Alloy 800H

Titanium

Nickel

Overview

Grades & Materials

Pure Nickel

Nickel–Chromium Alloys

Nickel–Molybdenum Alloys

Nickel–Chromium–Molybdenum Alloys

Nickel–Iron Alloys

Alloy 800

Alloy 800H

Alloy 800HT

Applications

Products

Standards & Quality

Technical Knowledge

Selection Guide

Stainless

Carbon

Alloy

Copper, Brass and Bronze

Alloy 800H

Alloy 800H is a nickel–iron–chromium (Ni–Fe–Cr) alloy specifically developed for improved creep and rupture strength at elevated temperatures.
It is an enhanced version of Alloy 800, achieved through controlled carbon content and grain size, making it suitable for pressure equipment and continuous high-temperature service.

Within the Nickel–Iron alloy family, Alloy 800H is positioned as the high-temperature pressure-grade, bridging the gap between Alloy 800 and Alloy 800HT.

Chemical & Metallurgical Characteristics

Alloy 800H shares the same base Ni–Fe–Cr chemistry as Alloy 800, but with tighter metallurgical controls.

Key Metallurgical Features

  • Controlled carbon range to improve creep strength

  • Coarse, stabilized austenitic grain structure

  • Nickel stabilizes the FCC structure at high temperature

  • Chromium improves oxidation and carburization resistance

These controls allow Alloy 800H to maintain mechanical integrity under long-term thermal stress.

High-Temperature & Creep Performance

Alloy 800H is designed for pressure service at elevated temperatures, where creep resistance becomes critical.

Excellent Performance In:

  • Long-term high-temperature operation

  • Pressure vessels and piping

  • Steam and hydrocarbon processing

  • Carburizing and oxidizing atmospheres

Compared with Alloy 800:

  • Higher allowable stress at elevated temperatures

  • Improved creep rupture strength

  • Better suitability for ASME pressure design

Corrosion Resistance Behavior

Typical Performance

  • Good resistance in oxidizing and carburizing environments

  • Suitable for steam, hydrocarbons, and non-aggressive media

Limitations

  • Not intended for strong acids or chlorides

  • Corrosion resistance is secondary to thermal-mechanical performance

Alloy 800H is selected primarily for mechanical reliability, not aggressive chemical resistance.

Mechanical Properties (Typical)

Alloy 800H provides:

  • Improved creep and rupture strength vs. Alloy 800

  • Good tensile and yield strength at elevated temperatures

  • Stable ductility under thermal cycling

These properties make it suitable for ASME-coded pressure equipment.

Typical Applications

Alloy 800H is widely used in high-temperature, pressure-containing equipment.

Common Applications Include:

  • Heat exchanger tubing

  • Pressure vessels and headers

  • Petrochemical and refining heaters

  • Steam generators and superheaters

  • High-temperature piping systems

It is commonly specified when design codes require minimum creep strength.

Product Forms Available

Alloy 800H is commonly supplied as:

  • Seamless tubes

  • Pipes

  • Plates and sheets

  • Bars and rods

  • Forgings and tube sheets

For thermal and pressure equipment, seamless Alloy 800H tubes are widely specified due to:

  • Uniform wall thickness

  • Reliable pressure performance

  • Stable high-temperature behavior

Manufacturing & Fabrication

Alloy 800H can be fabricated using standard nickel-alloy practices:

  • Hot and cold working

  • Solution annealing

  • Conventional welding procedures

Proper heat treatment and grain-size control are essential to ensure creep performance.

Standards & Specifications

Alloy 800H products are commonly supplied in accordance with:

  • ASTM material standards

  • ASME Boiler & Pressure Vessel Code

  • Project-specific technical requirements

Typical Inspection & Testing:

  • Chemical composition analysis

  • Mechanical and creep-related testing

  • Dimensional inspection

  • Eddy current or ultrasonic testing (for tubes)

  • PMI verification

Full Mill Test Certificates (MTC) and traceability are standard.

Alloy 800H vs Alloy 800 / 800HT (Concept)

  • Alloy 800

    • General high-temperature stability

    • Lower creep strength

  • Alloy 800H

    • Controlled carbon and grain size

    • Improved creep and rupture strength

    • Preferred for pressure service

  • Alloy 800HT

    • Additional aluminum/titanium control

    • Highest creep resistance in the 800 series

Selection depends on temperature, pressure, and code requirements.

Summary

Alloy 800H is positioned within Nickel → Grades & Materials → Nickel–Iron Alloys and is selected for high-temperature pressure applications requiring improved creep strength.

Explore next:

  • Grades: Alloy 800 · Alloy 800HT

  • Applications: Heat Exchangers · Power Generation

  • Guide: Nickel Selection Guide