UNS N08800 - Ensuring High-Temperature Corrosion Resistance


In various industries, high-temperature environments leave materials vulnerable to corrosion. To combat this challenge, the UNS N08800 Hex Head Bolt has emerged as a robust solution. This article delves into the significance of this product, highlighting its best-in-class corrosion resistance properties and exploring its applications in different industries. 

Understanding UNS N08800

1.1 Overview of UNS N08800
UNS N08800, also known as Alloy 800 or Incoloy 800, is an austenitic nickel-iron-chromium alloy. It falls under the category of high-temperature alloys, specifically designed to withstand corrosive environments at elevated temperatures. With its excellent corrosion resistance and mechanical properties, UNS N08800 is widely used in various industrial applications.

1.2 Chemical Composition and Physical Properties
UNS N08800 has a chemical composition of approximately 32% nickel, 21% chromium, 46% iron, and trace amounts of other elements such as copper, aluminum, and titanium. This unique composition provides the alloy with its superior resistance to corrosion and oxidation, even in highly aggressive conditions.

The physical properties of UNS N08800 include a density of 7.94 g/cm3, a melting point of 1385-1420°C, and a thermal conductivity of 11.5 W/m·K. Its tensile strength is typically around 500 MPa, with a yield strength of approximately 210 MPa.

1.3 Key Features of UNS N08800
UNS N08800 offers several key features that make it suitable for high-temperature applications:

1.3.1 High-Temperature Strength: At elevated temperatures, UNS N08800 exhibits excellent mechanical strength, allowing it to withstand the stresses and strains of demanding conditions.

1.3.2 Corrosion Resistance: The alloy demonstrates remarkable resistance to oxidation and corrosion in a wide range of environments, including sulfuric acid, nitric acid, and chloride-containing solutions.

1.3.3 Thermal Stability: UNS N08800 can maintain its mechanical properties and dimensional stability, even in extreme temperature fluctuations.

1.3.4 Stability against Hydrogen Embrittlement: The alloy is resistant to hydrogen embrittlement, ensuring its integrity and reliability in hydrogen-rich environments.

1.4 Corrosion Resistance Mechanisms
UNS N08800 owes its corrosion resistance to a combination of mechanisms, including:

1.4.1 Chromium Oxide Passivation: The high chromium content in the alloy forms a protective oxide layer on the surface, preventing further corrosion and oxidation.

1.4.2 Nickel-Iron Matrix: The nickel-iron matrix provides additional corrosion resistance, especially against sulfuric acid and other acidic environments.

1.4.3 Carburization Resistance: The alloy resists carburization, a process in which carbon diffuses into the material, causing structural degradation.

1.5 Comparison with other Heat Resistant Alloys
Compared to other heat-resistant alloys, such as Inconel 600 and Inconel 601, UNS N08800 offers distinct advantages. While sharing similar corrosion resistance properties, UNS N08800 exhibits superior strength and resistance to oxidation at high temperatures. Additionally, it has better creep and rupture properties, making it highly reliable for long-term use in extreme environments.


Applications and Examples

2.1 Petrochemical Industry
The petrochemical industry extensively utilizes UNS N08800 Hex Head Bolts fastener in various applications due to their exceptional heat and corrosion resistance.

2.1.1 Furnaces and Heaters
In furnaces and heaters, where extreme temperatures and corrosive gasses or liquids are present, UNS N08800 Hex Head Bolts are essential for securing critical components and maintaining structural integrity. These components include radiant tubes, tubesheets, and gas burners.

2.1.2 Heat Exchangers and Condensers
Heat exchangers and condensers are vital for efficient heat transfer in petrochemical plants. UNS N08800 Hex Head Bolts are used to assemble and secure the plates, tubes, and other components of these heat exchange systems. The alloy's corrosion resistance ensures prolonged service life and reliable performance.

2.1.3 Catalyst Regenerators
Catalyst regenerators in petrochemical processes often encounter highly corrosive and high-temperature conditions. UNS N08800 Hex Head Bolts are used in these applications to ensure the integrity of the regenerator vessel and associated internal components, such as baffles, cone chambers, and flanges.

