Super alloys or high performance alloys have an ability to function at temperatures above 540ºC (1000ºF) with deformation resistance and high surface stability. As they have good oxidation and creep resistance, super alloys can be commonly forged, rolled to sheet or produced in various shapes. Iron-base, nickel-base and cobalt-base alloys are the major types of super alloys. Nickel-base and cobalt-base super alloys may be cast or wrought based on its composition or application. The iron-base super alloys are generally wrought alloys with stainless steel technology. These alloys can be strengthened by precipitation hardening, work hardening and solid-solution hardening.
The following section will provide details about Inconel 718 (UNS NO7718), which has superelastic formability, excellent corrosion resistance and high strength.
Chemical Composition
The following table shows the chemical composition of Super Alloy Inconel 718 (UNS NO7718) Seamless pipe.
| Elements | Content (%) |
|---|---|
| Nickel, Ni | 50-55 |
| Chromium, Cr | 17 - 21 |
| Iron, Fe | 19 |
| Niobium, Nb (Columbium, Cb) | 4.75-5.25 |
| Molybdenum, Mo | 2.80-3.30 |
| Cobalt, Co | ≤ 1 |
| Titanium, Ti | 0.65-1.15 |
| Silicon, Si | ≤ 0.35 |
| Manganese, Mn | ≤ 0.35 |
| Copper, Cu | ≤ 0.30 |
| Aluminum, Al | 0.20-0.80 |
| Carbon, C | ≤ 0.050 |
| Sulfur, S | ≤ 0.0020 |
| Phosphorous, P | ≤ 0.015 |
| Nitrogen, N | ≤ 0.010 |
| Boron, B | ≤ 0.0060 |
Physical Properties
The physical properties of Super Alloy Inconel 718 (UNS NO7718) Seamless pipe are given in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Density | 8.19 g/cm³ | 0.296 lb/in³ |
Mechanical Properties
The mechanical properties of Super Alloy Inconel 718 (UNS NO7718) Seamless pipe are displayed in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Tensile strength | 1120 MPa | 162000 psi |
| Yield strength (at 0.2%) | 827 MPa | 120000 psi |
| Modulus of elasticity | 205 GPa | 29700 ksi |
| Poissons ratio | 0.284 | 0.284 |
| Elongation at break | 31% | 31% |
| Hardness, Rockwell C | 24 | 24 |
Thermal Properties
The thermal properties of Super Alloy Inconel 718 (UNS NO7718) Seamless pipe are displayed in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Thermal expansion co-efficient (at 21-93ºC/69.8-199ºF, mean; annealed and aged) | 12.5 µm/m°C | 6.750 µin/in°F |
| Thermal conductivity | 11.1 W/mK | 77 BTU in/hr.ft².°F |
