Inconel alloys are known for their outstanding performance in high-temperature and corrosive environments. Among the most popular are Inconel 718 vs Inconel X-750, both nickel-chromium alloys offer unique properties that make them suitable for demanding industries such as aerospace, power generation, and chemical processing. Understanding their differences, benefits, and applications can help industries choose the right material for their needs.
What Is Inconel 718?
Inconel 718 is a nickel-based superalloy known for its high strength, corrosion resistance, and excellent weldability. It is precipitation-hardenable, meaning its mechanical properties can be enhanced through heat treatment.
- Temperature Range: Performs well in temperatures ranging from -250°C to 700°C.
- Corrosion Resistance: Outstanding resistance to oxidation, pitting, and stress-corrosion cracking, even in harsh environments.
- Mechanical Strength: High tensile and yield strength due to its niobium content.
- Applications: Commonly used in aerospace turbines, gas turbines, nuclear reactors, and oil and gas extraction.
What Is Inconel X-750?
Inconel X-750 is another nickel-based alloy that excels in high-temperature environments. It is also precipitation-hardenable but contains more aluminum and titanium than Inconel 718, contributing to its strength at elevated temperatures.
- Temperature Range: Performs optimally at temperatures up to 980°C.
- Creep Resistance: Superior resistance to deformation under long-term high-temperature stress.
- Corrosion Resistance: Good resistance to oxidation and chemical corrosion, though slightly less than Inconel 718.
- Applications: Frequently used in jet engines, nuclear reactors, springs, and fasteners.
Inconel 718 vs Inconel X-750: What Are Their Differences?
Chemical Composition: Inconel 718 vs Inconel X-750
Both alloys share a nickel-chromium base but differ in secondary elements that define their performance characteristics:
| Element | Inconel 718 | Inconel X-750 |
|---|---|---|
| Ni | 50-55% | 70% minimum |
| Cr | 17-21% | 14-17% |
| Fe | Bal. | 5-9% |
| Mo | 2.8-3.3% | – |
| Ti | 0.65-1.15% | 2.25-2.75% |
| Al | 0.2-0.8% | 0.4-1% |
| Nb | 4.75-5.5% | – |
| Co | 1% max | 1% max |
Mechanical Properties: Inconel 718 vs Inconel X-750
| Property | Inconel 718 | Inconel X-750 |
|---|---|---|
| Tensile Strength | 1370 MPa | 1100 MPa |
| Yield Strength | 1030 MPa | 780 MPa |
| Elongation | 12-15% | 15-20% |
| Hardness (Rockwell) | B95-C36 | B88-C32 |
Performance in High-Temperature Environments
- Inconel 718:
Inconel 718 is designed for moderate to high-temperature applications but begins to lose mechanical properties above 700°C. Its weldability makes it suitable for fabrications that require precision. - Inconel X-750:
Inconel X-750 can withstand higher temperatures, up to 980°C, with excellent creep resistance. This makes it more suitable for components like turbine blades and nuclear reactor springs, where prolonged exposure to extreme heat is expected.
Corrosion Resistance: Inconel 718 VS Inconel X-750
Both alloys exhibit exceptional corrosion resistance:
- Inconel 718 resists pitting, crevice corrosion, and stress-corrosion cracking more effectively, especially in aqueous and acidic environments. It is the preferred choice for offshore oil and gas applications.
- Inconel X-750 offers excellent resistance to oxidation at high temperatures but is less effective in resisting chemical attacks compared to Inconel 718.
Applications of Inconel 718 and Inconel X-750
Advantages of Inconel 718
- Superior mechanical strength.
- Better weldability.
- Excellent resistance to pitting and stress-corrosion cracking.
Advantages of Inconel X-750
- Better high-temperature performance.
- Excellent creep resistance.
- Ideal for long-term, high-heat exposure applications.
Cost of Inconel 718 and Inconel X-750
Inconel 718 tends to be more expensive due to its higher niobium and molybdenum content, which improves its strength and corrosion resistance. In addition, its superior performance in harsh and corrosive environments has increased demand, especially in industries such as oil and gas, aerospace, and offshore engineering.
Inconel X-750 is generally more affordable compared to Inconel 718. This is because it contains lower levels of expensive elements (such as molybdenum) and relies more on aluminum and titanium for precipitation hardening. Its lower production cost makes it a preferred choice for high-temperature applications where corrosion resistance is less important.
Inconel 718 vs Inconel X-750: Which is Better?
| Criteria | Inconel 718 | Inconel X-750 |
|---|---|---|
| Cost | Higher cost | More affordable |
| Machinability | Easier to machine | More challenging to machine |
| Weldability | Excellent | Less weldable |
| Corrosion Resistance | Superior | Moderate |
| Temperature Resistance | Up to 700°C | Up to 980°C |
| Applications | High-strength, corrosive settings | High-temperature environments |
Choose Inconel 718:
If your application requires high strength, better corrosion resistance, and moderate temperature performance, such as in oil and gas or aerospace fabrications.
Choose Inconel X-750:
If your application involves extremely high temperatures and long-term stress, such as turbines, nuclear reactors, or high-temperature springs.
