Incoloy alloy 800, Incoloy 800H, and Incoloy 800HT are three closely related alloys within the Incoloy family, distinguished by their similar names.
These alloys share many characteristics, with only slight differences in their carbon, aluminum, and titanium content.
In this article, we will explore the relationships and differences among these three alloys.
Incoloy Alloy 800
Before the development of Incoloy 800, Inconel 600 was widely used in various high-temperature and high-corrosion applications, thanks to its high nickel and chromium content.
However, as the value of nickel became more recognized and its relative scarcity in many countries became apparent, nickel evolved into a strategic material, leading to a rise in its price.
To address the increasing cost of nickel, there was a need for materials with lower nickel content to partially replace Inconel 600 in high-temperature applications. This led to the creation of Incoloy 800.
Incoloy 800 features a lower nickel content and a higher iron content compared to Inconel 600, significantly reducing material costs. The developers ensured that Incoloy 800 maintained excellent resistance to high temperatures and corrosion while being more cost-effective.
Incoloy 800H
When Incoloy 800 was first introduced, it was available in two grades. The standard Incoloy 800 was known as Grade I. To enhance the creep strength and fracture strength for certain applications, a high-carbon variant was developed, initially called Incoloy 800 Grade II.
Over time, Grade II underwent numerous improvements, evolving significantly in chemical composition, heat treatment processes, and grain size requirements, distinguishing it from Grade I. This led to the establishment of a new grade, Incoloy 800H, which offers superior creep fracture resistance. Incoloy 800H now plays an indispensable role in specific high-demand applications.
Incoloy 800HT
After the official introduction of Incoloy 800H, it gained widespread recognition from manufacturers, leading to an increase in the number of producers capable of making this alloy.
Among these manufacturers, Special Metals, the original developer of Incoloy 800, continues to produce Incoloy 800H at a higher quality than others. They are industry leaders in enhancing the creep resistance of their alloys.
Special Metals achieved this by implementing stricter controls over the carbon, aluminum, and titanium content in their Incoloy 800H, resulting in the creation of Incoloy 800HT.
Similarities among Incoloy Alloy 800, 800H and 800HT
Standards
1. ASTM A240 – Plate, Sheet and Strip
2. ASTM A480 – Plate, Sheet and Strip
3. ASTM B163 – Condenser and Heat Exchanger Tube
4. ASTM B366 – Welded Fittings
5. ASTM B407 – Seamless Pipe & Tube
6. ASTM B408 – Rod and Bar
7. ASTM B409 – Plate, Sheet and Strip
8. ASTM B514 – Welded Pipe
9. ASTM B515 – Welded Tube
10. ASTM B564 – Forgings
11. ASTM B751 – Welded Tube
12. ASTM B775 – Welded Pipe
13. ASTM B829 – Seamless Pipe & Tube
14. ASTM B906 – Plate, Sheet and Strip
The three alloys have essentially the same implementation standards, where they are defined as UNS N08800 (Incoloy 800), UNS N08810 (Incoloy 800H) and UNS N08811 (Incoloy 800HT) respectively.
Types
Although all three alloys contain aluminium and titanium, these elements are added only to improve the properties of the alloy and do not have a precipitation strengthening effect.
Brands
All three alloys are generally distinguished by the INCOLOY® brand.
Use Temperature
Incoloy Alloy 800, Incoloy Alloy 800H, and Incoloy Alloy 800HT are widely used for high temperature.
Differences among Incoloy Alloy 800, 800H and 800HT
Chemical Composition
| Element | Alloy 800 | Alloy 800H | Alloy 800HT |
| C | 0.10 max | 0.05 – 0.10 | 0.06 – 0.10 |
| Mn | 1.50 max | 1.50 max | 1.50 max |
| Si | 1.00 max | 1.00 max | 1.00 max |
| S | 0.015 max | 0.015 max | 0.015 max |
| Cu | 0.75 max | 0.75 max | 0.75 max |
| Fe | 39.50 min | 39.50 min | 39.50 min |
| Ni | 30.00 – 35.00 | 30.00 – 35.00 | 30.00 – 35.00 |
| Cr | 19.00 – 23.00 | 19.00 – 23.00 | 19.00 – 23.00 |
The other chemical composition of the three materials is completely indistinguishable, which makes them not very different in terms of overall heat and corrosion resistance and physical properties.
Mechanical Properties
| Inconel 800 | Inconel 800H & 800HT | ||
|---|---|---|---|
| Cold-worked Annealed | Hot-finished Annealed | Cold-worked / Hot-finished Annealed | |
| Tensile Strength, MPa, min | 520 | 450 | 450 |
| Yield Strength, MPa, min | 205 | 170 | 170 |
| Elongation, %, min | 30 | 30 | 30 |
Conclusion
Incoloy 800, Incoloy 800H, and Incoloy 800HT share many similarities.
Their primary differences lie in the varying levels of carbon, aluminum, and titanium, which impact their creep strength.
We manufacture Incoloy 800, Incoloy 800H, and Incoloy 800HT to precise standards. Feel free to contact us with your specific needs.
