AMS 5542 Inconel Alloy X750: Detailed Composition, Properties, Applications, and Heat Treatment
Imagine an alloy that can withstand the relentless heat of a jet engine, the corrosive environment of a nuclear reactor,…
When it comes to high-performance alloys, two names often stand out: Inconel X-750 and Inconel 718. These superalloys, renowned for their exceptional strength and resistance to extreme conditions, are indispensable in industries ranging from aerospace to power generation. But what sets them apart? Whether you’re an engineer deciding on materials for jet engine components or a procurement officer in the oil and gas sector, understanding the differences between these two alloys is crucial.
In this article, we delve into the unique properties of Inconel X-750 and Inconel 718, comparing their chemical compositions, mechanical strengths, and resistance to temperature and corrosion. We’ll explore their specific applications, shedding light on why one might be preferred over the other in certain scenarios. By the end, you’ll have a clear picture of how these alloys perform in various environments and which one is best suited for your particular needs. So, let’s embark on this metallurgical journey and uncover what makes Inconel X-750 and Inconel 718 both similar and distinct.
Inconel X-750 is a nickel-chromium alloy known for its high strength and excellent resistance to corrosion and oxidation. Its composition primarily includes nickel, chromium, and titanium:
Tensile Strength:
Inconel X-750 has a tensile strength ranging from 900 to 1750 N/mm² (130-254 ksi), depending on heat treatment and condition.
Creep Rupture Strength:
This alloy maintains its structural integrity at high temperatures up to about 700°C (1290°F), making it ideal for prolonged high-stress applications.
Impact Strength:
Inconel X-750 has good impact strength, even at cryogenic temperatures, ensuring durability under sudden shocks and extreme conditions.
Density:
The density of Inconel X-750 is 8.28 g/cm³ (0.299 lbs/in³), contributing to its strength and durability.
Modulus of Elasticity:
With a modulus of elasticity of 214 GPa (31.0 Mpsi), Inconel X-750 is highly stiff, suitable for applications requiring minimal deformation.
Thermal Conductivity:
Its thermal conductivity is 12.0 W/(m°C) (83 BTUin/(hrft²°F)), allowing effective heat conduction in high-temperature environments.
Coefficient of Thermal Expansion:
The coefficient of thermal expansion is 12.6 µm/m°C (7.0 µin/(in°F)), ensuring predictable expansion and contraction with temperature changes.
Inconel X-750 can be strengthened through heat treatments like aging, annealing, and stabilizing, which enhance its strength, workability, and resistance to stress corrosion.
Inconel X-750 resists oxidation and corrosion even at high temperatures, thanks to its chromium content, which forms a protective oxide layer.
Inconel X-750 is used in aerospace, nuclear reactors, gas turbines, and automotive industries for components exposed to high stress and temperatures.
Inconel 718 is a nickel-chromium alloy designed to offer exceptional mechanical properties and corrosion resistance due to its well-balanced composition. The primary elements in Inconel 718 include:
Inconel 718 exhibits impressive mechanical properties, making it suitable for high-stress applications. The ultimate tensile strength is approximately 135,000 psi (1370 MPa), and the yield strength is around 70,000 psi (1030 MPa).
Inconel 718 can stretch 12-15% before breaking, which means it has good ductility. In its aged condition, it has a hardness of Rockwell B 100 or HRC 45, making it resistant to deformation and wear.
Inconel 718 maintains its mechanical properties up to 700°C, making it ideal for moderate to high-temperature applications.
Inconel 718 is highly resistant to various forms of corrosion, including:
With a density of approximately 8.19 g/cm³ (0.296 lbs/in³) and a modulus of elasticity of around 211 GPa (30.6 Mpsi), Inconel 718 exhibits high stiffness, making it suitable for applications requiring minimal deformation under load.
Inconel 718 has a low thermal conductivity of about 11.4 W/(m·°C), which helps reduce thermal stress at high temperatures. Its coefficient of thermal expansion is about 13.0 µm/m·°C, ensuring predictable expansion and contraction with temperature changes.
Inconel 718 is easy to weld and resists post-weld age cracking, making it ideal for precision fabrications in aerospace and other critical applications.
Inconel 718’s balanced composition and mechanical properties make it versatile for demanding applications. Its high strength, good ductility, excellent corrosion resistance, high-temperature performance, and weldability make it a top choice for industries like aerospace, chemical processing, and power generation.
Inconel X-750 is widely used in the aerospace industry due to its remarkable high-temperature strength and corrosion resistance. Its ability to endure high temperatures and stresses makes it perfect for turbine blades and vanes in jet engines and gas turbines. The alloy is also employed in thrust reversers and rocket engine parts, providing durability and reliability under extreme conditions. Inconel X-750 is ideal for springs and fasteners, maintaining strength from sub-zero temperatures up to 1200°F (649°C).
