AMS 5663 Inconel 718, also known as Alloy 718 or UNS N07718, is a high-strength, corrosion-resistant nickel-chromium alloy, ideal for many industries due to its unique properties. This article will explore the characteristics, applications, and history of Inconel 718, providing a comprehensive understanding of this versatile alloy.
What is Inconel 718?
Inconel 718 is a nickel-chromium alloy that contains significant amounts of iron, columbium, and molybdenum, along with lesser amounts of aluminum and titanium. It is characterized by high strength, good ductility, oxidation resistance at high temperatures, and excellent cryogenic properties, making it ideal for applications involving exposure to cryogenic temperatures.
Key Properties and Characteristics of Alloy 718
Inconel 718 is known for its unique set of properties, including:
- High Strength: It maintains its strength at high temperatures and has excellent cryogenic properties, making it ideal for applications in extreme conditions.
- Corrosion Resistance: The nickel-chromium base provides exceptional resistance to a wide range of corrosive environments.
- Excellent Weldability: This characteristic is crucial for achieving the desired precipitation-hardened state through furnace cool methods. Inconel 718 can be readily worked and age-hardened, allowing it to be welded in fully aged conditions.
Chemical Composition of Nickel Alloy 718
Inconel 718’s chemical composition includes a balance of multiple elements:
| Chemical Element | Minimum % of a specific element can significantly influence the material’s hardness. of a specific element can significantly influence the material’s hardness. | Maximum % |
| Nickel (Ni), a key component of Inconel 718, contributes to the alloy’s outstanding corrosion resistance and is fundamental to its classification as a special metal. | 50 | 55 |
| Chromium (Cr) | 17 | 21 F |
| Iron (Fe) bar | – This can be observed following the solution annealing and cool down phase. | Bal cool |
| Molybdenum (Mo) | 2.8 | 3.3 |
| Niobium (Nb+Ta) | 4.75 | 5.5 |
| Titanium (Ti) | 0.65 HRC is a measure of hardness that might be specified for materials in high strength bolting solutions to ensure they meet the necessary hardness specifications. | 1.15 F |
| Aluminum (Al) | 0.2 | 0.8 |
Mechanical Properties
Inconel 718 exhibits excellent mechanical properties, including high tensile strength and yield strength, benefiting greatly from solution annealing and age hardening treatments. These properties are maintained from cryogenic to elevated temperatures.
Varieties of Inconel 718
Several conditions of Inconel 718 are available, each with unique characteristics:
- AMS 5662: This is the rawest and softest condition of Inconel 718. It can be heat treated into AMS 5663 for specific outcomes.
- AMS 5663: This is achieved by heat treating AMS 5662. Certain outcomes such as optimum impact properties or optimum tensile and creep-rupture properties can be achieved through this process, including annealing and age-hardening treatments to improve material hardness.
- AMS 5664: This has a more complicated forming process and offers higher tensile and yield strength, along with specific grain size restrictions.
- NACE MR-01-75: requiring materials to undergo specific hardness testing and heat treatment processes to meet standard specifications. This version is produced in accordance with API (American Petroleum Institute) standards and offers a different range of characteristics.
Technical Applications of Inconel 718
Inconel 718 is used in various industries because of its unique properties: including its ability to be precipitation-hardened and its excellent weldability after furnace cool treatment.
- Aerospace: employing alloys that undergo specific heat treatment processes to enhance their hardness and resistance characteristics for applications like jet engines. It provides the vital strength aircrafts require, withstanding the intense heat of the afterburners and the freezing temperatures experienced at high altitude.
- Chemical processing: Its high strength and corrosion resistance make it suitable for various applications in the chemical processing industry.
- Oil and Gas: Inconel 718 is the preferred material for many oil, offshore, and OEM applications, particularly for components like fasteners, due to its high strength and resistance to harsh environmental conditions.
Inconel 718 in the Aerospace Industry
Inconel 718 plays a vital role in the aerospace industry. It is used in the construction of various components such as:
- Cryogenic storage tanks
- Downhole shafting, especially when manufactured from Inconel 718, benefits from the alloy’s compatibility with special metals and its ability to withstand harsh environments.
- Gas turbine components require materials that can endure high temperatures and stresses, such as Inconel 718, which may also be specified according to ASTM standards for these applications.
- High strength bolting solutions, typically involving materials that have undergone specific heat treatments to meet the necessary hardness specifications, often require a comprehensive understanding of ASTM standards and the use of special metals.
- Jet engines, which often utilize parts made from materials that have been annealed to improve their hardness and resistance to high temperatures.
- Nuclear fuel element spacers
- Pump parts
- Pump shafts, often fabricated from alloys meeting ASTM standards, are critical for ensuring the reliable operation of industrial pumping systems.
- Rocket motors, often constructed from Inconel 718, which is designated as UNS N07718 or material number 2.4668, employ this alloy for its strength at cryogenic temperatures.
- Thrust reversers, which are critical in aerospace applications, require materials like Inconel 718 that have undergone forging and heat treatment to ensure optimal performance.
Machinability of Inconel 718
Inconel 718 can be machined using conventional production methods at satisfactory rates. The alloy work hardens rapidly, generates high heat during cutting, welds to the cutting tool surface, and offers high resistance to metal removal due to its high shear strengths. Proper heat treatment is essential to mitigate these challenges.
Conclusion
Inconel 718 is a versatile alloy with a wide range of applications. Its high strength, corrosion resistance, and excellent weldability make it a choice material in various industries, from aerospace to oil and gas. Understanding its properties and uses can help businesses make informed decisions about its application.
Remember to consult with a materials expert or engineer when considering Inconel 718 for your specific application to ensure it meets your requirements and specifications, especially concerning its AMS 5596 specification for sheet and plate forms.
