Inconel 718 is a nickel-based super alloy that is well suited for applications requiring high strength in temperature ranges from cryogenic up to 1400°F. Inconel 718 also exhibits excellent tensile and impact strength.
Inconel 718 is a nickel-based super alloy that is well suited for applications requiring high strength in temperature ranges from cryogenic up to 1400°F. Inconel 718 also exhibits excellent tensile and impact strength.
| Zeon Grade | Alloy Name | UNS | EN / DIN / W Nr. | Trademarks |
|---|---|---|---|---|
| Zeon718 | Alloy 718 | UNS N07718 | 2.4668 | Inconel 718 |
| Elements | Percentage |
|---|---|
| Carbon | 0.08 max |
| Manganese | 0.35 max |
| Phosphorus | 0.015 max |
| Sulfur | 0.015 max |
| Silicon | 0.35 max |
| Chromium | 17-21 |
| Nickel | 50-55 |
| Molybdenum | 2.80-3.30 |
| Columbium | 4.75-5.50 |
| Titanium | 0.65-1.15 |
| Aluminum | 0.20-0.80 |
| Cobalt | 1.00 max |
| Boron | 0.006 max |
| Copper | 0.30 max |
| Tantalum | 0.05 max |
| Iron | Balance |
| Properties | Solution Treated | Solution Treated and Aged |
|---|---|---|
| Density | 0.296 lb/in3 (8.192 g/cm3) | 0.297 lb/in3 (8.22 g/cm3) |
| Specific Gravity | 8.19 | 8.22 |
| Melting point | 2500-2600°F | 1370-1430°C |
| Yield Strength Min (0.2% offset) | Ultimate Tensile Strength Min | Elongation (% in 2") |
|---|---|---|
| 150,000 (1,035 MPa) | 180,000 psi (1,240 MPa) | 12 (min) |
| Temperature Range | Co-Efficients | ||
|---|---|---|---|
| °C | °F | W/m.K | Btu.ft/ft2.hr.°F |
| 0-100 | 532-212 | 6.5 | 11.2 |
| Corrosion Resistance Properties of Alloy 718 |
|---|
| Based on the high chrome and molybdenum concentrations, UNS N07718 has a good resistance in many media against abrasive and local corrosion such as pitting. By virtue of its high nickel content, UNS N07718 also has good resistance against stress corrosion cracking. |
| Heat treatment | Workpieces must be clean and free of any contaminants before and during heat treatment. Sulfur, phosphor, lead and other low-melting-point metals can lead to damage when heat treating UNS N07718. Sources of such contaminants include marking and temperature-indicating paints and crayons, lubricating grease and fluids, and fuels. Heat treatments can be carried out in gas fired, oil fired or electric furnaces in air, under vacuum or inert gas atmosphere. Fuels should contain as little sulfur as possible. Natural gas should contain less than 0.1 wt.-% of sulfur. Heating oil with a sulfur content of maximum 0.5 wt.-% is also suitable with a slightly oxidizing atmosphere. The workpieces may not be contacted directly by flames. |
|---|---|
| Hot working | The hot working should generally be conducted after the homogenization with subsequent cooling in air. It should be done evenly in order to receive a homogeneous structure and to prevent the formation of a duplex grain structure. |
| Cold working | Cold working should take place in the solution-annealed condition. The material has a higher work hardening rate than austenitic stainless steels. This must be taken into account during design and selection of forming tools and equipment and during the planning of the forming processes. |
| Descaling and pickling | Oxides from UNS N07718 and discoloration adjacent to welds are more adherent than on stainless steels. Grinding with very fine abrasive belts or discs is recommended. Care should be taken to prevent tarnishing. Before pickling which may be performed in a nitric/hydrofluoric acid mixture with proper control of pickling time and temperature, the surface oxide layer must be broken up by abrasive blasting or by carefully performed grinding. |
| Machining | While UNS N07718 in the solution-annealed condition is easier to process and the strain on tools is less, better surface quality is achieved in the hardened condition. The best results in terms of the surface quality of the finished product are achieved by pre-treatment before hardening and by finishing in the hardened condition. |
| Welding | UNS N07718 can be welded in a number of different welding processes. Wherever the inert gas welding process is used, impulse technology is preferable. The material should be in the solution-annealed condition for welding, and should be free of scale, grease and markings. When welding the root, care should be taken to achieve best quality root backing (e.g. argon 4.6), so that the weld is free from oxides after welding the root. Any temper colors must be removed, preferably using a stainless steel brush, while the welding seam is still hot. |
| Applications | it has been used in jet engine and high-speed airframe parts, including wheels, fasteners, instrumentation parts, bolts, spacers and buckets. It is also used to engineer components for liquid-fuelled rockets, rings and casings, as well as various formed sheet metal parts for turbine engines, both aircraft and land-based. At the other end of the temperature scale, INCONEL alloy 718 is also used in cryogenic tankage. |