2.2 Power Generation Industry
The power generation industry relies on high-temperature corrosion-resistant materials like UNS N08800 Hex Head Bolts to maintain efficient and reliable power production.

2.2.1 Steam Turbines and Boiler Systems
Steam turbines and boiler systems operate under high temperatures and pressures that can lead to corrosion and stress-related failures. UNS N08800 Hex Head Bolts are utilized in critical areas such as turbine blades, valve assemblies, and boiler tubes, guaranteeing the integrity and safety of these high-pressure systems.

2.2.2 Gas Turbines
Gas turbines are widely used in power generation, requiring durable materials to withstand the high-temperature combustion environment. UNS N08800 Hex Head Bolts are employed in the turbine sections, exhaust systems, and combustion liners, ensuring resistance to oxidation and corrosion in these demanding conditions.

2.2.3 Nuclear Power Plants
In nuclear power plants, where safety and reliability are paramount, UNS N08800 Hex Head Bolts are used for various applications, including securing reactor vessel components, steam generators, and control rod drive mechanisms. The exceptional corrosion resistance and thermal stability of this alloy make it a preferred choice for nuclear power applications.

2.3 Aerospace Industry
In the aerospace industry, where weight, strength, and high-temperature resistance are crucial, UNS N08800 Hex Head Bolts find extensive use in critical aerospace applications.

2.3.1 Jet Engines
Jet engines operate under extreme conditions, including high temperatures and corrosive combustion gases. UNS N08800 Hex Head Bolts are employed in engine components such as turbine blades, combustion chambers, and afterburners, ensuring the stability and longevity of these vital aerospace systems.

2.3.2 Exhaust Systems
Exhaust systems in aircraft require materials that can withstand the high-temperature environment and resist corrosion from exhaust gases. UNS N08800 Hex Head Bolts are used to secure the components of exhaust systems, including the turbocharger, manifold, and catalytic converter, ensuring safe and efficient operation.

2.3.3 Aerospace Fasteners
The aerospace industry relies on high-performance fasteners to ensure structural integrity and safety. UNS N08800 Hex Head Bolts are used in critical aerospace applications to securely fasten components together, including aircraft frames, landing gear assemblies, and wing structures.

2.4 Oil and Gas Industry
The oil and gas industry operates in harsh conditions, including offshore environments and high-pressure, high-temperature applications. UNS N08800 Hex Head Bolts provide reliable corrosion resistance in these demanding situations.

2.4.1 Offshore Drilling Platforms
Offshore drilling platforms are exposed to corrosive seawater and fluctuating temperatures. UNS N08800 Hex Head Bolts are used in the construction of these platforms to secure structural components, ensuring resistance to both marine corrosion and high-temperature conditions.

2.4.2 Subsea Equipment
Subsea equipment, such as oil wellhead assemblies and pipelines, require material that can withstand high pressures, aggressive fluids, and seawater corrosion. UNS N08800 Hex Head Bolts are utilized in these applications, ensuring the integrity and longevity of subsea assets.

2.4.3 Oil Refineries
In oil refineries, where various corrosive chemicals and high temperatures exist, UNS N08800 Hex Head Bolts are used to secure process equipment, piping, and vessels. The alloy's resistance to sulfuric acid, hydrochloric acid, and other aggressive media ensures reliable performance and reduced maintenance requirements.

Overall, UNS N08800 Hex Head Bolts find extensive applications in diverse industries due to their high-temperature corrosion resistance and mechanical strength. From the petrochemical industry to power generation, aerospace, and oil and gas sectors, these bolts provide the reliability and durability required in demanding environments.

Benefits and Advantages

3.1 Enhanced High-Temperature Corrosion Resistance
One of the primary benefits of UNS N08800 is its exceptional corrosion resistance at high temperatures. It can withstand harsh environments, including acids, alkaline solutions, and gases, without significant degradation. This makes it ideal for applications in industries such as petrochemicals, power generation, aerospace, and oil and gas, where elevated temperatures and corrosive substances are prevalent.

