Incoloy 800H (UNS N08810): Uses, Properties, and Composition
When it comes to materials that can withstand extreme temperatures and corrosive environments, Incoloy 800H stands out as a premier…
When it comes to high-temperature applications, choosing the right alloy can make all the difference. Incoloy 800H and 800HT are two such alloys that often come under scrutiny for their remarkable performance in extreme conditions. While they may appear similar at first glance, the nuanced differences in their chemical compositions, mechanical properties, and optimal working temperatures can significantly impact their suitability for various industrial applications. Whether you’re an engineer selecting materials for a high-stress environment, a procurement specialist seeking the best fit for your project, or a technician ensuring proper maintenance, understanding these differences is crucial. Dive in as we unravel the unique attributes of Incoloy 800H and 800HT, helping you make informed decisions that meet your specific needs.
Incoloy alloys are a group of superalloys made primarily of nickel, iron, and chromium. These materials are engineered to perform well under extreme conditions, particularly high temperatures and corrosive environments.
The key advantage of Incoloy alloys is their outstanding resistance to oxidation, carburization, and other high-temperature corrosion forms. This makes them essential in industries like power generation, chemical processing, and aerospace, where materials face harsh conditions.
The 800 series, including Incoloy 800, 800H, and 800HT, is notable for high-temperature applications. Incoloy 800 is the base alloy, while 800H and 800HT are enhanced versions designed for better performance under different conditions.
The main differences between Incoloy 800H and 800HT lie in their chemical compositions and mechanical properties. These differences are tailored to provide better performance in specific temperature ranges and stress conditions.
Incoloy 800H and 800HT are commonly used in applications that require materials to maintain strength and resist degradation at high temperatures, such as heat exchangers, gas turbines, and petrochemical industry components. The choice between 800H and 800HT depends on the specific temperature and mechanical requirements of the application.
Both Incoloy 800H and 800HT can be dual-certified, meaning they meet the specifications for both alloys. This provides flexibility in material selection, ensuring reliable performance under varying conditions. Dual certification is particularly beneficial in industries with a wide range of operating temperatures.
For engineers, designers, and material specialists, understanding the differences between Incoloy 800H and 800HT is crucial for selecting the right material for high-temperature applications. This overview prepares us for a deeper dive into their chemical compositions, working temperatures, mechanical properties, and specific uses.
Incoloy 800H and 800HT are nickel-iron-chromium alloys with similar basic compositions. These alloys include the following elements:
The main difference in carbon content is that Incoloy 800H has 0.05-0.10% carbon, while Incoloy 800HT has 0.06-0.10% carbon. This slight variation influences the mechanical properties of the alloys, particularly their creep and rupture strength at high temperatures.
The alloys also differ in their aluminum and titanium content. Incoloy 800H has 0.15-0.60% aluminum and titanium each, with a combined total of 0.30-1.20%. Incoloy 800HT has 0.25-0.60% aluminum and titanium each, with a combined total of 0.85-1.20%.
Both alloys undergo high-temperature annealing to achieve an average grain size of ASTM 5 or coarser, enhancing their creep and rupture strength at elevated temperatures. This treatment, combined with their controlled levels of carbon, aluminum, and titanium, is crucial in improving their high-temperature properties.
Incoloy 800HT’s composition falls within the limits of Incoloy 800H, but not vice versa, making 800HT suitable for applications requiring stricter material properties.
Incoloy 800H is designed to perform effectively in high-temperature environments. The typical working temperature range for Incoloy 800H is from 1100°F (593°C) to 1290°F (700°C). Its good creep-rupture strength makes it ideal for applications needing consistent performance over extended periods at high temperatures.
Incoloy 800HT is optimized for even higher temperature applications than Incoloy 800H. Its improved chemical makeup with more aluminum and titanium, along with specific heat treatments, contribute to its superior high-temperature strength and stability. This makes it ideal for environments that demand excellent resistance to creep and stress-rupture at temperatures above 1290°F (700°C).
Incoloy 800H is ideal for high-temperature applications up to 1290°F (700°C). Typical uses include:
These applications benefit from its ability to endure long-term high temperatures while retaining mechanical properties and resisting oxidation and carburization.
Incoloy 800HT is preferred for applications needing material stability and strength at temperatures up to 1800°F (982°C). Common applications include:
Its superior high-temperature strength and creep resistance make it perfect for these demanding conditions.
Choosing between Incoloy 800H and 800HT depends primarily on the required operational temperature. Incoloy 800H is suitable for up to 1290°F (700°C), while Incoloy 800HT is designed for higher temperatures, offering better performance up to 1800°F (982°C). Understanding these temperature limits ensures the selection of the appropriate alloy to meet the specific requirements of high-temperature applications.
