Alloy 800, Alloy 800H, Alloy 800HT
Alloy 800 (UNS N08800), Incoloy 800H (UNS N08810), and Incoloy 800HT (UNS N08811) are nickel-iron-chromium superalloys with excellent high-temperature strength, oxidation resistance, and carburization resistance. They are widely used in chemical processing, power generation, and heat treatment industries.
Table of Contents
What is Alloy 800, Alloy 800H, Alloy 800HT?
The Incoloy 800 group of alloys is an Iron-Nickel-Chromium alloy with high strength and oxidation resistance at high temperatures. The relatively high Chromium content (19-23%) provides the alloy with good aqueous corrosion resistance. The Nickel (30-35%) provides the resistance to stress corrosion cracking (SCC), chloride pitting, and general corrosion. This alloy is capable of retaining its metallurgical stability in a wide range of temperatures.
This group consists of three alloys with slightly different properties and applications:
- Incoloy 800 is the basic variant, without special Al and Ti content, commonly used in applications up to 600°C.
- Incoloy 800H has a higher carbon content (0.05-0.10%) and an annealing process at high temperatures to obtain larger grain sizes, which greatly increases creep and stress rupture strength. The minimum Al and Ti content is 0.15-0.6%.
- Incoloy 800HT has an even higher combined Titanium and Aluminum content (0.85-1.20%) which gives the alloy optimal high-temperature properties. Incoloy 800HT also has a carbon range of 0.06-0.10% and is solution annealed.
Applications
Typical applications for Incoloy 800 / 800H / 800HT include:
- Heat exchangers
- Pressure vessels
- Industrial furnaces
- Heat-treatment equipment
- Components for power plants
- Ethylene pyrolysis tubing
- Sheathing for heating elements
- Carburizing equipment
- Chemical and petrochemical processing equipment
Chemical Composition (%)
| Standard | Grade | Fe: | Ni: | Cr: | Ti: | Al: | Mn: | Cu: | Si: | C: | P: | S: | Comments: |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UNS | alloy 800,UNS N08800,Incoloy 800 |
>39.5 | 30.0-35.0 | 19.0-23.0 | 0.15-0.60 | 0.15-0.60 | <1.5 | <0.75 | <1.0 | <0.1 | <0.045 | <0.015 | - |
| EN | 1.4876, X10NiCrAlTi32-21 |
Balance | 30.0-34.0 | 19.0-23.0 | 0.15-0.60 | 0.15-0.60 | <2.0 | - | <1.0 | <0.12 | <0.03 | <0.015 | - |
| ISO | FeNi32Cr21AlTi,NW8800 |
Balance | 30.0-35.0 | 19.0-23.0 | 0.15-0.60 | 0.15-0.60 | <1.5 | <0.7 | <1.0 | 0.05-0.10 | - | <0.015 | - |
| UNS | alloy 800H,N08810,Incoloy 800H |
>39.5 | 30.0-35.0 | 19.0-23.0 | 0.15-0.60 | 0.15-0.60 | <1.5 | <0.75 | <1.0 | 0.05-0.10 | <0.045 | <0.015 | - |
| EN | 1.4958,X5NiCrAlTi31-20 |
Balance | 30.0-32.5 | 19.0-22.0 | 0.2-0.5 | 0.2-0.5 | <1.5 | <0.75 | <1.0 | 0.05-0.10 | <0.045 | <0.015 | Al+Ti<0.70; Ni+Co:30.0-32.5 |
| UNS | alloy 800HT,N08811,Incoloy 800HT |
>39.5 | 30.0-35.0 | 19.0-23.0 | 0.15-0.60 | 0.15-0.60 | <1.5 | <0.75 | <1.0 | 0.06-0.10 | <0.045 | <0.015 | Al+Ti: 0.85-1.20 |
| EN | 1.4959, X8NiCrAlTi32-21 |
