In the realm of high-performance nickel-based alloys, three alloys stand out for their exceptional strength, heat resistance, and corrosion resistance-Nickel 716, Inconel 718, and Alloy 625. All three materials are meticulously designed to deliver superior performance under extreme stress, high temperatures, and corrosive environments, but their mechanical properties, heat treatment characteristics, and optimal application areas differ.
As industries such as aerospace, energy, marine, and oil and gas continue to push the limits of material performance, understanding the differences between these alloys is crucial for engineers and procurement experts.
This article provides a detailed comparison of Nickel 716 round bars, Inconel 718, and Alloy 625, highlighting their chemical composition, mechanical properties, corrosion resistance, and industrial applications, and emphasizing how Gnee Steel offers high-quality materials designed for superior reliability and consistency.
Comparison of nickel alloy 716 vs Inconel 718 and alloy 625 round bars
Comparison of nickel alloy 716 vs. Inconel 718 and alloy 625 round bars
Nickel alloy 716 round bars (commonly referred to as Alloy 625+ or UNS N07716) combine high strength and corrosion resistance, serving as a bridge between the superior strength of Inconel 718 round bars and the high corrosion resistance of Alloy 625 bars.
In terms of bar form, Alloy 716 bars are designed to provide similar corrosion resistance to Alloy 625 round bars while maintaining the high strength of Inconel 718 round bars.
What are the limitations of the Inconel 718?
However, machining the Inconel 718 is an extremely challenging process. High power requirements, short tool life, low cutting speeds, and poor surface finish result in high manufacturing costs and low production efficiency.
Overview of alloy 716 And 718 and 625 alloys
| Alloy | Type | Key Features | Typical Applications |
|---|---|---|---|
| Nickel Alloy 716 | Precipitation-hardened nickel-chromium-iron alloy | High strength, superior oxidation resistance, excellent creep performance up to 700°C | Aerospace, turbines, oil & gas, marine |
| Inconel 718 | Precipitation-hardened nickel-based superalloy | Excellent strength up to 650°C, good weldability and fatigue resistance | Jet engines, gas turbines, power generation |
| Alloy 625 | Solid-solution strengthened nickel-chromium-molybdenum alloy | Outstanding corrosion resistance, ductility, and toughness | Chemical plants, seawater systems, marine and offshore use |
All three alloys use nickel as a base, but their strengthening mechanisms and performance vary depending on the balance of elements such as niobium, molybdenum, and chromium.
Comparison of chemical compositions of alloys 716, 718, and 625 Alloy Bar
| Element | Nickel Alloy 716 (%) | Inconel 718 (%) | Alloy 625 (%) |
|---|---|---|---|
| Nickel (Ni) | 50.0 – 55.0 | 50.0 – 55.0 | ≥ 58.0 |
| Chromium (Cr) | 17.0 – 21.0 | 17.0 – 21.0 | 20.0 – 23.0 |
| Iron (Fe) | Balance | Balance | ≤ 5.0 |
| Molybdenum (Mo) | 2.8 – 3.3 | 2.8 – 3.3 | 8.0 – 10.0 |
| Niobium (Nb) + Tantalum (Ta) | 4.8 – 5.5 | 4.75 – 5.50 | 3.15 – 4.15 |
| Titanium (Ti) | 0.6 – 1.15 | 0.65 – 1.15 | ≤ 0.4 |
| Aluminum (Al) | 0.2 – 0.8 | 0.2 – 0.8 | ≤ 0.4 |
| Cobalt (Co) | ≤ 1.0 | ≤ 1.0 | ≤ 1.0 |
| Carbon (C) | ≤ 0.08 | ≤ 0.08 | ≤ 0.10 |
Strengthening Mechanisms
Ni-based Alloy 716
Strengthened through the controlled precipitation of γ′ (Ni₃(Al,Ti)) and γ″ (Ni₃Nb) phases during aging. These phases hinder dislocation movement, resulting in excellent strength and creep resistance at high temperatures.
