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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.
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Nickel
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50.0
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55.0
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Chromium
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17.00
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21.00
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Molybdenum
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2.80
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3.30
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Carbon
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-
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0.045
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Columbian + Tantalum
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4.87
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5.20
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Manganese
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-
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0.35
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Silicon
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-
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0.35
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Phosphorus
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-
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0.010
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Sulfur
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-
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0.010
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Copper
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-
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0.230
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Cobalt
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-
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1.00
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Lead
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-
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10 ppm
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Selenium
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-
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5 ppm
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Bismuth
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-
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30 ppm
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Magnesium
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-
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60 ppm
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Iron
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-
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remainder
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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
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Density:
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0.297 lb/inch3
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Melting Range:
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2160 - 2449°F
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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.
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70
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-
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6.4
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29.0
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200
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7.3
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7.2
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28.4
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400
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7.5
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8.2
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27.6
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600
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7.7
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9.3
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26.7
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1000
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8.1
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11.3
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24.8
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1200
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8.4
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12.3
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23.7
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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.
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Ultimate Tensile Strength
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150 ksi
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-
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0.2% Yield
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125 ksi
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145 ksi
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Elongation
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20%
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-
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Reduction of Area
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35%
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-
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Impact Strength*
Min Average/Min Single
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40/35 ft-lbs
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-
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Hardness
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32 RC
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40 RC
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* Charpy V notch impact test performed at -75 ˚F
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