Alloy 718

Introduction:

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

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

Applications of Nickel Alloy 718

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

Chemical 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 of Alloy 718

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:-

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

Mechanical Properties of Nickel Alloy 718:-

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

 

Alloy 718 Avaliability

Alloy 718 Specifications

Alloy 718 Tensile Requirements