The nuclear and power generation industries rely on Inconel X-750 for its high-temperature stability and corrosion resistance. Its stability and strength under radiation and high temperatures make it suitable for reactor core components. Inconel X-750 is used in steam generators and heat exchangers for its corrosion resistance and durability at high temperatures.
The oil and gas industry values Inconel X-750 for its strength and resistance to corrosive environments. Its durability and resistance to stress corrosion cracking make it ideal for harsh drilling conditions. Inconel X-750’s high strength and resistance to hydrogen embrittlement ensure reliable performance in extreme downhole environments.
In the automotive industry, Inconel X-750 is used where high strength and resistance to oxidation and corrosion are essential. The alloy is perfect for exhaust systems and turbocharger components, withstanding high temperatures and corrosive gases.
Inconel X-750’s high-temperature properties make it ideal for heat-treating applications. Its strength and high-temperature resistance are perfect for forming tools and extrusion dies. Inconel X-750 withstands high temperatures and mechanical stress, making it ideal for test machine grips.
Inconel X-750’s unique combination of strength and corrosion resistance makes it suitable for large pressure vessels, ensuring reliable performance under high pressure and temperature conditions.
In the aerospace industry, Inconel 718 is invaluable due to its ability to withstand high temperatures and stress. This alloy is commonly used in gas turbine components, such as turbine blades, compressor wheels, and engine exhaust systems, where it provides durability and high performance under extreme conditions. Additionally, Inconel 718 is utilized in jet engines, rocket motors, and thrust reversers, offering reliable performance in demanding aerospace applications.
Inconel 718 plays a vital role in power generation, offering exceptional high-temperature strength and oxidation resistance. These properties are crucial for the efficiency and reliability of gas turbines. The alloy is also used in steam turbines and other critical components of power plants, contributing to the durability and longevity of these systems.
In the oil and gas industry, Inconel 718 is highly valued for its excellent corrosion resistance and high strength. This alloy is ideal for downhole shafting, high-strength bolting, and other components exposed to harsh drilling environments. Its resistance to hydrogen embrittlement (weakening of metal due to hydrogen) and stress corrosion cracking makes it suitable for use in extreme conditions, ensuring the reliability and safety of drilling and extraction operations.
Moving on to the chemical processing industry, Inconel 718’s resistance to various forms of corrosion, including chloride and sulfide stress corrosion cracking, makes it suitable for a range of applications. The alloy is used in components such as reactor vessels, heat exchangers, and piping systems, providing long-term durability and performance in corrosive environments. Its ability to withstand a wide range of temperatures further enhances its suitability for chemical processing.
In marine environments, where seawater exposure is a concern, Inconel 718 is highly valued for its superior corrosion resistance. The alloy is employed in components such as propeller shafts, seawater pump shafts, and various marine hardware, offering long-lasting performance and resistance to corrosion in saltwater environments.
Inconel 718 is also used in cryogenic storage tanks. It maintains excellent strength over a wide temperature range, from -423°F to 1300°F. This makes the alloy suitable for applications requiring durability and stability at extremely low temperatures, ensuring the safe storage and handling of cryogenic materials.
In the nuclear industry, Inconel 718 is used for nuclear fuel element spacers and other critical components. Its high strength, corrosion resistance, and ability to withstand radiation and high temperatures make it an essential material for ensuring the safety and efficiency of nuclear reactors.
The chemical composition of Inconel X-750 and Inconel 718 is a critical factor that distinguishes these two alloys. Inconel 718 contains 50-55% Nickel, 17-21% Chromium, 2.8-3.3% Molybdenum, and 4.75-5.5% Niobium, with Iron as the balance. In contrast, Inconel X-750 has at least 70% Nickel, 14-17% Chromium, and 2.25-2.75% Titanium, with Iron comprising 5-9%.
Inconel 718 boasts a tensile strength of 1370 MPa and a yield strength of 1030 MPa, with an elongation of 12-15% and a hardness rating between B95 and C36. In comparison, Inconel X-750 offers a tensile strength of 1100 MPa, a yield strength of 780 MPa, an elongation of 15-20%, and a hardness rating between B88 and C32.
Inconel 718 is suitable for applications up to 700°C, maintaining its properties well. However, Inconel X-750 can withstand higher temperatures, up to 980°C, making it ideal for applications requiring high-temperature resistance.
Inconel 718 provides superior corrosion resistance, especially against general and pitting corrosion, thanks to its molybdenum and higher chromium content. Inconel X-750 also resists general and pitting corrosion well but has moderate resistance to stress corrosion cracking.
