AMS 5702: Composition, Properties, and Uses
In the dynamic world of aerospace and engineering, where precision and performance are paramount, the materials we choose can define…
Imagine a material that stands resilient against the fiercest of flames, unwavering in the most corrosive environments, and enduring the most extreme mechanical stresses. This is the realm of Inconel 702, a remarkable nickel-chromium alloy that has become indispensable in industries where failure is not an option. Whether it’s the searing heat of a jet engine or the relentless conditions inside a furnace, Inconel 702 is engineered to perform where other materials would falter.
This article delves into the fascinating world of Inconel 702, exploring its unique chemical composition, which includes critical elements like aluminum that enhance its high-temperature strength and oxidation resistance. We’ll uncover the alloy’s impressive physical and mechanical properties, shedding light on why it is the material of choice for demanding applications. From aerospace components to industrial machinery, discover the diverse uses of Inconel 702 and how it meets the rigorous standards of various sectors.
Moreover, we’ll provide insights into the technical aspects of working with this alloy, including its machinability and the best practices for heat treatment. Whether you’re an engineer, a manufacturer, or a researcher, this comprehensive guide will equip you with the knowledge needed to harness the full potential of Inconel 702. Join us as we unravel the secrets of this extraordinary material and its pivotal role in advancing technology and industry.
Inconel 702, known by its UNS designation N07702, is a high-performance alloy made of nickel and chromium. This alloy’s significant aluminum content gives it excellent high-temperature stability and resistance to oxidation and corrosion. Inconel 702 is engineered to endure extreme conditions, making it a top choice for various demanding industrial applications.
Inconel 702 is a trademark of Special Metals Corporation. Also known as Alloy 702, its UNS designation N07702 standardizes its identification, ensuring consistency in properties and applications across industries and suppliers.
Inconel 702 is a nickel-based superalloy renowned for its superior heat resistance and strength. Its chemical composition is meticulously designed to enhance these properties. The primary elements in Inconel 702 include:
Nickel forms the base of Inconel 702, making up about 79% of the alloy. It provides essential characteristics like high-temperature strength and oxidation resistance.
Chromium, making up 14.00-17.00% of the alloy, significantly enhances resistance to oxidation and corrosion, allowing the alloy to perform well in harsh environments.
Aluminum, present at 2.75-3.75% (typically around 3.4%), forms a protective oxide layer on the alloy’s surface, crucial for preventing oxidation at high temperatures.
Iron, comprising 1.0-2.0% of the alloy, helps stabilize the alloy and contributes to its overall strength and durability.
Titanium, ranging from 0.25-1.00% (typically 0.7%), strengthens the alloy by forming precipitates that enhance the grain structure, improving high-temperature performance.
Minor elements like silicon (0.2-0.70%), manganese (0.05-1.00%), and carbon (0.04-0.10%) aid in deoxidizing the alloy and enhancing its mechanical properties. Cobalt (up to 1.00%) improves high-temperature strength and oxidation resistance, while sulfur (max 0.010%) and copper (max 0.50%) are kept low to avoid hot cracking and improve corrosion resistance.
The precise balance of these elements ensures that Inconel 702 maintains its strength, oxidation resistance, and structural integrity in demanding high-temperature and corrosive environments, making it ideal for critical applications such as jet engine heat exchangers and furnace components.
Inconel 702 exhibits a density of 8.43 g/cm³ (0.304 lb/in³), providing it with a robust structure suitable for high-performance applications, and a modulus of elasticity in tension of 31.5 x 10³ KSI (215 x 10³ MPa), indicating its ability to deform elastically under stress.
The melting range of Inconel 702 is between 1320°C and 1350°C (2540°F to 2462°F), allowing it to maintain structural integrity and performance at elevated temperatures.
Inconel 702 has an impressive ultimate tensile strength of about 130 KSI (893 MPa) and a yield strength of around 95 KSI (655 MPa), ensuring it can withstand significant mechanical loads without permanent deformation.