3.2 Longevity and Durability
UNS N08800 offers excellent mechanical properties, including high tensile and yield strength, even at elevated temperatures. This ensures the longevity and durability of components made from this alloy. Its resistance to deformation and creep allows it to maintain its structural integrity over an extended period, reducing the need for frequent replacements and maintenance.

3.3 Minimal Maintenance Required
Due to its corrosion resistance and high-temperature strength, components made from UNS N08800 require minimal maintenance. They can withstand harsh operating conditions without significant deterioration, resulting in reduced downtime and maintenance costs. This advantage is particularly significant for industries such as oil and gas and power generation, where maintenance and repair operations can be costly and time-consuming.

3.4 Cost-Effectiveness
Although the initial cost of UNS N08800 may be higher than that of conventional materials, its long-term cost-effectiveness becomes apparent due to its extended service life and reduced maintenance requirements. The durability and reliability of the alloy minimize the need for frequent replacements and repairs, resulting in cost savings over the lifespan of the equipment or structure.

3.5 Compliance with International Standards
UNS N08800 complies with various international standards and specifications, ensuring its quality and reliability. It meets the requirements set forth by organizations such as ASTM International, which standardizes materials and testing procedures, and ASME (American Society of Mechanical Engineers) for pressure vessel applications. This compliance provides further assurance of its suitability for critical applications in different industries.


Case Studies

4.1 Case 1: Petrochemical Industry Application
In a large petrochemical plant, the reformer furnace tubes are constantly exposed to high temperatures and corrosive gases. Using UNS N08800 tubes in this application has proven highly effective in preventing corrosion and maintaining tube integrity. These tubes, which form the backbone of the furnace, have been able to withstand the harsh conditions, resulting in improved operational performance and extended service life. The minimal maintenance required has also resulted in cost savings for the plant.

4.2 Case 2: Power Generation Industry Application
In a steam turbine power plant, UNS N08800 Hex Head Bolts are utilized to secure the blade assemblies in the turbine. The bolts provide excellent resistance to corrosion and high temperatures, ensuring the integrity and safety of the turbine. The longevity and durability of UNS N08800 bolts have significantly reduced the need for maintenance and replacement, leading to improved turbine efficiency and reduced downtime for the power plant.

4.3 Case 3: Aerospace Industry Application
In the aerospace industry, jet engines operate in extreme conditions that require materials with high-temperature resistance and corrosion resistance. By using UNS N08800 in the construction of critical components such as turbine blades and combustion chambers, jet engines have achieved improved performance, extended service life, and increased reliability. The exceptional mechanical properties of UNS N08800 have contributed to enhanced engine efficiency and reduced maintenance requirements.

4.4 Case 4: Oil and Gas Industry Application
In an offshore oil drilling platform, subsea pipelines are subjected to aggressive seawater corrosion and high-pressure conditions. By utilizing UNS N08800 Hex Head Bolts in the construction of these pipelines, the platform has experienced improved corrosion resistance and increased longevity. The minimal maintenance required has resulted in significant cost savings for the operator, as offshore maintenance operations are typically expensive and time-consuming.

These case studies highlight the benefits and advantages of UNS N08800 in different industry applications. From improved operational performance and extended service life to reduced maintenance and cost savings, the use of UNS N08800 has demonstrated its worth in demanding environments.



The UNS N08800 Hex Head Bolt has emerged as a game-changer in the fight against high-temperature corrosion. Its exceptional resistance to corrosive environments has made it a preferred choice in industries such as petrochemical, power generation, aerospace, and oil and gas. With its excellent properties, including longevity, durability, low maintenance requirements, and compliance with international standards, the UNS N08800 Hex Head Bolt offers a reliable and cost-effective solution for various applications. As industries continue to push the limits of heat and pressure, this high-temperature corrosion-resistant bolt is poised to play a vital role in supporting the longevity and efficiency of critical infrastructure.

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