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Grades and composition
Seven nickel grades, each bought for a different balance of strength, oxidation and weldability.
| Grade | UNS | Family | Service ceiling | Chosen when |
|---|---|---|---|---|
| Inconel 718 | UNS N07718 | NiCrFe + Nb, Mo | 700 °C | Age-hardenable; the volume grade for discs, shafts and valve bodies |
| Inconel X-750 | UNS N07750 | NiCr + Ti, Al | 815 °C | Age-hardenable, good relaxation resistance at temperature |
| Inconel 625 | UNS N06625 | NiCrMo + Nb | 980 °C | Corrosion plus strength; used where the service is chemical as well as hot |
| Inconel 600 | UNS N06600 | NiCr 76/15 | 1,100 °C | Oxidation resistance; furnace and heat-treat fixtures |
| Waspaloy | UNS N07001 | NiCrCoMo + Ti, Al | 870 °C | Higher temperature strength than 718; compressor and turbine hardware |
| Rene 41 | UNS N07041 | NiCrCoMo + Ti, Al | 870 °C | High strength at temperature; sheet and forged parts |
| Nimonic 80A | UNS N07080 | NiCr + Ti, Al | 815 °C | Age-hardenable; valve and turbine components |
Which one to ask for
- 718 — the default when the part needs strength after ageing and the service is around 650–700 °C. Weldable, and the most available.
- X-750 — where the part is a spring or a fastener and relaxation matters more than ultimate strength.
- Waspaloy / Rene 41 — where 718 runs out of temperature and the part still has to carry load.
- 625 — where the service is corrosive as well as hot, so the alloy choice is driven by chemistry rather than temperature.
- 600 — where the part is a fixture and oxidation resistance matters more than strength.
What appears on the certificate
| Composition | Melt analysis, by element |
| Condition | Solution annealed, or solution annealed and aged |
| Mechanical | Tensile, yield, elongation, hardness, reduction of area |
| Grain size | On request, where the specification calls for it |