Lower Coefficient of expansion of Ni-Fe alloy Ni-span C902

The coefficients of expansion of the soft Ni-Fe alloy Ni-span C902 at the different range of heat processing’s is shown in the following table:

Form Coefficient of Thermal Expansion, /in./°F x 10
-40 to 78°F 78 to 200°F 78 to 300°F 78 to 400°F
As hot rolled 4.5 4.5 4.6 6.0
1850°F/1 hr, WC 4.2 4.3 4.4 5.5
1850°F/1 hr, WC +

900°F/5 hrs, AC

4.3 4.2 4.3 5.6
1850°F/1 hr, WC +

1000°F/5 hrs, AC

4.4 4.2 4.4 5.9
1850°F/1 hr, WC +

1100°F/5 hrs, AC

3.9 4.2 4.6 6.0

It can be easily observed that the heat processing doesn’t have considerable effect on the coefficient of expansion. The other analysis performed describe that the cold processing of alloy before the heat processing has nominal effect on the coefficient of expansion. The stable lower rate of expansion is obtained by the significant working limit. The temperature level at which the expansion rate is obtained increases the rate quickly is called as the inflection point. It is calculated from the total expansion graph. This nature of Ni-span C902 alloy shows the lower expansion kind. The tensile modulus of elasticity is obtained between 24 – 29 x 10(3) depends on the treatment. The torsional modulus range is 9-10 x 10(3) ksi.

The physical properties of Ni-span C902 are described as following:

Density, lb/in3, g/cm3 0.291, 8.05
Melting Range, °F, °C 2650-2700, 1450-1480
Specific Heat, Btu/lb•°F, J/kg•°C 0.12,500
Curie Temperature, °F, oC 380, 190
Electrical Resistivity, ohm•cmil/ft, µΩ•m 611, 1.02

The thermal conductivity of age hardened Ni-span C902 at 1260oF for 6 hours is provided below:

Temperature, oF Thermal Conductivity BTU/sq. ft./hr/°F/in.
-238 52.7
-148 63.1
32 80.4
212 95.0
392 106.8
572 117.9
752 127.6
932 137.3
1004 141.4

The effect of cold processing and thermal processing on the room temperature tensile modulus is determined. The cold processing increases the tensile modulus. The increase in temperature of heat processing also increases the modulus. The effect of triple heat processing’s on the tensile modulus of cold treated strip at the various temperature ranges is observed. The quick alterations at temperature more than 250oF are caused by the quick alteration in the magnetic properties more than this temperature. The highest temperature is an approximate determinant of curie temperature of the alloy.

The room temperature tensile strength and toughness are described in the below table:

Form Tensile strength, ksi Yield strength, ksi Elongation  % Toughness, Rc
As rolled 131.0 126.0 6.5 26
500°F/5 hrs 139.0 136.0 7.0 29
900°F/5 hrs 140.5 135.0 11.0 30
1000°F/5 hrs 150.0 137.0 12.0 33
1100°F/5 hrs 178.5 165.0 9.5 37
1200°F/5 hrs 192.0 176.0 9.0 40
1300°F/5 hrs 193.0 173.0 8.5 40

From the above table it can easily understood that how heat processing is required at temperature of 1100 – 1300oF at any instant. The fatigue strength at the room temperature is shown in the underneath table:

Form and Condition Endurance Limit (10 – 8cycles), ksi
Bar, aged 50
Sheet, cold rolled & aged 50
Sheet, annealed & aged 40
Bar, aged – torsion 18

Isha Changotra has wide experience in metals industry and is working for a renowned super alloys manufacturer located in China and United States. With extensive insight in metals and high performance super alloys, she aims to provide most useful information for folks engaged under this niche.

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Posted in Ni-Fe alloy Ni-span C902 plate, Ni-span C902 plate

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