A nickel-iron-chromium alloy, 800H/AT is designed for high temperature structural applications

Alloy 800H/AT is an austenitic heat resistant alloy designed for high temperature structural applications. The strength of 800H/AT is achieved by controlled levels of carbon, aluminum and titanium along with a 1148°C minimum anneal to achieve a grain size of ASTM 5 or coarser.

  • UNS Number: N08810, N08811
  • Werkstoff Number: 1.4958, 1.4959
  • ASTM: B 407, B 408, B 409
  • Other: ASME: SB 407 Code Case 1325, SB 408, SB 409

Product availability

Pipe (Seamless)
Pipe Fittings
Round Bar

Chemical analysis



  • Super-heaters and re-heater tubing
  • Reformer outlet pigtails and manifolds
  • Heat exchangers
  • Pressure vessels
  • Dampers
  • Industrial furnaces

About 800H/AT

With close control of the carbon, aluminium and titanium contents combined with the high temperature anneal, 800H/AT has significantly higher creep-stress rupture strength than Alloy 800.

This alloy is commonly welded using RA82 (ERNiCr-3) bare wire for applications under 788°C. RA330-04 (UNS N08334) bare filler wire offers a closer match than RA82 based on the thermal expansion coefficient and higher strength. For maximum strength alloy 617 (ERNiCrCoMo-1) bare wire or 117 (ENiCrCoMo-1) covered electrodes are suggested.

To avoid possible stress relaxation grain boundary cracking in applications above 538°C the welded fabrication may be heat treated at 899°C for approximately one hour per inch of thickness or 30 minutes minimum followed by air cooling.

  • Density: 7.94 g/cm³
  • Melting Range: 1357 – 1385°C
  • Specific Heat Capacity: 460 J/kg°C (0-100°C)
  • Curie Temperature: -115°C

Mechanical & Physical Properties

Mechanical & Physical Properties 21.1°C537.8°C649°C760°C871°C982°C
Ultimate Tensile Strength /MPa530.9437.8384222.7128.270.3
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