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Incoloy800HT

Updated: 2026-07-21

Overview

Incoloy 800HT is a controlled-composition variant of Incoloy 800, optimized for high-temperature service through tighter control of titanium, aluminum, and carbon content. Developed by Special Metals Corporation, this alloy belongs to the nickel-iron-chromium family and is distinguished by its exceptional resistance to oxidation and carburization at temperatures up to 815°C (1500°F). The 'HT' designation indicates its enhanced high-temperature properties, particularly creep and rupture strength. While maintaining good fabricability, 800HT offers superior performance compared to standard 800/800H alloys in prolonged high-heat applications, making it a preferred choice for critical components in energy and process industries.

Physical and Chemical Properties

Incoloy 800HT exhibits a face-centered cubic (FCC) crystal structure that remains stable across its service temperature range. Its typical room temperature tensile strength ranges from 450-600 MPa, with yield strength of 170-300 MPa, while maintaining elongation of 30-45%. The alloy's thermal expansion coefficient is approximately 14.4 μm/m°C (20-100°C range). Chemically, the alloy forms a protective chromium oxide surface layer that resists scaling in oxidizing atmospheres. Its nickel content provides resistance to chloride stress corrosion cracking, while the balanced composition minimizes σ-phase formation during prolonged high-temperature exposure. The controlled carbon content (0.06-0.10%) enhances creep resistance without compromising weldability.

Main Applications

The primary use of Incoloy 800HT is in high-temperature industrial equipment, particularly for components requiring both heat resistance and mechanical strength. Common applications include radiant tubes, muffles, and retorts in heat treatment furnaces, pyrolysis furnace tubes in ethylene production, and superheater tubes in power plants. In chemical processing, it serves in steam methane reformer components, catalyst support grids, and high-temperature heat exchangers. The nuclear industry utilizes 800HT for steam generator tubing and reactor internals due to its combination of corrosion resistance and low neutron absorption cross-section. Emerging applications include concentrated solar power systems and advanced combustion systems.

Safety and Storage

In solid form, Incoloy 800HT poses minimal health risks, requiring standard metal handling precautions. However, machining operations generate fine metallic dust that may irritate respiratory systems - use local exhaust ventilation and PPE as per OSHA guidelines. No special storage conditions are required beyond protection from mechanical damage and corrosive environments. For welding and hot working, adequate ventilation is essential to prevent inhalation of fumes containing nickel and chromium compounds. The alloy does not require hazardous material labeling for transportation under normal conditions, but cutting debris should be collected and recycled to prevent environmental contamination from heavy metal accumulation.

B2B Procurement Guide

When procuring Incoloy 800HT, specify the required product form (plate, sheet, tube, etc.) and dimensional tolerances according to relevant ASTM/ASME standards. Mill test reports should verify chemical composition and mechanical properties, with special attention to carbon, titanium, and aluminum content for high-temperature applications. Lead times can be significant (8-12 weeks for mill orders), so plan procurement accordingly. For fabricated components, ensure suppliers have experience with nickel alloys - improper welding or heat treatment can compromise performance. Consider third-party inspection for critical applications. Price fluctuations follow nickel commodity markets, with surcharges typically comprising 30-50% of total cost.

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