Inconel is a trademarked name developed in the 1940s by the International Nickel Company (INCO) (now owned by Special Metals Corporation). It was created to address the need for materials that could withstand high temperatures, corrosion, and oxidation in jet engines.
- First Application: Jet engine components during World War II
- Development: As aerospace, nuclear power, and chemical industries advanced, more Inconel grades were developed to meet diverse extreme-environment demands.
What Is Inconel Alloy?
Inconel refers to a family of nickel-based high-temperature alloys, typically composed of:
- Nickel (Ni): 50–75%
- Chromium (Cr): Enhances oxidation and corrosion resistance
- Iron (Fe): Some Inconel grades are nickel-iron based
- May also contain molybdenum, cobalt, aluminum, titanium, niobium, and others to improve strength and stability
Key Characteristics:
- Exceptional oxidation and corrosion resistance
- Maintains strength and stability at high temperatures
- Resistant to pressure, fatigue, and creep
- Often used in extreme environments (above 1000°C)
Common Inconel Alloy Grades
| Alloy Grade | UNS Number | Key Characteristics |
| Inconel 600 | N06600 | Versatile; oxidation and corrosion resistant; suitable for medium to high temperatures |
| Inconel 601 | N06601 | Enhanced oxidation resistance; ideal for heat treatment furnaces |
| Inconel 625 | N06625 | Molybdenum-rich; excellent corrosion resistance; used in chemical and marine engineering |
| Inconel 718 | N07718 | Precipitation hardenable; high strength; used in aerospace and turbine blades |
| Inconel X-750 | N07750 | Creep and corrosion resistant; commonly used in nuclear industry |
| Inconel 690 | N06690 | Excellent high-temperature water corrosion resistance; used in nuclear steam generators |
| Inconel 751 / 725 / 617 | N07751, etc. | Specialty grades for nuclear fuel, high-temp chemical systems |
| Alloy Grade | Main Chemical Composition (wt.%) | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
| Inconel 600 | Ni ≥ 72, Cr 14–17, Fe 6–10 | 655 | 240 | ≥ 30 |
| Inconel 601 | Ni ≥ 58, Cr 21–25, Al 1–1.7 | 690 | 275 | ≥ 30 |
| Inconel 625 | Ni ≥ 58, Cr 20–23, Mo 8–10, Nb+Ta 3.15–4.15 | 827 | 414 | ≥ 30 |
| Inconel 718 | Ni 50–55, Cr 17–21, Fe balance, Nb+Ta 4.75–5.5, Mo 2.8–3.3, Ti, Al | 1240 | 1035 | ≥ 12 |
| Inconel X-750 | Ni ≥ 70, Cr 14–17, Fe 5–9, Ti 2.25–2.75, Al 0.4–1.0 | 965 | 725 | ≥ 18 |
| Inconel 690 | Ni ≥ 58, Cr 27–31, Fe 7–11 | 620 | 240 | ≥ 30 |
Applications of Inconel Alloy
| Industry | Example Applications |
| Aerospace | Jet engine blades, combustion chambers, turbine casings |
| Chemical | Heat exchangers, reactors, tanks, piping systems |
| Marine | Seawater heat exchangers, submarine components |
| Nuclear | Steam generators, control rod drive mechanisms |
| Automotive | High-performance exhaust systems (e.g., in racing) |
| Energy | Gas turbines, power plant boilers |
Is Inconel Magnetic?