Balance | 30.0-34.0 | 19.0-22.0 | 0.25-0.65 | 0.25-0.65 | <1.5 | <0.5 | <0.7 | 0.05-0.10 | <0.015 | <0.01 | Ni+Co:30.0-32.5; N<0.03; Co<0.5 |
| EN | 1.4558, X2NiCrAlTi32-20 |
Balance | 32.0-35.0 | 20.0-23.0 | <0.6 | 0.15-0.45 | <1.0 | - | <0.7 | <0.03 | <0.02 | <0.015 | Ti>8*(C+N) |
| NF | Z10NC32-21 |
Balance | 30.0-35.0 | 19.0-23.0 | 0.15-0.60 | 0.15-0.60 | <2.0 | - | <0.75 | <0.1 | <0.035 | <0.015 | - |
| NF | Z8NC33-21 |
Balance | 30.0-35.0 | 19.0-23.0 | 0.15-0.60 | 0.15-0.60 | <2.0 | - | <0.75 | 0.05-0.10 | <0.035 | <0.015 | - |
| BS3072-BS3076 | NA15-NA15H |
Balance | 30.0-35.0 | 19.0-23.0 | 0.15-0.60 | 0.15-0.60 | <1.5 | <0.75 | <1.0 | <0.1 | - | <0.015 | Ni:Ni+Co |
| GOST | Ch20N32T,EP670,ChN32T |
Balance | 30.0-35.0 | 19.0-23.0 | 0.15-0.60 | 0.15-0.60 | <1.5 | - | <0.5 | 0.05-0.10 | <0.035 | <0.015 | - |
Material Properties
- Density: 8.03 g/cm3
- First melting temperature: 1350 °C
- Precipitation temperature: 760 °C
Room temperature mechanical properties of Incoloy 800 bar:
- Tensile strength: 520 MPa
- Yield strength: 220 MPa
- Elongation: 45%
Room temperature mechanical properties of Incoloy 800H bar:
- Tensile strength: 550 MPa
- Yield strength: 240 MPa
- Elongation: 45%
Room temperature mechanical properties of Incoloy 800HT bar:
- Tensile strength: 560 MPa
- Yield strength: 250 MPa
- Elongation: 45%
Elevated temperature (870°C) mechanical properties of Incoloy 800H bar:
- Tensile strength: 120 MPa
- Yield strength: 70 MPa
- Elongation: 35%
Rupture strength of Incoloy 800H bar and temperature:
- 760°C: 130 MPa
- 870°C: 60 MPa
- 980°C: 30 MPa
Corrosion behaviour
Aqueous corrosion - good general resistance in oxidizing and reducing environments.
Stress corrosion cracking - generally very good resistance. The list of known environments that cause SCC in alloy 800:
- 155°C 42% MgCl2
- 155°C 42% MgCl2
- Boiling 85% ZnCl2
Incoloy 800 has very good resistance to SCC in polythionic acid solutions, but wrong heat treatment (holding at 650°C) may lead to sensitisation and low scc resistance. It has also exceptional resistance to SCC in high-temperature water and dilute aqueous solutions. alloy 800 may be a better choice for tubing materials in steam generators of pressurized nuclear water reactors.
High-temperature tests - due to iron base, alloy 800 is generally not resistant to temperatures above 670°C, and alloy 800H as well as 800HT are only comparatively better. Nickel-base alloys are much better in this regard.
High-temperature oxidation - medium resistance of alloy 800H and alloy 800HT. Rather poor resistance at temperatures above 925°C, as confirmed by test results:
Average metal affected after 1008h of static oxidation test at indicated temperatures (alloy 800H):
- 980°C: 0.046 mm
- 1095°C: 0.19 mm
- 1150°C: 0.23 mm
- 1205°C: 0.35 mm
Metal loss after 500h of dynamic oxidation test in high-velocity combustion stream at 1090°C equaled 0.77mm (alloy 800H), which is very high.