The alloy demonstrates a high elongation rate of approximately 35%, allowing it to undergo considerable plastic deformation before fracture, and typically measures around 25-26 HRC on the Rockwell C scale, indicating a good balance between hardness and ductility.
Inconel 702 exhibits excellent fatigue strength, making it ideal for applications involving frequent loading cycles, as it can withstand repeated stress without significant performance degradation.
These combined properties make Inconel 702 a versatile alloy, suitable for demanding industrial applications such as aerospace, power generation, and chemical processing, where its high strength, durability, and ability to perform under extreme temperatures ensure optimal performance and longevity.
Inconel 702 is highly valued for use in jet engine heat exchangers due to its outstanding stability and resistance to oxidation at high temperatures, maintaining structural integrity and performance under extreme conditions. Its excellent fatigue strength ensures it can handle the intense demands of aerospace applications over long periods.
The alloy’s ability to resist oxidation at temperatures up to 2400°F (1316°C) makes it a preferred choice for furnace components. Inconel 702 can endure the harsh conditions within furnaces, where materials are exposed to high temperatures and oxidative environments. Its durability and long service life reduce the need for frequent replacements, improving operational efficiency and lowering maintenance costs.
Inconel 702 is also used in afterburner liners in aerospace engines, where it faces extremely high temperatures and corrosive conditions. The alloy’s high-temperature properties and resistance to thermal fatigue make it ideal for these demanding applications.
In addition to jet engines and afterburner liners, Inconel 702 is utilized in various other aerospace components where high strength, corrosion resistance, and the ability to withstand extreme temperatures are crucial. This includes turbine blades, combustion chambers, and exhaust systems.
In the power generation industry, Inconel 702 is used in high-temperature components such as turbine blades and nuclear reactor heat exchangers. Its high-temperature strength and oxidation resistance ensure reliable performance and longevity in these critical applications.
The alloy’s corrosion resistance makes it ideal for chemical processing facilities, where it is used in equipment exposed to harsh chemicals and high temperatures. Its resistance to oxidation and corrosion ensures the integrity and durability of reactors, heat exchangers, and piping systems.
In oil refineries, Inconel 702 is used in components that must endure high temperatures and corrosive environments. Its durability and resistance to degradation make it a valuable material for catalytic cracking units and distillation columns.
Inconel 702 is also ideal for marine applications due to its resistance to saltwater and other corrosive elements. It is used in valves, pumps, and heat exchangers, where durability and corrosion resistance are crucial for reliable operation in marine environments.
Inconel 702’s unique combination of high strength, excellent corrosion resistance, and high-temperature properties makes it versatile for demanding applications across multiple industries, including aerospace, power generation, chemical processing, and marine environments.
Inconel 702 is highly resistant to oxidation, a crucial property for materials in high-temperature environments. This resistance is primarily due to the alloy’s composition, particularly the presence of chromium and aluminum.
Chromium and aluminum in Inconel 702 react with oxygen to form a stable oxide layer that protects the metal by preventing further oxidation. If the oxide layer is damaged, it can reform itself, continuing to protect the alloy.
Inconel 702 resists oxidation at temperatures up to 2400°F (1316°C), making it ideal for high-heat applications like jet engines, furnace parts, and afterburner liners. The alloy’s ability to maintain its integrity and resist scaling at such high temperatures ensures long-term reliability and durability.
Inconel 702 also exhibits outstanding corrosion resistance, making it suitable for use in highly corrosive environments.
Thanks to its high nickel and chromium content, Inconel 702 resists a variety of corrosive agents such as acids, alkalis, and saltwater. This makes it an ideal choice for applications in chemical processing, marine environments, and oil refineries, where exposure to corrosive substances is common.
Inconel 702 also resists localized corrosion like pitting and crevice corrosion, which are common in chloride environments and can cause quick material failure. The alloy’s resistance to these types of corrosion ensures its longevity and reliability in harsh conditions.
