Incoloy 800H

INCOLOY 800H/HT is an austenitic heat-resistant alloy widely used in high-temperature pressurized structural components. The high strength of 800H/HT is mainly due to the addition of carbon, aluminum, and titanium, and annealing at temperatures as low as 1,149°C to achieve a grain size of ASTM grade 5 or coarser.

Introduction

For 800 H/HT at temperatures up to 787°C, weld with 82 (ER NiCr-3) wire. R A 330-04 (N08334) wire has a matching coefficient of thermal expansion and higher strength. If maximum mechanical strength is desired, it is best to use wire 617 (ERNiCrCoMo-1) or electrode 117 (ENiCrCoMo-1).

In order to avoid cracking of the grain boundaries due to stress relaxation that may occur in 800H/HT welded parts above 538°C, a post-weld heat treatment at 899°C is required, with a holding time of one hour for every 25 mm of material thickness (at least half an hour/25 mm thickness), followed by air-cooling.

Material standard

UNS American Standard: N08811, N08810 W. Nr./EN 

European Standard: 1.4958, 1.4959 

astm: b 409, b 408, b 407 

ASME: SB-409, SB-408, SB-407 Code Case 1325

Material Properties High ASME VIII material design allowable stress values (allowable temperatures up to 1650°F) Good resistance to oxidation at high temperatures (up to 1900°F) Resistance to chloride stress corrosion cracking Major Applications Ethylene Cracker Rapid Cooling Boilers Hydrogen Reformer Stage 1 Lower Collector Pipes, Pig Tail Pipes Gasifier Internals Electric Heating Element Bushings Physical Properties Density: 0.287 lb/in3

Melting point range: 2475- 2525°F

Physical Properties of Incoloy 800H.

Density: 8.0 g/cm3

Melting Point: 1350-1400 °C

Alloy 800H has the following properties:

1. Excellent corrosion resistance in aqueous media at very high temperatures up to 500°C

2. Excellent resistance to stress corrosion

3. Very good workability

Metallographic structure of Incoloy 800H.

800H has a face-centered cubic lattice structure. The extremely low carbon content and increased Ti:C ratio increase structural stability and maximize resistance to sensitization and intergranular corrosion, while low temperature annealing at about 950°C ensures a fine grain structure.

Corrosion resistance of Incoloy 800H.

800H is resistant to many corrosive media. Its high nickel content gives it good resistance to stress corrosion cracking in aqueous corrosive conditions. The high chromium content gives it better resistance to pitting and crevice corrosion cracking. The alloy has good resistance to nitric and organic acid corrosion, but limited corrosion resistance in sulfuric and hydrochloric acids. There is good corrosion resistance in oxidizing and non-oxidizing salts, except in halides where pitting corrosion is possible. It also has good corrosion resistance in water, steam, and mixtures of steam, air, and carbon dioxide.

Application fields

1. Nitric acid condenser--resistant to nitric acid corrosion

2. Steam heating tubes - very good mechanical properties

3. Heating element tubes - good mechanical properties

For applications up to 500°C, the alloy is supplied in annealed condition.