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.
Inconel 718 and Inconel X-750 are two widely used nickel-based superalloys. Both are known for their exceptional high-temperature performance, but they differ in composition, mechanical strength, and ideal applications. Understanding their differences, benefits, and applications can help industries choose the right material for their needs.
This article provides a detailed comparison of Inconel 718 vs Inconel X-750, covering chemical composition, mechanical properties, performance, cost considerations, and industry applications to help engineers, designers, and buyers select the right material.
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
While both alloys are nickel-chromium-based, Inconel 718 contains niobium and molybdenum, which enhance its strength, whereas X-750 relies more on aluminum and titanium for precipitation hardening.
| 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 |
Inconel 718 outperforms X-750 in tensile strength and oxidation resistance, making it a better choice for aerospace turbines. However, X-750 exhibits excellent creep resistance, which is critical for long-term, high-temperature mechanical applications such as springs and fasteners.
Physical Properties: Inconel 718 and Inconel X-750
| Property | Inconel 718 | Inconel X-750 |
|---|---|---|
| Density (g/cm³) | 8.19 | 8.28 |
| Melting Range (°C) | 1260 – 1336 | 1390 – 1430 |
| Thermal Conductivity (W/m·K, at 20°C) | ~11.4 | ~11.4 |
| Electrical Resistivity (µΩ·m, at 20°C) | ~1.29 | ~1.29 |
| Elastic Modulus (GPa) | 200–210 | 207 |
Insight:
Inconel 718 has a slightly lower density and broader melting range, which supports better weldability and machinability.
Inconel X-750 has a higher melting point, which enhances thermal stability in certain high-temperature applications.
Main Standards and Specifications
Both Inconel 718 and Inconel X-750 comply with international standards to ensure quality and traceability:
Inconel 718
ASTM B637 (Bars, Forgings)
ASTM B670 (Plates, Sheets, Strips)
AMS 5662 / AMS 5663 (Aerospace Specifications)
ISO 15156 / NACE MR0175 (Oil & Gas Applications)
Inconel X-750
ASTM B637 (Bars, Forgings)
ASTM B670 (Plates, Sheets, Strips)
AMS 5667 / AMS 5668 (Aerospace & High-Temperature Applications)
MIL-N-6856 (Military Specifications)
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.
Machinability & Weldability
718: Easier to machine and weld compared to most nickel alloys.
X-750: More difficult to machine, weldability is limited due to risk of cracking.
Cost of Inconel 718 and Inconel X-750
While Inconel 718 generally excels in tensile strength, corrosion resistance, and machinability, the overall price difference between Inconel 718 and Inconel X-750 is typically insignificant. This is partly due to Inconel 718’s lower nickel content and higher iron content, which reduces raw material costs, and partly due to its widespread industrial applications, which ensure ample supply and low marginal costs.
Therefore, if your project requires a cost-effective alloy with balanced properties and broad applicability, Inconel 718 is generally the preferred choice. However, if your design specifically requires excellent long-term creep resistance at elevated temperatures, Inconel X-750 may still be a better choice.
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.
These alloys cannot be directly substituted. When selecting suitable materials, operating temperature, mechanical load, environmental factors, and life cycle costs should be considered.
Supported Products (Available Forms)
At Huaxiao Metal, both Inconel 718 and Inconel X-750 are available in a variety of forms to meet different industrial needs:
Sheet & Plate (cold rolled & hot rolled)
Bar & Rod (round, square, hexagonal)
Tube & Pipe (seamless and welded)
Wire & Strip (for springs, fasteners, electrical applications)
Forgings & Customized Parts (according to drawings or specifications)
This helps engineers, manufacturers, and buyers easily integrate these alloys into different projects, from aerospace turbines to nuclear power components.
FAQ
What are the main differences between Inconel 718 and Inconel X-750?
Inconel 718 offers superior high-temperature strength and good corrosion resistance, making it suitable for aerospace and gas turbines. Inconel X-750, while slightly less strong at high temperatures, excels in creep resistance and is widely used in springs, fasteners, and nuclear reactors.
Which alloy is more cost-effective, Inconel 718 or X-750?
Inconel 718 is generally more cost-effective due to its balance of strength, corrosion resistance, and machinability. X-750 may be preferred when long-term creep resistance at high temperatures is critical.
Can Inconel 718 and X-750 be used interchangeably?
Not always. Although both belong to the Inconel family, their performance differs under specific conditions. Engineers typically select 718 for aerospace/turbine applications and X-750 for high-temperature mechanical parts.
What industries commonly use Inconel 718 and X-750?
Inconel 718 is widely used in aerospace, oil & gas, and power generation. Inconel X-750 is common in nuclear reactors, jet engines, and high-temperature springs.
In Conclusion:
In summary, both Inconel 718 and Inconel X-750 are excellent high-performance alloys, but they meet different needs. Inconel 718 offers a more cost-effective balance between strength and corrosion resistance, while X-750 excels in long-term creep resistance. Your choice should depend on the operating temperature, mechanical stress, and application environment.
Both Inconel 718 and Inconel X-750 are exceptional materials, but their unique compositions and properties make them suited for different applications. Inconel 718 excels in high-stress, corrosive environments, while Inconel X-750 is unbeatable in high-temperature, creep-resistant conditions.
Huaxiao Metal has been focusing on the production and manufacturing of nickel alloys for more than ten years. We are a major global supplier of corrosion-resistant alloys and other high-temperature alloy metals. We have a professional technical team and after-sales service, so we can provide high-quality Hastelloy, Incoloy, Inconel, Monel, duplex stainless steel, and other alloy materials. These materials are available in wire, bar, plate, pipe, flange, forging and other forms to meet customer needs.
When choosing the right material for your project, consider the operating conditions, required mechanical properties, and cost-effectiveness. If you’re still unsure, contact our team at Huaxiao Metal for expert advice on selecting the perfect alloy for your needs.
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