Nickel Alloy 718 – Properties, Composition, Heat Treatments and Specifications

Nickel Alloy 718 is a precipitation hardenable nickel-chromium alloy. It combines high strength in the aged condition with good corrosion resistance and weldability.

718 NACE indicates material stocked in the heat treated condition to have high strength and meet the maximum hardness (40 Rockwell C) requirements of the NACE MR0175, MR0103, ISO 15156-3 specifications for use in oil tools used for sour service.

Features of Nickel Alloy 718

The key features of Nickel Alloy 718 include:

  • Highly resistant to chloride and sulfide stress corrosion cracking
  • High strength in the aged condition
  • Good corrosion resistance

Performance Profile for Nickel Alloy 718

Nickel Alloy 718 is a precipitation hardenable nickel-chromium alloy. It combines high strength in the aged condition with good corrosion resistance and weldability.

718 NACE indicates material stocked in the heat treated condition to have high strength and meet the maximum hardness (40 Rockwell C) requirements of the NACE MR0175, MR0103, ISO 15156-3 specifications for use in oil tools used for sour service.

Applications of Nickel Alloy 718

Typical Applications for the Nickel Alloy 718 include:

  • Valves
  • Well head completion equipment
  • Fasteners
  • Blow out preventers (BOPs)
  • Tubing hangers
  • Mandrels

Composition of Nickel Alloy 718

The composition range for Nickel Alloy 718 is provided in table 1.

Table 1. Composition of nickel alloy 718.

Chemistry, %

AMS 4967

Min

Max

Nickel

50.0

55.0

Chromium

17.00

21.00

Molybdenum

2.80

3.30

Carbon

-

0.045

Columbian + Tantalum

4.87

5.20

Manganese

-

0.35

Silicon

-

0.35

Phosphorus

-

0.010

Sulfur

-

0.010

Copper

-

0.230

Cobalt

-

1.00

Lead

-

10 ppm

Selenium

-

5 ppm

Bismuth

-

30 ppm

Magnesium

-

60 ppm

Iron

-

remainder

Specifications

The various forms of nickel alloy 718 are covered by the following standards:

  • API 6A
  • API 6A718
  • NACE MR0175, MR0103
  • ISO 15156-3
  • ASTM B 637

Heat Treatments

718 NACE is annealed between 1875-1925°F and water quenched. Subsequently it is aged in the range of 1425°-1475°F for 6-8 hours and air cooled or faster to room temperature.

Physical Properties of Nickel Alloy 718

Density:

0.297 lb/inch3

Melting Range:

2160 - 2449°F

Thermal Properties of Nickel Alloy 718

The thermal properties of Nickel Alloy 718 are summarised in table 2.

Table 2. Thermal properties of Nickel Alloy 718.

Temp

Coefficient of Thermal Exp.

Thermal Conductivity

Modulus of Elasticity Dynamic

°F

in/in °F x 10-6

Btu. ft/ft2.hr°F

psi x 106

70

-

6.4

29.0

200

7.3

7.2

28.4

400

7.5

8.2

27.6

600

7.7

9.3

26.7

1000

8.1

11.3

24.8

1200

8.4

12.3

23.7

Typical Mechanical Properties of Nickel Alloy 718

The minimum mechanical properties of nickel alloy 718 are provided in table 3.

Table 3. Minimum specified properties of nickel alloy 718, solution annealed and aged condition.

Property

Minimum

Maximum

Ultimate Tensile Strength

150 ksi

-

0.2% Yield

125 ksi

145 ksi

Elongation

20%

-

Reduction of Area

35%

-

Impact Strength*
Min Average/Min Single

40/35 ft-lbs

-

Hardness

32 RC

40 RC

* Charpy V notch impact test performed at -75 ˚F

This information has been sourced, reviewed and adapted from materials provided by NeoNickel.

For more information on this source, please visit NeoNickel.

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Comments

  1. Loto Tolulope Loto Tolulope Nigeria says:

    What is the equivalent weight of nickel alloy 718

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