This combined resistance to oxidation and corrosion ensures the longevity and reliability of Inconel 702 in demanding applications. Its ability to withstand both high temperatures and corrosive environments means it can be used in a variety of industries, including aerospace, power generation, and chemical processing. The alloy’s robust performance in these challenging conditions helps reduce maintenance costs and extends the service life of critical components.
In summary, the outstanding oxidation and corrosion resistance of Inconel 702 make it a top choice for industries needing materials that can withstand extreme conditions.
Heat treatment is essential for enhancing the mechanical properties of Inconel 702. This alloy can be subjected to various heat treatment methods to achieve optimal strength, durability, and performance characteristics.
Solution annealing involves heating Inconel 702 to high temperatures between 1080°C and 1120°C (1976°F and 2048°F) and then rapidly cooling it. This treatment dissolves precipitates and homogenizes the microstructure, resulting in a softer and more ductile material, which can be further processed or hardened.
Age hardening, or precipitation hardening, heats the alloy to 650°C-750°C (1202°F-1382°F) for several hours, forming fine precipitates that strengthen the alloy. This process significantly improves the tensile strength and yield strength of Inconel 702, making it suitable for high-stress applications.
Cold working refers to deforming Inconel 702 at room temperature to increase its strength and hardness.
Rolling reduces the alloy’s thickness by passing it between rollers, while drawing pulls it through a die to create wires or rods. Both methods increase dislocation density, enhancing the material’s mechanical properties.
Cold forging shapes the alloy using compressive forces, increasing hardness and strength by refining the grain structure.
Combining heat treatment and cold working techniques allows manufacturers to customize Inconel 702 for specific applications.
Controlling heat treatment and cold working precisely can balance strength and ductility. For example, a higher degree of cold working followed by a moderate age hardening treatment can result in an alloy with excellent tensile strength and good elongation.
Solution annealing can improve corrosion resistance by homogenizing the microstructure and reducing segregated phases that could cause corrosion.
Specific heat treatment cycles can enhance Inconel 702’s performance at high temperatures, often combining solution annealing and age hardening for strength and oxidation resistance.
When heat treating Inconel 702, consider several key factors:
Understanding and applying the right techniques ensures Inconel 702 performs reliably and lasts longer in demanding applications.
Inconel 702, a nickel-based superalloy, poses machining challenges due to its high strength, tendency to work-harden, and toughness. However, its relatively lower hardness compared to other nickel alloys offers some advantages.
Inconel 702 has a machinability rating of about 19%, which is higher than many other nickel-based alloys. This rating indicates its relative ease of machining, though it still requires careful handling and specialized techniques.
Choosing the right cutting speeds is essential for machining Inconel 702 efficiently and extending tool life.
Use carbide inserts with positive rake angles to lower cutting forces and heat. Sharp, positive cutting edges help minimize work hardening and improve surface finish.
While high-speed steel (HSS) tools can be used, carbide tools are preferred for their wear resistance. Employ climb milling to reduce tool pressure and heat.
Use rigid setups and carbide-tipped drills for drilling Inconel 702. Maintaining a consistent feed rate is essential to prevent work hardening and ensure efficient chip removal.
Key challenges include work hardening, heat generation, and tool wear:
Inconel 702 is available in various forms such as bars, pipes, coils, plates, sheets, wires, and fittings.
For best results, use carbide or ceramic tools, high-pressure coolants, consistent feed rates, positive rake angles, and interrupted cutting techniques. By following these guidelines and leveraging the inherent properties of Inconel 702, manufacturers can effectively machine this high-performance alloy, ensuring precision and longevity in demanding applications.
Inconel 702 is a nickel-based superalloy known for its excellent performance at high temperatures. The alloy’s chemical composition is crucial for its high-temperature capabilities, which includes:
These elements work together to provide Inconel 702 with its superior high-temperature properties.
Inconel 702 exhibits a tensile strength of up to 130 ksi (893 MPa) and a yield strength of 95 ksi (655 MPa) at room temperature, retaining much of this strength even at elevated temperatures. This retention of strength is essential for applications subjected to extreme heat, ensuring the material does not deform or fail under stress.