Inconel 718 is perfect for high-strength, corrosive environments such as oil and gas and aerospace applications. In contrast, Inconel X-750 excels in extremely high-temperature settings, like turbines and nuclear reactors.
Inconel 718 is generally more expensive but easier to machine. Inconel X-750 is more affordable but harder to machine due to its toughness.
Inconel 718 offers excellent weldability, making it suitable for precision fabrications, whereas Inconel X-750 is less weldable but manageable with proper techniques.
Below are answers to some frequently asked questions:
Inconel X-750 and Inconel 718 are both nickel-chromium alloys but differ significantly in their chemical composition, mechanical properties, and application suitability. Inconel X-750 contains significant amounts of aluminum and titanium, which make it precipitation hardenable, while Inconel 718 includes niobium and molybdenum, enhancing its strength and corrosion resistance. Mechanically, Inconel X-750 is known for its high strength and excellent creep-rupture properties at elevated temperatures, making it ideal for high-temperature and cryogenic applications. In contrast, Inconel 718 offers exceptionally high yield, tensile, and creep-rupture strengths, along with superior oxidation and corrosion resistance, especially in chloride and sulfide environments. Inconel 718 is also preferred for its excellent welding characteristics and resistance to post-weld age cracking. Overall, Inconel 718 is typically chosen for applications requiring high strength across a broad temperature range, while Inconel X-750 is valued for its performance in both high and cryogenic temperatures.
Inconel X-750 is primarily used in aerospace for rocket-engine thrust chambers, airframe components, and hot-air ducting systems. It is also employed in springs and fasteners, heat-treating fixtures, large pressure vessels, and various components in the oil & gas, nuclear, power generation, and automotive industries due to its high strength and resistance to corrosion and high temperatures.
Inconel 718, on the other hand, finds extensive use in aerospace for gas turbine components, jet engines, pump bodies, rocket motors, and thrust reversers. It is also used in cryogenic storage tanks, power generation equipment, and various oil & gas industry components. Additionally, Inconel 718 is suitable for marine projects, chemical and petrochemical plants, and nuclear reactors, thanks to its excellent oxidation resistance and high-temperature strength.
While both alloys are used in high-temperature and corrosive environments, Inconel 718’s superior oxidation resistance and versatility make it more suitable for a broader range of industries, including marine and petrochemical applications.
Inconel X-750 and Inconel 718 both exhibit excellent mechanical properties, but they differ in several key areas. Inconel 718 generally has higher tensile strength and yield strength compared to Inconel X-750. In the annealed and aged condition, Inconel 718’s tensile strength is typically over 860 MPa (125 ksi), while Inconel X-750’s tensile strength ranges from 1100-1750 N/mm² (160-254 ksi) depending on the heat treatment. Yield strength for Inconel 718 ranges from 965-1034 MPa (140-150 ksi), while for Inconel X-750, it varies widely based on treatment, reaching up to 1350-1750 N/mm² (196-254 ksi) in the Spring Temper + Aged condition.
In terms of high-temperature performance, both alloys perform well, but Inconel X-750 is noted for good creep-rupture strength up to about 700°C (1290°F), while Inconel 718 maintains excellent mechanical properties up to around 650°C (1200°F). Inconel 718 also has superior fatigue resistance and better overall corrosion resistance, particularly against chloride and sulfide stress corrosion cracking.
In summary, Inconel 718 is generally preferred for its higher strength, better fatigue resistance, and superior corrosion resistance, while Inconel X-750 is valued for its creep-rupture strength at high temperatures and wide operating temperature range. The choice between the two depends on the specific requirements of the application.
For high-temperature applications, Inconel X-750 is generally the better choice. It offers superior oxidation resistance and maintains significant strength at temperatures up to 1800°F (982°C). Additionally, its excellent creep resistance and thermal stability make it ideal for components operating in extremely hot and corrosive environments. While Inconel 718 also performs well at elevated temperatures, it does not match the oxidation resistance and high-temperature stability of Inconel X-750.
Inconel X-750 and Inconel 718 are commonly used in the aerospace, automotive, marine, oil and gas, and chemical processing industries. In the aerospace industry, both alloys are utilized for components in jet engines, gas turbines, and rocket motors due to their high-temperature strength and reliability. The automotive industry employs these alloys in high-performance engine parts like turbochargers and exhaust systems. In the marine industry, they are used for components exposed to seawater and high pressures, such as propeller shafts and downhole tools. The oil and gas industry uses these alloys in downhole equipment and refining systems due to their resistance to harsh environments. Additionally, the chemical processing industry benefits from their use in reactors, heat exchangers, and other high-temperature components.
