Inconel® 718 tubing was
initially developed for the aerospace industry but its excellent strength and
corrosion resistance were recognised by the oil industry and it is now widely
used in this field as well.
Inconel® 718 tubing is a nickel-chromium alloy which can be heat-treated to
give high strength, good corrosion resistance, ease of formability and which
can be welded with good resistance to strain age cracking. The alloy can be
used at temperatures up to 700ºC.
For aerospace and power generation, Inconel® 718 tubing is heat treated such
that the hardness does not exceed 40HRC which is the maximum allowed by NACE
MR-01-75/ ISO 15156: 3 to prevent stress corrosion cracking. The major
applications in this field are Valves and precision tubing.
Alloy 718 for aerospace and power generation is heat treated to give maximum
strength and high creep resistance with typical hardness values exceeding
42HRC. The major applications are components for gas turbines, aircraft engines,
fasteners and other high strength applications.
Mechanical Properties
Temper |
Solution-treated |
|
Tensile Rm |
155 |
ksi (Max) |
Tensile Rm |
1069 |
MPa (Max) |
R.p. 0.2% Yield |
95 |
ksi (Max) |
R.p. 0.2% Yield |
655 |
MPa (Max) |
Elongation (2” or 4D gl) |
30 |
% (min) |
Physical Properties (Room Temperature)
Specific Heat (0-100°C) |
435 |
J.kg-1.°K-1 |
Thermal Conductivity |
11.4 |
W.m -1.°K-1 |
Thermal Expansion |
13 |
μm/μm/°C |
Modulus Elasticity |
200 |
GPa |
Electrical Resistivity |
1.32 |
Ohm-cm |
Density |
8.19 |
g/cm3 |
Chemical Composition (% by weight)
|
||
Element |
Min |
Max |
C |
- |
0.08 |
Si |
- |
0.35 |
Mn |
- |
0.35 |
P |
- |
0.015 |
Al |
0.2 |
0.8 |
B |
- |
0.6 |
Co |
- |
1 |
Cr |
17 |
21 |
Cu |
- |
0.3 |
Fe |
Balance |
|
Mo |
2.8 |
3.3 |
Nb |
4.75 |
5.5 |
Ni |
50 |
55 |
Ti |
0.65 |
1.15 |