Inconel 702 can resist oxidation up to 2400°F (1316°C), thanks to a protective oxide layer formed by its chromium and aluminum content. This resistance is crucial for maintaining material integrity in high-temperature environments.
Creep resistance allows Inconel 702 to maintain its shape and mechanical properties over long periods under high stress and temperature. This ensures the material remains reliable even under continuous high-temperature exposure.
Inconel 702 offers good thermal conductivity and stable electrical resistivity at high temperatures, ensuring efficient heat dissipation and consistent electrical performance. These properties are essential for applications that require both thermal and electrical reliability.
Inconel 702 is ideal for furnace components due to its high-temperature strength and oxidation resistance, ensuring durability in extreme heat.
Its strength and oxidation resistance make Inconel 702 perfect for jet engine heat exchangers, which endure intense thermal cycling.
In aerospace, Inconel 702 is used for afterburner liners because it resists high temperatures and thermal fatigue.
Inconel 702 is also used in various other high-temperature environments where its unique combination of strength, corrosion resistance, and thermal stability is beneficial. This includes power generation, chemical processing, and marine applications where materials are subjected to extreme conditions.
Inconel 702’s combination of strength, oxidation resistance, and thermal stability makes it a reliable choice for demanding high-temperature applications in various industries.
Below are answers to some frequently asked questions:
Inconel 702, also known as UNS N07702, is a nickel-chromium alloy with the following chemical composition: Nickel (Ni) 79%, Chromium (Cr) 14.00-17.00%, Aluminum (Al) 2.75-3.75%, Iron (Fe) 1.0-2.0%, Titanium (Ti) 0.25-1.00%, Cobalt (Co) up to 1.00%, Manganese (Mn) up to 1.00%, Carbon (C) 0.04-0.10%, Silicon (Si) 0.20-0.70%, Sulfur (S) up to 0.010%, and Copper (Cu) up to 0.50%. These elements contribute to its high-temperature strength, oxidation resistance, and durability.
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Inconel 702 resists oxidation and corrosion due to its specific chemical composition, which includes significant amounts of nickel, chromium, and aluminum. The aluminum in the alloy forms a stable oxide layer on the surface when exposed to high temperatures, protecting it from further oxidation up to 2400°F (1316°C). Chromium also contributes by forming a passive oxide layer that shields the material from corrosive environments. These protective oxide layers, combined with the alloy’s balanced composition, prevent degradation from oxygen and corrosive agents, ensuring high performance in demanding, high-temperature applications.
The recommended machining techniques for Inconel 702 involve using sharp, positive cutting edges with specific geometries designed for superalloys. For turning, it is advisable to use a grade with a very hard substrate and a thin PVD coating. For milling, a grade with a semi-hard substrate and PVD coating is recommended. Cutting speeds for turning should be in the range of 210-280 SFM (65-85 m/min), while milling speeds should be 160-210 SFM (50-65 m/min). Other operations such as parting, grooving, and drilling have specific speed ranges as well. It is crucial to ensure stable tool and workpiece clamping, maintain a short overhang, and use good quality raw material to achieve optimal results. Advanced techniques like modern toolpaths and high-efficiency milling can further enhance productivity and quality.
Heat treatment significantly enhances the properties of Inconel 702, particularly through processes like age hardening. Age hardening increases the alloy’s strength up to temperatures of 1500°F (816°C) by forming precipitates that strengthen the material. Additionally, heat treatment can modify the microstructure, optimizing tensile and yield strength, as well as elongation. While the alloy’s oxidation resistance up to 2400°F (1316°C) is primarily due to its chemical composition, heat treatment allows for the customization of mechanical properties, making Inconel 702 suitable for demanding high-temperature applications.
Inconel 702 is highly beneficial in several industries due to its excellent high-temperature strength, oxidation resistance, and corrosion resistance. The primary industries that benefit the most from using Inconel 702 include:
These industries leverage Inconel 702’s unique properties to enhance the performance and longevity of their equipment and components in challenging conditions.