- Most Inconel alloys are non-magnetic in the annealed state
- Some (like 600, 625) may become slightly magnetic after cold working or exposure to high temperatures
- Inconel 718 can show some magnetism due to its complex alloying
Machinability of Inconel
Inconel is widely regarded as a difficult-to-machine alloy due to:
- High strength at elevated temperatures, which leads to rapid tool wear
- Tendency to work-harden during machining
- Low thermal conductivity, concentrating heat at the cutting edge
Machining Tips:
- Use rigid machines and setups
- Prefer carbide or coated tools
- Apply low cutting speeds with high feed rates
- Use aggressive coolant flow, typically water-based
- Use EDM, grinding, or laser cutting for complex shapes or fine tolerances
Common Type Inconel Alloys
Inconel alloys are extensively used in aerospace, chemical processing, power generation, and marine industries due to their superior high-temperature strength, oxidation resistance, and corrosion resistance. Below is a summary of common product types and their associated standards:
| Product Type | Standard Number | Description / Applicable Grades |
| Pipes & Tubes | ASTM B167 (Seamless), ASTM B751 (Welded), ASTM B775 (Welded & Annealed) | Used for Inconel 600, 601, 625, 690; excellent in heat exchangers |
| Bars & Rods | ASTM B166 (Hot-Rolled/Forged), ASTM B637 (Age-Hardened 718/X-750) | Inconel 600, 625, 718, X-750 rods for high-stress environments |
| Plates & Sheets | ASTM B168 (600/601), ASTM B443 (625), ASTM B670 (718), AMS 5540 (X-750) | Flat-rolled products used in aerospace, furnaces, and marine |
| Flanges | ASTM B564 (Nickel Alloy Forgings including Flanges, Rings, Discs) | Forged flanges of Inconel 600, 625, 718, X-750, 690 |
| Pipe Fittings | ASTM B366 (Wrought Fittings), ASME B16.9 (Butt-Weld Fittings) | Elbows, reducers, tees, caps for high-temp/pressure systems |
| Fasteners | ASTM F2281 (Inconel 718 Fasteners), ASTM B637 (Mechanical Fastener Stock) | Bolts, screws, and nuts for aircraft, turbines, reactors |
| Welding Materials | AWS A5.14 / ERNiCr-3 (625, 600), AWS A5.14 / ERNiFeCr-2 (718) | Used for welding Inconel 600/625/718 alloys |
| Forgings | ASTM B564 | Forged rings, flanges, shafts, turbine discs, etc. |
| Custom Machined Parts | No unified standard – typically follow ASTM base alloy + ASME machining standards | Valve seats, nozzle blocks, hot-section components |
Inconel vs Titanium
Inconel is more suitable for high-temperature, high-pressure environments, while Titanium is lighter and ideal for structural or biomedical applications.
| Comparison Item | Inconel | Titanium |
| Base Composition | Nickel-based alloy | Pure titanium or titanium alloy |
| Density | High (~8.4 g/cm³) | Low (~4.5 g/cm³) |
| Strength | Very high, especially at high temps | Moderate; strength drops at high temps |
| Corrosion Resistance | Excellent (acid, alkali, seawater) | Excellent (seawater, biomedical) |
| Temperature Range | Up to and above 1000°C | Generally below 600°C |
| Machinability | Difficult | Relatively easier |
| Cost | Very expensive | Expensive |
Inconel vs Monel
Inconel excels in high-temperature resistance; Monel is superior in seawater and acid resistance.
| Comparison Item | Inconel Alloy | Monel Alloy |
| Base Composition | Nickel + Chromium + Iron + Molybdenum | Nickel + Copper + small amounts of Fe, Mn |
| Temperature Tolerance | Very high (above 1000°C) | Moderate (up to ~550°C) |
| Corrosion Resistance | Excellent in oxidizing, acidic, alkaline, chloride conditions | Especially resistant to seawater and hydrofluoric acid |
| Strength | Outstanding at high temperatures | Good at room temperature; drops at high temp |
| Machinability | Difficult | Relatively easier |
| Typical Uses | Jet engines, nuclear systems | Marine engineering, chemical pumps, valves |
Contact MT.BOLTS
MT.BOLTS specializes in the manufacturing and supply of industrial fasteners including screws, bolts, nuts, and washers. Our products conform to international standards (ANSI / ASTM / DIN / ISO / JIS) and are available in various materials, dimensions, and surface finishes.
Contact us today to learn more about fasteners and to procure high-quality products. Our technical team is ready to provide expert support and custom selection solutions.