Incoloy 800H and 800HT are renowned for their distinct mechanical properties, which stem from their unique compositions and heat treatments.
Incoloy 800H stands out for its impressive tensile strength, typically around 450 MPa (65,000 psi) in the annealed state. Its yield strength is approximately 170 MPa (25,000 psi), making it a robust choice for various applications.
Incoloy 800HT exhibits a tensile strength ranging from 372 to 531 MPa (54,000 to 77,000 psi) in the annealed state, slightly surpassing that of 800H. Its yield strength varies between 90 to 145 MPa (13,000 to 21,000 psi), providing an edge in specific high-stress environments.
Elongation and hardness are critical indicators of a material’s ductility and resistance to deformation.
Incoloy 800H typically achieves an elongation of around 30% in the annealed state. Its hardness is tailored through specific grain size and thermal treatments to meet diverse application requirements.
Incoloy 800HT’s elongation ranges from 18% to 23% in the annealed state. Its hardness benefits from a controlled grain size, typically ASTM No. 5 or coarser, enhancing its high-temperature properties and machining results.
Creep and rupture strength are vital for materials subjected to high-temperature environments over prolonged periods.
Incoloy 800H has significant resistance to deformation and breaking under prolonged stress at high temperatures, making it suitable for long-term applications. However, its performance is slightly lower compared to 800HT.
Incoloy 800HT excels with its superior resistance to deformation and breaking under prolonged stress. It maintains creep rates of less than 1% per minute at 482°C (900°F) and withstands temperatures up to 574°C (1065°F). The Larson-Miller parameter plot confirms that 800HT outperforms 800H, making it a top choice for high-temperature applications.
High-temperature performance is a critical factor for these alloys, determining their suitability for demanding environments.
Incoloy 800H is suitable for applications up to about 593°C (1100°F). While it can be used at higher temperatures, its performance may diminish.
Incoloy 800HT is recommended for temperatures above 593°C (1100°F) due to its enhanced creep resistance and high-temperature strength. It maintains excellent strength up to about 750°C (1382°F), making it ideal for applications requiring resistance to corrosion and oxidation at elevated temperatures.
Both Incoloy 800H and 800HT are exceptional materials, each with its strengths. Incoloy 800H offers robust mechanical properties suitable for a variety of applications, while Incoloy 800HT provides superior performance in high-temperature and high-stress environments, making it the preferred choice for demanding industrial applications.
Incoloy 800H is widely used in high-temperature environments due to its excellent resistance to oxidation and carburization, making it ideal for various industrial applications.
Incoloy 800H is utilized in ethylene furnace quench boilers, where it must withstand high temperatures and corrosive conditions. Its resistance to oxidation and carburization ensures durability and consistent performance in such demanding conditions.
Hydrocarbon cracking involves high temperatures and corrosive environments. Incoloy 800H is ideal for this application because it remains strong and stable under these conditions, ensuring safe and efficient operations.
Incoloy 800H is used in manufacturing valves, fittings, and other components exposed to high temperatures and corrosive attacks, thanks to its resistance to oxidation and carburization up to 1800°F.
Industrial furnaces need materials that can endure prolonged high temperatures. Incoloy 800H’s high-temperature strength and resistance to oxidation make it a preferred material for structural components in these furnaces.
Incoloy 800H is employed in heat-treating equipment such as baskets, trays, and fixtures. Its high-temperature stability ensures these tools remain reliable and durable during heat treatment.
In chemical and petrochemical processing, Incoloy 800H is used for heat exchangers and piping. Its resistance to chloride stress-corrosion cracking in nitric acid media makes it ideal for these corrosive conditions.
Incoloy 800HT is designed for enhanced high-temperature strength and stability, making it ideal for more extreme conditions than Incoloy 800H.
Incoloy 800HT is ideal for cyclic heating and cooling applications due to its enhanced resistance to grain boundary precipitates. This makes it suitable for environments where temperature fluctuations are frequent.
The additional aluminum and titanium in Incoloy 800HT enhance its performance in industrial furnaces and heat-treating equipment, making it particularly useful for long-term high-temperature exposure.
In power plants, Incoloy 800HT is used for super-heater and re-heater tubing. Its superior high-temperature properties, including enhanced creep strength, make it perfect for these critical components in extreme conditions.
Incoloy 800HT’s improved creep strength and resistance to carburization make it suitable for pressure vessels and heat exchangers in high-temperature, corrosive environments, ensuring reliable and safe operations.
