In the world of high-performance engineering materials, nickel-based alloys play an irreplaceable role in demanding environments such as oil and gas, chemical processing, and aerospace. Among them, Alloy N09935, Alloy 718, Alloy 925, and Alloy 945 are four important grades often compared by engineers and purchasing specialists.
This article from SASAALLOY provides a detailed analysis of the chemical composition, mechanical properties, corrosion resistance, and application differences of these alloys—helping you make an informed choice for your specific project.
1. Overview of Each Alloy
1.1 Alloy N09935 (UNS N09935)
Alloy N09935 is a nickel-iron-chromium alloy with carefully balanced additions of molybdenum, copper, niobium, and titanium. It is designed to combine excellent corrosion resistance with high strength, even under sour-gas service conditions (H₂S environments). The alloy is often used in oilfield tubulars, downhole components, and chemical process systems where both mechanical integrity and corrosion resistance are critical.
It conforms to ASTM B649 and meets NACE MR0175 / ISO 15156 requirements for sour-service applications.
1.2 Alloy 718 (UNS N07718)
Alloy 718, also known as Inconel 718, is a nickel-chromium alloy strengthened by additions of niobium, titanium, and aluminum. It is a precipitation-hardening superalloy primarily used in aerospace turbines, power generation, and high-temperature bolts and fasteners.
Its main advantage lies in exceptional strength up to about 700°C, combined with good weldability and oxidation resistance.
1.3 Alloy 925 (UNS N09925)
Alloy 925 is a precipitation-hardened nickel-iron-chromium alloy that contains additions of molybdenum, copper, titanium, and aluminum. It offers a strong combination of high strength and corrosion resistance in various aggressive environments including sulfides, chlorides, and carbon dioxide.
The alloy is often used in downhole oil tools, tubular components, and marine fasteners, and it is also compliant with NACE MR0175 / ISO 15156.
1.4 Alloy 945 / 945X (UNS N09945)
Alloy 945 (and its variant 945X) is a super-strength nickel-iron-chromium alloy developed as an improved version of Alloy 925, with optimized levels of niobium and molybdenum to enhance both strength and stress-corrosion-cracking resistance.
It is particularly suitable for completion hardware, downhole hangers, and wellhead components used in sour service and deep-well environments.
2. Chemical Composition Comparison
| Element | Alloy N09935 | Alloy 718 | Alloy 925 | Alloy 945 |
|---|---|---|---|---|
| Nickel (Ni) | 35–40 | 50–55 | 42–46 | 44–47 |
| Chromium (Cr) | 20–23 | 17–21 | 19.5–22.5 | 21–23 |
| Iron (Fe) | Balance | Balance | Balance | Balance |
| Molybdenum (Mo) | 3.5–4.5 | 2.8–3.3 | 2.5–3.5 | 3.0–4.0 |
| Copper (Cu) | 1.5–2.5 | — | 1.5–3.0 | 1.0–1.8 |
| Niobium + Tantalum (Nb+Ta) | 0.6–1.0 | 4.75–5.5 | 0.5–1.0 | 2.5–3.0 |
| Titanium (Ti) | 0.2–0.6 | 0.65–1.15 | 1.9–2.4 | 1.0–1.5 |
| Aluminum (Al) | 0.1–0.4 | 0.2–0.8 | 0.1–0.5 | 0.2–0.6 |
From this table, it’s clear that Alloy 718 has much higher niobium and titanium contents for precipitation hardening, while Alloy 925 and 945 include more copper for enhanced resistance to reducing acids and brines. Alloy N09935, however, is balanced to achieve stable corrosion performance with moderate strength—making it ideal for mixed environments with H₂S and CO₂.
3. Mechanical Properties
| Property | Alloy N09935 | Alloy 718 | Alloy 925 | Alloy 945 |
|---|---|---|---|---|
| Yield Strength (MPa) | 690–930 | 1030–1275 | 690–860 | 965–1030 |
| Tensile Strength (MPa) | 930–1100 | 1240–1380 | 930–1030 | 1100–1170 |
| Elongation (%) | 30–40 | 12–20 | 25–35 | 20–30 |
| Hardness (HRC) | 25–32 | 35–44 | 28–32 | 32–38 |
Alloy 718 stands out for the highest strength, suitable for extreme mechanical load conditions such as turbine discs and high-pressure bolts.
Alloy N09935 and 925 are more ductile and easier to machine or form.
Alloy 945 offers an excellent middle ground — higher strength than 925 but better ductility than 718, especially after aging treatment.
4. Corrosion Resistance Comparison
4.1 Resistance to H₂S and CO₂ Environments
Alloy N09935, Alloy 925, and Alloy 945 are all approved for NACE MR0175 / ISO 15156 sour service, while Alloy 718 generally requires special qualification for such use.
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Alloy N09935: Exceptional resistance to sulfide stress cracking and pitting in sour wells.
