requirements: 
1
Alloy during forging are prone to crack, to allow heavy hammer blow. Ingot furnace temperature is not higher than700, low temperature area to preheat the first 20-30 minutes, finally the heating temperature of1150to1180, open forging temperature is not lower than1050, the final forging temperature is not lower than950.
2
The size of the average grain size of the alloy and the forging deformation degree, finish forging temperature are closely related.Alloy in the solid solution state can be inert gas tungsten arc welding and flash butt welding.
3
furnace charging preheating 20-30 minutes after low temperature area, 1150-1180heat into the high temperature area.

 

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