Alloy 718
2.4668 – N07718
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Material description
The material 2.4668 is a precipitation-hardenable nickel-chromium alloy. In addition to iron, niobium and molybdenum, the material also contains small amounts of aluminium and titanium.
The alloy 2.4668 (Alloy 718) has good corrosion resistance and high strength. The material is also resistant to the formation of welding cracks. 2.4668 has very good creep rupture strength at temperatures of up to approx. 750 °C and high fatigue strength in the temperature range between -250 °C and 700 °C. The alloy is also oxidation-resistant up to approx. 980 °C.
AN OVERVIEW OF THE PROPERTIES OF 2.4668:
- Good corrosion resistance
- High strength
- Resistant to the formation of welding cracks
- High creep and fatigue strength
- Good oxidation resistance
Applications
- Gas turbines
- Nuclear technology
- Space travel
- Rocket engines
Chemical composition in %
| ASTM B637 | DIN EN 10302 | API 6A718 | |
|---|---|---|---|
| C | max. 0,08 | 0,020 – 0,08 | max. 0,045 |
| Mn, max. | 0,35 | 0,35 | 0,35 |
| Si, max. | 0,35 | 0,35 | 0,35 |
| P, max. | 0,015 | 0,015 | 0,010 |
| S, max. | 0,015 | 0,015 | 0,010 |
| Cr | 17,0 – 21,0 | 17,0 – 21,0 | 17,0 – 21,0 |
| Co, max. | 1,0 | 1,00 | 1,00 |
| Mo | 2,80 – 3,30 | 2,80 – 3,3 | 2,80 – 3,30 |
| Nb + Ta | 4,75 – 5,50 | 4,7 – 5,5 | 4,87 – 5,20 |
| Ti | 0,65 – 1,15 | 0,60 – 1,20 | 0,80 – 1,15 |
| Al | 0,20 – 0,80 | 0,30 – 0,70 | 0,40 – 0,60 |
| B | max. 0,006 | 0,002 – 0,006 | max. 0,0060 |
| Fe | Rest | Rest | Rest |
| Cu, max. | 0,30 | 0,30 | 0,23 |
| Ni | 50,0 – 55,0 | 50,0 – 55,0 | 50,0 – 55,0 |
| Pb, max. | 0,0010 | ||
| Se, max. | 0,0005 | ||
| Bi, max. | 0,00005 | ||
| Ca, max. | *0,0030 | ||
| Mg, max. | *0,0060 |
Mechanical properties
| solution annealed + precipitation hardened | Bar | forging | Bar | forging D ≤ 160 mm | Bar | forging D < 76 mm / 76 mm ≤ D ≤ 254 mm / D > 254 mm |
|---|---|---|---|
| Rm (MPa) | ≥ 1275 | ≥ 1230 | ≥ 1034 |
| Rp 0,2 (MPa) | ≥ 1034 | ≥ 1030 | 827 – 1000 |
| A (%) | ≥ 12 | ≥ 12 | ≥ 20 |
| Z (%) | ≥ 15 | ≥ 35 / ≥ 35 / ≥ 25 | |
| Av (J) bei -60 °C | l ≥ 68 (61)* / q ≥ 47 (41)* / q ≥ 41 (37)* | ||
| lateral expansion (mm) | ≥ 0,38 | ||
| Hardness | ≥ 331 HB | 32 – 40 HRC |
The specified values are non-binding guide values.