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Alloy 925: Good resistance but may show localized corrosion in high-chloride, high-temperature conditions.
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Alloy 945: Superior to 925 due to optimized composition and microstructure.
4.2 Chloride-Induced Pitting and Crevice Corrosion
Thanks to higher chromium and molybdenum levels, Alloy N09935 and 945 resist chloride pitting better than Alloy 925.
Alloy 718, while oxidation-resistant, is not ideal for seawater or chloride-rich brines.
4.3 Acid and Chemical Media
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Alloy 925 and 945: Handle hydrochloric acid and sulfuric acid better due to copper content.
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Alloy N09935: Excellent in mixed acid/chloride environments typical of chemical process plants.
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Alloy 718: Designed more for high-temperature oxidation, not for reducing acids.
6. Fabrication and Heat Treatment
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Alloy N09935 is readily machinable and weldable, similar to Alloy 625, with standard aging treatments to achieve target mechanical properties.
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Alloy 718 requires precise heat treatment cycles (solution + double aging) to activate gamma-prime strengthening.
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Alloy 925 uses precipitation hardening with titanium and aluminum to achieve moderate strength.
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Alloy 945 combines controlled forging, solution annealing, and aging to deliver high yield strength and superior corrosion resistance simultaneously.
For many oilfield equipment manufacturers, the choice between these alloys depends on the balance between cost, strength, and corrosion resistance—an area where SASAALLOY provides technical guidance and material selection support.
7. Cost and Availability
In general price order (lowest to highest):
Alloy 925 < Alloy N09935 < Alloy 945 < Alloy 718
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Alloy 925: Most economical for moderate sour-service tools.
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Alloy N09935: Offers excellent corrosion strength ratio—often replacing Alloy 625 or 718 in oilfield parts.
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Alloy 945: Premium cost but ensures superior sour-service life.
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Alloy 718: High-temperature alloy; cost influenced by aerospace specifications and strict heat-treatment control.
8. Why Choose Alloy N09935?
Engineers increasingly select Alloy N09935 as a next-generation alternative to 925 and 718 in oil and gas applications. The reasons include:
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Balanced Strength and Ductility: High yield strength (≈900 MPa) without excessive brittleness.
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Excellent Sour-Gas Resistance: Fully compliant with NACE MR0175 / ISO 15156.
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Superior Pitting Resistance: Ideal for H₂S + CO₂ + Cl⁻ combined environments.
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Good Fabrication Characteristics: Can be easily formed and welded compared with higher-strength superalloys.
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Thermal Stability: Performs well up to 650 °C in continuous service.
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Cost-Effective: Lower nickel content than Inconel 718 while maintaining strong mechanical integrity.
These features make it a preferred material for oilfield completion tools, chemical reactors, and fasteners that demand durability under aggressive service conditions.
9. Practical Selection Guide
| Requirement | Recommended Alloy |
|---|---|
| High strength above 700 °C | Alloy 718 |
| Maximum sour-service resistance | Alloy 945 |
| Balanced corrosion and strength | Alloy N09935 |
| Cost-sensitive projects | Alloy 925 |
| Aerospace fasteners | Alloy 718 |
| Deep-well completion equipment | Alloy 945 / N09935 |
Selecting the right alloy depends on environmental conditions (temperature, pressure, gas composition) and desired lifespan. Consulting metallurgical specialists ensures that each project achieves both technical safety and cost efficiency.
10. SASAALLOY – Your Reliable Nickel Alloy Partner
SASAALLOY specializes in the supply of high-performance nickel-based alloys including Alloy N09935, 718, 925, and 945, offering comprehensive technical support, customized sizes, and certified quality under ASTM, ASME, and NACE standards.
With years of experience serving the oil and gas, chemical, and marine industries, SASAALLOY ensures:
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Material traceability and 3.1/3.2 certificates
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PMI testing and NACE HIC/SSC qualification
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Precision machining, heat treatment, and export packaging
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Fast global delivery from stock and production
Whether you are designing new equipment or replacing legacy materials, SASAALLOY’s engineering team will help you select the optimal alloy grade for long-term reliability and performance.
11. Conclusion
Although Alloy N09935, 718, 925, and 945 share nickel-iron-chromium foundations, each alloy serves a distinct purpose:
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718 — unmatched for high-temperature strength.
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925 — economical and reliable for moderate sour service.
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945 — premium alloy with top-tier corrosion resistance.
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N09935 — the most balanced choice, offering strong mechanical performance and superior resistance in aggressive chemical and oilfield environments.
As industries continue to push boundaries in deep-well exploration and chemical processing, Alloy N09935 is rapidly emerging as the smart, cost-effective alternative for next-generation equipment.
For more details, technical datasheets, or material availability, contact SASAALLOY today — your trusted global supplier of nickel-based alloys.
Post time: Oct-29-2025