Inconel 718
Similarly strengthened through the precipitation of γ′ and γ″ phases, but with slightly lower phase stability above 650°C. It exhibits excellent fatigue resistance and weldability, making it an ideal material for aerospace fasteners and jet engine components.
Alloy 625
Strengthened by the solid solution of molybdenum and niobium in the nickel matrix. While it possesses excellent corrosion resistance and ductility, its high-temperature strength is lower than that of 716 or 718.
Comparison of mechanical properties of nickel-based alloys 716, Inconel 718, and Alloy 625 Bar
| Property | Nickel Alloy 716 | Inconel 718 | Alloy 625 |
|---|---|---|---|
| Tensile Strength (MPa) | 1250 – 1500 | 1200 – 1350 | 830 – 950 |
| Yield Strength (MPa) | 900 – 1100 | 850 – 1000 | 450 – 620 |
| Elongation (%) | 12 – 20 | 15 – 25 | 30 – 40 |
| Hardness (HB) | 330 – 380 | 320 – 360 | 200 – 240 |
| Density (g/cm³) | 8.19 | 8.19 | 8.44 |
| Operating Temperature (°C) | Up to 700 | Up to 650 | Up to 600 |
Corrosion resistance and oxidation resistance of nickel-based alloys 716, Inconel 718, and Alloy 625 Bar
| Type of Resistance | Nickel Alloy 716 | Inconel 718 | Alloy 625 |
|---|---|---|---|
| General Corrosion | Excellent | Excellent | Outstanding |
| Pitting and Crevice Corrosion | Very Good | Good | Excellent |
| Oxidation Resistance (up to 700°C) | Excellent | Very Good | Good |
| Sulfidation Resistance | Excellent | Very Good | Very Good |
| Stress Corrosion Cracking (SCC) | Excellent | Excellent | Excellent |
Nickel-based alloys 716, Inconel 718, and Alloy 625: Performance at high temperatures
Nickel Alloy 716 maintains high strength and oxidation resistance up to 700°C, making it ideal for continuous high-heat service such as turbine blades, fasteners, and exhaust systems.
Inconel 718 performs well up to 650°C, suitable for aircraft engines and gas turbines where fatigue strength and weldability are crucial.
Alloy 625 is typically limited to 600°C for mechanical applications but excels in chemical plants and offshore systems due to its corrosion protection.
Industrial applications of nickel-based alloys 716, Inconel 718, and Alloy 625 Bar
| Industry | Nickel Alloy 716 | Inconel 718 | Alloy 625 |
|---|---|---|---|
| Aerospace | Turbine shafts, compressor discs, bolts | Engine casings, turbine wheels | Ducts and bellows |
| Oil & Gas | Subsea valves, completion tools | Drilling tools, wellhead equipment | Seawater piping, risers |
| Power Generation | Steam turbines, nuclear components | Gas turbine parts | Heat exchangers, condensers |
| Chemical Processing | High-pressure reactors | Acid-resistant components | Reactors, distillation columns |
| Marine Engineering | Offshore connectors | Turbine housings | Pumps, fittings, flanges |
Gnee Steel is a professional manufacturer of various nickel-based alloys, including Nickel 201, Nickel 202, Hastelloy C-276, Hastelloy C-22, Hastelloy B, Hastelloy C-4, Inconel Alloy 600, Inconel 625, Inconel 718, Inconel X-750, Incoloy Alloy 800, Incoloy 800H/HT, Incoloy 825, Monel Alloy 400, Monel K500, and high-temperature alloys. We specialize in the production and sales of alloy materials. Gnee Steel's products are widely used in aerospace, chemical, power, automotive, and nuclear energy industries, and we can provide customized alloy material solutions according to customer needs. For alloy material price inquiries or to request customized alloy material solutions, please feel free to contact us at ru@gneesteelgroup.com for a quote.