Material Family

Nickel-Iron-Chromium Austenitic Alloy (Solid-Solution Strengthened)

An economical alloy for high-temperature service, with a lower nickel content than Inconel grades.

Common Designations

800: UNS N08800, Incoloy 800, W.Nr. 1.4876
800H: UNS N08810, Incoloy 800H
800HT: UNS N08811, Incoloy 800HT

The "H" (High-Temperature) and "HT" (High-Temperature with Titanium) grades are specified for enhanced creep strength. "Incoloy" is a trademark of Special Metals Corporation.

Chemical Composition (Typical wt.%)

Ni: 30.0 - 35.0
Cr: 19.0 - 23.0
Fe: ≥ 39.5 (Balance)
Al: 0.15 - 0.60
Ti: 0.15 - 0.60
C:
• 800: ≤ 0.10
• 800H: 0.05 - 0.10
• 800HT: 0.06 - 0.10

High Iron (Fe) content makes it more economical. Balanced Ni/Cr provides oxidation resistance and stability. Controlled C, Al, Ti are critical for the strength of H/HT grades.

Mechanical Properties (Annealed Plate, Room Temp)

Tensile Strength (Rm): 520 - 690 MPa
Yield Strength (Rp0.2): 205 - 345 MPa
Elongation (A): 30 - 45%

Good ductility and moderate strength. The key advantage is strength retention at high temperatures.

Physical Properties

Density: 7.94 g/cm³
Melting Range: 1350 - 1400 °C
Recommended Continuous Service Temp: Up to ~700°C (1300°F) for general corrosion; H/HT grades are designed for long-term service above 540°C (1000°F).

Distinction: Standard 800 is for general corrosion; 800H/HT are for high-temperature, high-strength applications.

Key Performance Attributes

• Excellent resistance to oxidation, carburization, and sulfidation.• Good resistance to chloride stress corrosion cracking and aqueous corrosion.• Good strength and workability.• 800H/HT: Superior and predictable creep rupture strength at high temperatures.

An excellent all-rounder for petrochemical and power industry heat exchangers and piping.

Key Standards (Plate)

ASTM B409 / ASME SB-409 (Primary plate spec),
800H/HT must also meet ASTM B407 for grain size requirements.

ASTM B409 covers all three grades; 800H/HT have additional mandatory heat treatment and grain size controls per ASTM B407.

Heat Treatment (Critical for H/HT)

800H: Must be annealed at a minimum of 1121°C (2050°F) to achieve an ASTM grain size of 5 or coarser.
800HT: Same as 800H, plus must meet a specific (Al+Ti) content (0.85-1.20%) for optimized creep strength.

This controlled anneal is essential to develop the large grain structure that provides the enhanced creep resistance.

Typical Applications

• Heat Exchanger Tubes & Tubesheets (Shell & Tube)
• Petrochemical Cracking Furnace Tubes & Piping (800H/HT)
• Power Plant Superheater & Reheater Tubes
• Industrial Furnace Components & Retorts
• Nuclear Steam Generator Tubing

The most common application is in tubular heat exchangers and furnace systems across the power and chemical industries.