Selecting the right high-nickel alloy is important to keep the high-temperature industrial equipment running efficiently and safely. Incoloy 840 and Incoloy 800 are two of the most effective materials that engineers often have to choose from. They both are from the nickel-iron-chromium alloy family, with their specific compositions fine-tuned to different extreme conditions. A difference of just a few percentage points in an element can change the alloy’s resistance to heat, stress, or chemical attack. Thus, a beneficial material decision is possible only by understanding these minute yet significant changes. Here is the necessary detailed blog to simplify the technical specifications for better understanding in comparing Incoloy 840 vs. 800. This blog post will cover the different properties, uses, mechanical composition, and chemical composition of these two alloys.
What is Incoloy 840?
Incoloy 840 is a stainless-nickel alloy used in heat processing systems. It offers high temperature resistance and reliable scaling strength, which helps it perform well in cyclic heating. The alloy supports steady oxidation control in service conditions above 980°C. Alloy 840 properties include strong stress resistance in hot environments. Incoloy 840 plate products are preferred for heaters, electric furnaces, and corrosive exhaust systems.
What is Incoloy 800?
Incoloy 800 is an iron-nickel-chromium alloy known for solid mechanical stability at elevated temperatures. It works well in high-pressure and hot chemical media where scaling and cracking often occur. The grade maintains balanced corrosion resistance while preserving tensile strength for long service exposure. It performs well in petrochemical process units, thermal processing, heat exchangers, pressure boilers, and superheater piping.
Applications
Both alloys serve industries that handle extreme heat, corrosive gases, or heated chemicals. Each finds use in different roles based on required toughness, working temperature, and oxidation control.
Incoloy 840
- Electric Heating: Used in heat elements and tubular heaters due to its stable resistance in high-temperature heating setups. Its oxidation strength reduces scaling on continuous heating.
- Heat Treatment: It is preferred for furnace parts in annealing and for industrial heating systems; this alloy resists distortion and maintains stability of structure under repeated temperature cycles.
- Chemical & Petrochemical: Useful for heated chemical lines and exhaust systems that deal with corrosive gases, as its corrosion resistance supports safe handling of acidic fumes.
- Power Generation: Suited for heat exchangers and superheated steam units. The alloy performs well in components facing thermal movement and hot steam pressure.
- Oil & Gas: Used in catalytic converter parts and process heaters. The alloy can withstand the toxic exhaust fumes without surface breakdown.
Incoloy 800
- Petrochemical & Chemical Processing: This alloy is selected for ethylene cracking, pressure piping, and heat exchangers. The alloy will remain stable under hot hydrocarbons and process chemicals.
- Power Generation: Ideal for superheater tubes and boiler parts that require long exposure to heat. Maintains mechanical strength without deformation.
- Heat Treating: Used in furnace muffles, trays, and baskets. It handles continuous heating without scaling or bending.
- Aerospace: It works well with thermal control components, working at extreme high temperatures. Maintains consistent strength throughout high-temperature load cycles.
- Oil & Gas: It is used for processing heaters and refining systems. High resistance to acidic gases protects against hot corrosive processes.
Mechanical Composition Tables
Mechanical properties ensure the metal’s resistance, strength, and ability to bear strain. The table below illustrates the minimum requirements for the common grades of Incoloy 840 and Incoloy 800:
| Property | Incoloy 840 (Min) | Incoloy 800 (Min) | Unit |
| Tensile Strength | 550 | 520 | MPa |
| Yield Strength (0.2% Offset) | 210 | 205 | MPa |
| Elongation (in 4D) | 35 | 30 | % |
| Reduction of Area | 40 | 35 | % |
The data confirms that Incoloy 840 exhibits slightly higher minimum strength values. Its high ductility, indicated by the minimum elongation of 40% in area reduction, shows it can withstand significant deformation without fracturing.
Chemical Compositions
The chemical composition is the root cause of the performance differences between the two alloys. The specific content of nickel and silicon is the primary factor influencing their application suitability.
| Element | Incoloy 840 (%) | Incoloy 800 (%) |
| Nickel (Ni) | 19.0 – 22.0 | 30.0 – 35.0 |
| Chromium (Cr) | 18.0 – 22.0 | 19.0 – 23.0 |
| Iron (Fe) | Balance | Balance |
| Silicon (Si) | 1.50 – 3.00 | Max 1.00 |
| Carbon (C) | Max 0.08 | Max 0.10 |
| Manganese (Mn) | Max 1.50 | Max 1.50 |
| Copper (Cu) | Max 0.50 | Max 0.75 |
The most important distinction is the Nickel content: Incoloy 800 contains significantly more nickel. This increases the corrosion resistance. In contrast, Incoloy 840 is characterized by its much higher silicon range, which is critical for resisting high-temperature oxidation and scaling.
Looking for Incoloy plates, tubes, or heater grade alloys? Rexton Steel & Alloys supplies certified products with material traceability, and strict quality control. Contact for stock sizes, custom orders, and bulk support.
FAQ’s
What is the difference between Incoloy 840 vs 800 heat resistance?
Incoloy 840 provides excellent resistance to surface oxidation and scaling at high temperatures due to its high silicon content. Incoloy 800 offers better strength, and long-term stability under mechanical stress at elevated temperatures.
How do corrosion properties differ?
Incoloy 840 excels at high temperature resistance against surface corrosion like scaling. Incoloy 800 has better overall corrosion resistance across a broader range of corrosive liquid and chemical environments due to its higher nickel content.
What are Incoloy 840’s mechanical properties?
Alloy 840 properties include high minimum tensile and yield strengths, suggesting good load-bearing capacity. The alloy exhibits excellent ductility, often showing a minimum elongation of 40% in the reduction of area.
What are the best applications for each?
Incoloy 840 is ideal for electric heating elements, and furnace components subjected to high temperatures and scaling. Incoloy 800 is better for chemical processing, power generation, and parts that require both high strength and broad chemical resistance.