Incoloy 800H/UNS N08810/W.Nr. 1.4958/Alloy 800H bar

Incoloy 800H bar, designated as UNS N08810, material number W.Nr. 1.4958, and commonly known as Alloy 800H, is a controlled-carbon version of Incoloy 800 specifically designed for improved high-temperature strength and creep resistance. This bar stock form is optimized for long-term service in applications involving temperatures from 600°C to 1100°C (1110°F to 2000°F), such as furnace components, heat exchangers, and reformer tubes in petrochemical and power generation industries. Its enhanced properties come from controlled chemistry and a specific grain structure.

Introduction to Incoloy 800H (Alloy 800H)

Incoloy 800H is an austenitic nickel-iron-chromium alloy distinguished from standard Alloy 800 by its higher carbon content, tighter control of aluminum and titanium ratios, and a mandatory solution annealing heat treatment at a minimum temperature to achieve a coarse grain size. This controlled coarse grain structure is key to providing superior creep and stress-rupture properties at high temperatures. The bar stock is essential for components subjected to high stress under prolonged thermal exposure.

Chemical Composition of Incoloy 800H Bar

The high-temperature capability of Incoloy 800H bar is ensured by its specific compositional limits and controls. Supplied by Shanghai NC Metal Materials Co., Ltd., the bar stock meets stringent specifications that mandate the properties necessary for creep-resistant service.

Mechanical Properties of Incoloy 800H Bar

Incoloy 800H bar is characterized by its high-temperature strength and creep resistance, which are superior to standard Alloy 800. Properties are ensured through a mandatory high-temperature solution anneal.

Typical Creep Rupture Strength (100,000h)

Physical Properties of Incoloy 800H Bar

The physical properties of Alloy 800H bar are nearly identical to Alloy 800 and are critical for high-temperature system design.

Notes / Condition

Standard Specifications, Bar Forms, and Available Sizes

Shanghai NC Metal Materials Co., Ltd. supplies Incoloy 800H bar with the mandatory heat treatment and grain size control for high-temperature structural applications.

Primary Applications of Incoloy 800H Bar Stock

Machined or forged components from Incoloy 800H bar are used in the most demanding high-temperature, high-stress applications: Petrochemical Processing: Catalytic reformer furnace tubes, pigtails, outlet headers, and steam methane reformer tubes where creep resistance under high pressure and temperature is critical. Power Generation: Superheater and reheater support brackets, heat exchanger tubing, and boiler components in conventional and nuclear plants. Industrial Heating: Radiant tubes, muffles, and fixtures for high-temperature heat treatment furnaces, especially where load-bearing at temperature is required. Heat Recovery Systems: Components in primary surface and plate-type heat exchangers.

Heat Treatment and Grain Size Control

The defining characteristic of Incoloy 800H is its mandatory heat treatment. The material must be solution annealed at a temperature of at least 1149°C (2100°F) for a sufficient time to dissolve carbides and produce a coarse austenitic grain size (typically ASTM No. 5 or coarser). This coarse grain structure is essential for maximizing creep rupture strength and ductility at high operating temperatures. This treatment is performed by the material producer (e.g., Shanghai NC Metal Materials Co., Ltd.) and is verified by grain size testing.

Machining and Fabrication of Incoloy 800H Bar

Machining Incoloy 800H bar requires techniques for high-temperature austenitic alloys. Its coarse grain structure can make it slightly more abrasive than fine-grained materials. Recommendations include: using rigid machine setups; sharp carbide tools with positive rake angles; moderate speeds and feeds; and ample coolant. It is generally machinable in the solution-annealed condition. Welding is possible but requires subsequent solution annealing to restore the coarse grain structure and creep properties in the heat-affected zone, which is often impractical for fabricated structures.

Differences Between Alloy 800, 800H, and 800HT

It is crucial to distinguish between these grades: Alloy 800: Standard grade with lower carbon (C ≤ 0.10%) and no grain size requirement. Alloy 800H: Controlled higher carbon (0.05-0.10%), requires solution anneal ≥1149°C and coarse grain size (ASTM 5 or coarser) for creep resistance. Alloy 800HT (UNS N08811): Similar to 800H but with tighter control of Al and Ti, requiring (Al + Ti) ≥ 0.85% for even higher strength. Bar stock from Shanghai NC Metal Materials Co., Ltd. is supplied to the specified grade requirements.

Reference Pricing and Key Purchasing Factors

The price of Incoloy 800H bar from Shanghai NC Metal Materials Co., Ltd. reflects its specialized heat treatment and controlled chemistry for high-temperature service.