Incoloy 800 and 800H/HT are different variants of the same base alloy. The main differences lie in carbon content, heat treatment process, and high-temperature performance.

In simple terms, 800H/HT is a refined version of 800. It contains more carbon and undergoes a stricter heat treatment. This combination creates a coarse-grain structure, which gives 800H/HT far better resistance to creep at high temperatures.

Differences

Property	Incoloy 800 (UNS N08800)	Incoloy 800H (UNS N08810)	Incoloy 800HT (UNS N08811)
Carbon Content	0.03% – 0.10% (medium)	0.05% – 0.10% (higher)	0.06% – 0.10% (highest)
Al + Ti Content	≥ 0.30%	≥ 0.30%	≥ 0.85% (enhanced)
Heat Treatment	Annealed above carbide solubility temperature, followed by rapid cooling	Must be annealed at a minimum of 2100°F (1149°C), then rapidly cooled	Same as 800H, annealed at ≥ 2100°F (1149°C), then rapidly cooled
Grain Size	No mandatory requirement	ASTM 5 or coarser (larger grain size)	ASTM 5 or coarser (larger grain size)
Key Features	Balanced performance, excellent corrosion resistance	Improved high-temperature creep and rupture strength	Further enhanced high-temperature strength and creep resistance due to higher Al+Ti
Common Applications	Chemical processing, heat exchanger tubes, nitric acid production units	High-temperature furnace components, cracking furnace tubes, heat exchangers, radiant tubes	Severe high-temperature environments such as petrochemical cracking furnace outlets

The Core Difference

The biggest difference is in high-temperature performance, which is also the most important factor for material selection.

The mechanical properties of Incoloy 800 and 800H/HT may be similar at room temperature, but at elevated temperatures (typically above 600°C / 1112°F), the performance gap becomes significant:

• 800H and 800HT offer much better high-temperature strength, creep resistance, and rupture resistance compared with standard 800.
• 800HT, with its higher Al+Ti content, generally delivers the best high-temperature performance among the three.

For applications where long-term strength at extreme temperatures is critical, 800H and 800HT are superior choices.

Application Fields

Incoloy 800 is suitable for:

• Reactors and piping in chemical plants
• Heater tubes and exchangers in nitric acid production
• Superheater tubes in nuclear facilities

Incoloy 800H/HT is tailored for:

• Ethylene cracking furnace tubes
• Radiant tubes and combustion chambers
• Industrial kilns and reformer tubes
• High-temperature heat exchangers

Material Selection Guide

1. Incoloy 800 – A versatile alloy with reliable corrosion and heat resistance. Best for balanced performance.
2. Incoloy 800H – An upgraded grade with higher carbon and controlled heat treatment. Designed for strength under stress at high temperature.
3. Incoloy 800HT – The top tier in this series. Enhanced with more Al+Ti for the highest resistance to creep and rupture.

If you need Incoloy alloy products, our sales team can provide detailed specifications. Ordering directly from us ensures reliable service and competitive pricing.