High-temperature carburization - mediocre resistance, that can be acceptable in some allowances. Nickel based alloys fare noticeably better. Carbon absorption results for alloy 800H in high-temperature tests:
- Ar-5H2-5CO-5CH4 215 h; 870°C: 0.5
- Ar-5H2-5CO-5CH4 215 h; 930°C: 1
- Ar-5H2-5CO-5CH4 55 h; 980°C: 1
- Ar-5H2-5CO-5CH4 24 h; 1090°C: 12.6
- H2-2CH4 100 h (alloy 800); 1000°C: 19
High-temperature nitridation - mediocre resistance. Alloy 800 is not resistant to high temperature nitridation. It corrodes strongly even in pure nitrogen at temperatures above 980°C. Pure nitrogen, however, does not cause problems to alloy 800H and 800 HT. These two alloys, however, are not resistant to high-temperature ammonia. The results of the nitrogen absorption test for the alloy alloy 800H are as follows:
- Ammonia 168 h; 650°C: 4.3
- Ammonia 168 h; 980°C: 4.0
- Ammonia 168 h; 1090°C: 5.5
High-temperature sulfidation - poor resistance. Due to high chromium content and presence of titanium, alloy 800H resists sulfidation for some time, but after few thousand hours rapid breakaway corrosion happens.
High-temperature halogenation - poor resistance, which is evident from the weight-loss experienced after following tests (alloy 800H):
- Ar-30Cl2 500 h; 400°C: 6
- Ar-30Cl2 500 h; 500°C: 13
- Ar-30Cl2 500 h; 705°C: 200-270
- Ar-20O2-0.25Cl2 400 h; 900°C: 26.91
- Ar-20O2-0.25Cl2 400 h; 1000°C: 87.05
Hot corrosion - poor resistance, alloy 800 / 800H / 800HT cannot be used for gas turbines.
Ash/salt deposit corrosion - adequate resistance and alloy 800H is widely used in coal-fired boilers. In a field test when uncooled specimens were exposed in the superheated section at 815°C in a boiler fired with high vanadium Bunker C fuel, measured corrosion rate was 9-12 mm/year.
Physical Properties
- Density: 8.03 g/cm3
- First melting temperature: 1350 °C
- Precipitation temperature: 760 °C
Heat Treatment
Recommended working and heat treatment parameters:
- Hot working: 1205 °C
- Heavy forging: 1010 °C
- Light forging: >870 °C
- First melting temperature: 1260 °C
- Precipitation temperature: 760 °C
- Batch annealing in bell-type furnaces:
Cool rapidly through the range between 760-540°C to ensure freedom from sensitization. Alloy 800 is not susceptible to thermal cracking.
Machining - the alloy 800 / alloy 800H / alloy HT is best machined in the cold-drawn or cold-drawn and stress-relieved conditions.
Processing Performance
Weldability
Weldability - alloy 800 belongs to group 45 according to ISO 15608. For brazing, p-number is equal 111, according to ASME, section IX.
Selection of welding consumables for alloy 800:
- Filler metals: ERNiCr-3
Selection of welding consumables for alloy 800H and alloy 800 HT:
- Coated electrodes: ENiCrCoMo-1
- Filler metals: ERNiCr-3 or ERNiCrCoMo-1
Hot-cracking - the alloy is sensitive to hot-cracking due to high iron content. However, one study has found that reducing the aluminum plus titanium content to <0.06% essentially eliminated hot-cracking. It can further mean that alloy 800H and alloy 800HT are more susceptible to hot-cracking due to typically higher Al+Ti content.
Electropolishing
Electropolishing - electrolyte composition: 37 ml of H3PO4, 56 ml of glycerol. Platinum cathode. 3.1 A/cm2.
Alternative Names, Equivalents, and Other Designations
- 1.4558
- alloy 800
- Ch20n32t
- f-3314
- FeNi32Cr21AlTi
- INCOLOY 800
- N08800
- NW8800
- SANICRO 30
- une f-3314
- x2nicralti32-20
- z10nc32-21
- BOHLER H500
- EMVAC 800
- DMV 4958
- DMV 4959
- NY800
- PYRAD 33
- VLX 800
- CHRONIMO 1.4876
- CRONIDUR 4959
- Coralloy 800
- HAYNES 800
- NY 811
- NAS 800
- NCF800
- SINOXX 4876
- UNITEMP 800
- AL800
- F-3314
- Ch20N32T
- EP670
- ChN32T
- NCF800H
- NCF800HTB
- NCF800HTF
- NCF800HTP
- NCF800TB