Incoloy 800 is a titanium-stabilised nickel-based austenitic Ni-Fe-Cr alloy with copper and molybdenum additions. It has excellent resistance to stress corrosion cracking performance and resistance to pitting corrosion and, crevice corrosion performance; excellent oxidation resistance and non-oxidising hot acid performance; at room temperature and up to 550 ° C it has excellent mechanical properties, so it is often used in the manufacture of chemical plants with the heating pipe, heat exchanger, evaporator, etc.; seawater cooling heat exchanger, marine products piping systems.
Alloy 800 series (Incoloy 800, 800H, and 800HT) are nickel-iron-chromium high-temperature alloys that provide high-temperature strength and resistance to oxidation, carburisation, and other types of high-temperature corrosion. Alloy 800 (UNS N08800), Alloy 800H (UNS N08810), and Alloy 800HT (UNS N08811) have the same nickel, chromium, and iron content, but differ in the level of titanium and aluminium combined (0.85 to 1.2%) to ensure optimum high-temperature properties. The 800HT alloy can be regarded as an improved version of the 800H alloy, with higher carbon content and more tightly controlled aluminium and titanium content, resulting in better mechanical properties and stability at high temperatures.
Incoloy 800 Composition
- Nickel (Ni): 30-35 percent
- Iron (Fe): 39.5% min.
- Chromium (Cr): 19-23 percent
- Aluminium (Al): 0.15-0.60%
- Titanium (Ti): 0.15-0.60 percent
- Carbon (C): 0.10% max.
Incoloy 800H Composition
- Nickel (Ni): 30-35 percent
- Iron (Fe): 39.5% min.
- Chromium (Cr): 19-23 percent
- Aluminium (Al): 0.15-0.60
- Titanium (Ti): 0.15-0.60 percent
- Carbon (C): 0.05-0.10 percent
Incoloy 800HT Composition
- Nickel (Ni): 30-35 percent
- Iron (Fe): 39.5% min.
- Chromium (Cr): 19-23 percent
- Aluminium (Al): 0.15-0.60%
- Titanium (Ti): 0.25-0.60 percent
- Carbon (C): 0.06-0.10 percent
Mechanical Properties
- Density: 7.94 g/c㎡
- Melting range: 1357-1385℃
- Tensile strength: min 550 Mpa
- Yield strength: 0.2% offset, min, 240 Mpa
- Elongation: min 30%
Properties
- Creep and fracture strength: Incoloy 800H and 800HT have significantly higher creep and fracture strength than Incoloy 800. 800H alloys are optimised for stress fracture resistance by controlling the carbon content (0.05-0.10%) and grain size. In contrast, 800HT alloys are further modified in terms of aluminium and titanium content (0.85-1.20%) to ensure optimum performance at elevated temperatures.
- High-temperature performance: Incoloy 800H and 800HT are suitable for high-temperature applications and are typically used above 1,100°F (~593°C) to resist creep and fracture. 800HT will not become brittle, even after prolonged use in the range of 1,200-1,600°F (~649-871°C). become brittle, whereas many stainless steels become brittle in this temperature range. 800HT exhibits excellent cold-forming properties normally associated with nickel-chromium alloys.
- Stress Corrosion Resistance: Incoloy 800H and 800HT have excellent stress corrosion resistance and perform well in high-temperature aqueous media up to 500°C. Their high nickel content allows them to be used in aqueous media for a long period without becoming brittle, which is the case with many stainless steels. Their high nickel content gives them good resistance to stress corrosion cracking under aqueous corrosive conditions. In addition, these alloys have good corrosion resistance in oxidising and non-oxidising salts.
Specifications
- Plate/Sheet/Strip: AMS 5871, ASTM A 240/A 480, ASTM B 409, ASTM B 906
- Seamless pipe, seamless tube: ASTM B 407, ASTM B 829
- Welded Pipe, welded Tubing: ASTM B 515
- Round/Flat Steel: ASTM B 408, ISO 9723
- Fittings: ASTM B 366, ASME SB-366
- Forgings: AMS 5766, ASTM B564
800 VS 800H
- Chemical Composition Differences: Alloy 800H (UNS N08810) contains higher levels of carbon (0.05-0.10%) and higher levels of titanium and aluminium (0.85-1.20%) than alloy 800 (UNS N08800). These compositions have been adjusted to optimise the alloy’s stress rupture properties and high-temperature performance.
- Heat Treated Condition: 800H alloys undergo specific heat treatments to improve their mechanical properties at elevated temperatures, including improved creep and stress rupture characteristics. Such heat treatments typically include solution treatments at higher temperatures, allowing alloy 800H to outperform 800 alloys without such heat treatments in high-temperature environments.
- Application: Due to its superior high-temperature properties, alloy 800H is typically used in more demanding high-temperature environments such as superheater and reheater pipework in power plants, high-temperature reactors and pipework in chemical and petrochemical processes. Alloy 800, on the other hand, is widely used in general high-temperature environments, such as heat-treating equipment and certain chemical industry applications.
- Corrosion Resistance: Both Alloy 800 and 800H have excellent corrosion resistance to a wide range of chemical corrosive media. However, Alloy 800H may exhibit better corrosion resistance in certain environments due to its special heat treatment and chemical composition adjustments.
800H VS 800HT
Carbon Content
- Alloy 800H: Carbon content is usually between 0.05 and 0.10 per cent.
- 800HT alloys: Carbon content is typically between 0.06% and 0.10%, slightly higher than 800H. The increased carbon content improves the high-temperature strength and creep resistance of 800HT alloys.
Aluminium and Titanium Content
- 800H alloys: the content of aluminium and titanium is not particularly strictly controlled, and the total content of aluminium and titanium is usually in the range of 0.30%-1.20%.
- 800HT alloys: Aluminium and titanium contents are more tightly controlled, with total aluminium and titanium contents typically in the range of 0.85%-1.20%. The tighter control gives 800HT alloys better creep resistance and structural stability at high temperatures.
High-Temperature Performance
- 800H alloys: Suitable for high-temperature applications from 600 to 800, they exhibit good creep and stress fracture resistance.
- 800HT alloy: Designed for higher temperature ranges (typically 650 to 1000), it exhibits superior creep and stress fracture resistance at high temperatures.
Heat Treatment and Service Environments
- Alloy 800H: Typically solid solution treated and stabilised for medium to high-temperature applications.
- Alloy 800HT: Undergoes a more rigorous heat treatment process, including solution treatment and stabilisation, and has better properties for use at higher temperatures.
Application
- Alloy 800H: Because of its good performance at moderately high temperatures, it is commonly used in petrochemical equipment, pressure vessels, heat exchangers and some nuclear industry equipment.
- Alloy 800HT: is more suitable for use in extremely high-temperature environments such as industrial furnaces, heat treatment equipment, high-temperature reactors and other equipment that requires long-term exposure to high temperatures.