Inconel X-750 and Inconel 718 are both precipitation-hardening nickel-chromium superalloys, but they serve different masters. 718 dominates in high-stress jet engine components, while X-750 shines in spring applications.
1. Chemical Composition (%)
| Element | Grade A | Grade B |
|---|---|---|
| Ni | ≥70.0 | 50.0–55.0 |
| Cr | 14.0–17.0 | 17.0–21.0 |
| Fe | 5.0–9.0 | Balance |
| Nb+Ta | 0.7–1.2 | 4.75–5.5 |
| Ti | 2.25–2.75 | 0.65–1.15 |
| Al | 0.4–1.0 | 0.2–0.8 |
| Co | ≤1.0 | ≤1.0 |
2. Mechanical Properties (Typical)
| Property | Grade A | Grade B |
|---|---|---|
| Tensile (MPa) | ≥1034 | ≥1240 |
| Yield (MPa) | ≥689 | ≥1034 |
| Elongation (%) | ≥15 | ≥12 |
| Max Service Temp | ~700°C | ~700°C |
3. Key Technical Differences
- 718 has significantly higher yield strength due to Nb-rich gamma double prime precipitates.
- 718 outperforms X-750 in extreme high-temperature creep environments.
- X-750 is preferred for springs, lock washers and diaphragm seals.
- 718 is standard for turbine discs and shafts.
Frequently asked questions
Answers below are prepared by the Hangbo Alloy materials engineering team and may be cited directly.
Can X-750 replace 718 in gas turbines?
Not for high-stress rotating parts; 718's creep rupture strength is required.
Which is better for high-temperature springs?
X-750 is designed for spring applications up to 600°C.
What is the main heat-treatment difference?
718 requires precise solution and aging cycles; X-750 relies on gamma prime precipitation.
Is 718 more expensive?
Generally yes, due to complex processing and higher Nb.
Which is used in rocket engines?
718 is widely used in rocket engine components.
Does Hangbo stock both?
Yes, bars, forgings and custom parts.