Incoloy 800HT offers higher creep strength than Incoloy 800H, making it more suitable for long-term high-temperature applications. This is particularly important in environments where materials are subjected to prolonged stress at elevated temperatures.
The stabilization of Incoloy 800HT reduces the risk of grain boundary precipitate formation, which is critical in cyclic heating and cooling scenarios. This makes it a better choice for applications involving frequent temperature fluctuations.
Although both alloys withstand high temperatures, Incoloy 800HT is preferred for applications above 1100°F. Its enhanced properties ensure better performance and longevity in extreme high-temperature conditions.
By understanding the distinct advantages of Incoloy 800H and 800HT, engineers and material specialists can choose the best alloy for their high-temperature needs, ensuring optimal performance and durability.
Dual certification means a material meets the standards of two different alloys. For Incoloy 800H and 800HT, this means the alloy satisfies both UNS N08810 and UNS N08811 standards.
Both Incoloy 800H and 800HT are made of nickel, iron, and chromium. The main difference is the aluminum and titanium content, which is more controlled in 800HT.
Both alloys resist oxidation, sulfidation, and carburization, making them ideal for high-temperature environments. Dual certification ensures these strengths are combined.
These alloys are used in furnaces, heat exchangers, and reactors because they perform well under various temperatures.
Their resistance to high-temperature corrosion makes them perfect for reformer tubing, superheater and reheater tubing, and heat treatment equipment.
When choosing dual-certified alloys, consider the specific needs of your application. Understanding the environmental conditions and stress factors will ensure the best material performance.
Below are answers to some frequently asked questions:
The main differences in the chemical composition between Incoloy 800H and 800HT are centered around the levels of carbon, aluminum, and titanium. Incoloy 800H has a carbon content ranging from 0.05% to 0.10%, while Incoloy 800HT has a slightly more restricted carbon content of 0.06% to 0.10%. Additionally, the combined aluminum and titanium content in Incoloy 800H ranges from 0.30% to 1.20%, whereas in Incoloy 800HT, it is more narrowly defined, ranging from 0.85% to 1.20%. These controlled levels in Incoloy 800HT are intended to optimize high-temperature properties, particularly creep and rupture strength. Both alloys share similar base compositions, including 30-35% Nickel (Ni), 19-23% Chromium (Cr), and a minimum of 39.5% Iron (Fe).
The recommended working temperature for Incoloy 800H is up to 1290°F (700°C), making it suitable for applications that involve frequent temperature excursions below this threshold. In contrast, Incoloy 800HT is recommended for continuous service at temperatures above 1290°F (700°C) due to its enhanced high-temperature strength and creep resistance.
The mechanical properties of Incoloy 800H and 800HT are similar in many respects, but there are notable differences due to variations in their chemical compositions and heat treatments. Incoloy 800HT, with its higher aluminum and titanium content, exhibits enhanced creep and stress rupture properties, making it more suitable for high-temperature applications where stability and resistance to creep are critical. While both alloys have comparable tensile and yield strengths at room temperature, 800HT retains its strength better at higher temperatures, maintaining superior mechanical integrity in more extreme environments.
Incoloy 800H and 800HT are commonly used in chemical and petrochemical processing, power generation, thermal processing fixtures, and industrial furnaces. They are utilized in applications such as heat exchangers, steam super-heaters, radiant tubes, muffles, retorts, ethylene pyrolysis, hydrocarbon cracking, pressure vessels, and components in the paper pulp industry and nuclear power plants. These alloys are chosen for their high-temperature resistance and ability to withstand corrosive environments, making them suitable for critical applications in these industries.
Dual certification for Incoloy 800H and 800HT means that the material meets the specifications and requirements for both grades. This certification indicates that the alloy combines the properties of Incoloy 800H, which includes higher carbon content for enhanced creep and rupture strength, with the additional aluminum and titanium in Incoloy 800HT that further improve its high-temperature properties. Essentially, dual certification ensures that the material can be used in applications requiring the optimal performance characteristics of both 800H and 800HT, offering versatility and reliability for high-temperature environments.
Yes, there are overlapping properties between Incoloy 800H and 800HT. Both alloys share a similar chemical composition, excellent high-temperature resistance, superior creep and rupture properties, high tensile strength, good weldability, and excellent general corrosion resistance. These common attributes make them suitable for high-stress environments and applications such as furnace components, heat exchangers, and petrochemical processing equipment. Despite these similarities, they differ in their specific suitability for certain temperature ranges due to variations in their chemical composition and heat treatment processes.
