Incoloy 800 vs 800H vs 800HT: Which Grade Do You Need?
At FULLERKREG, we frequently field questions about the differences between Incoloy 800, Incoloy 800H, and Incoloy 800HT. These three nickel-iron-chromium alloys share the same base composition but differ in carbon content, titanium-to-aluminum ratio, and resulting high-temperature creep strength. Choosing the wrong sub-grade can lead to premature failure in elevated-temperature service.
This guide provides a direct technical comparison of all three grades per ASTM B408, covering chemical composition and mechanical properties so you can make the right selection for your application.
Alloy Overview
- Incoloy 800 (N08800) — The base grade. Excellent oxidation and carburization resistance up to ~870°C. General-purpose high-temperature service.
- Incoloy 800H (N08810) — Higher carbon content (0.05–0.10%) for improved creep and rupture strength at temperatures above 600°C. Grain size controlled to ASTM No. 5 or coarser.
- Incoloy 800HT (N08811) — A further refinement of 800H with a controlled Al+Ti content (≥0.85%) for optimized high-temperature strength. Best choice for the most demanding creep-limited applications above 700°C.
Chemical Composition Comparison (ASTM B408)
All values are weight percent (%). Min = minimum required; Max = maximum allowed.
Incoloy 800 — N08800
| C | Mn | Ti | S | Si | Cr | Ni | Cu | Fe | Al | |
|---|---|---|---|---|---|---|---|---|---|---|
| Min | — | — | 0.15 | — | — | 19.0 | 30.0 | — | 39.5 | 0.15 |
| Max | 0.10 | 1.5 | 0.60 | 0.015 | 1.0 | 23.0 | 35.0 | 0.75 | — | 0.60 |
Incoloy 800H — N08810
| C | Mn | Ti | S | Si | Cr | Ni | Cu | Fe | Al | |
|---|---|---|---|---|---|---|---|---|---|---|
| Min | 0.05 | — | 0.15 | — | — | 19.0 | 30.0 | — | 39.5 | 0.15 |
| Max | 0.10 | 1.5 | 0.60 | 0.015 | 1.0 | 23.0 | 35.0 | 0.75 | — | 0.60 |
Incoloy 800HT — N08811
| C | Mn | Ti | S | Si | Cr | Ni | Cu | Fe | Al | Al+Ti | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | 0.06 | — | 0.15 | — | — | 19.0 | 30.0 | — | 39.5 | 0.15 | 0.85 |
| Max | 0.10 | 1.5 | 0.60 | 0.015 | 1.0 | 23.0 | 35.0 | 0.75 | — | 0.60 | 1.20 |
Mechanical Properties Comparison (ASTM B408)
| Grade | UNS | Tensile Strength Rm (N/mm²) min | Yield Strength Rp0.2 (N/mm²) min | Elongation A (%) min |
|---|---|---|---|---|
| Incoloy 800 | N08800 | ≥515 | ≥205 | ≥30 |
| Incoloy 800H | N08810 | ≥450 | ≥170 | ≥30 |
| Incoloy 800HT | N08811 | ≥450 | ≥170 | ≥30 |
Note: 800H and 800HT have lower room-temperature tensile and yield strength minimums than 800 because their higher carbon content and controlled grain size are optimized for elevated-temperature creep strength, not room-temperature tensile performance.
Key Differences at a Glance
| Parameter | Incoloy 800 (N08800) | Incoloy 800H (N08810) | Incoloy 800HT (N08811) |
|---|---|---|---|
| Carbon range (%) | ≤0.10 | 0.05–0.10 | 0.06–0.10 |
| Al+Ti control | No combined limit | No combined limit | 0.85–1.20% (controlled) |
| Grain size requirement | Not specified | ASTM No. 5 or coarser | ASTM No. 5 or coarser |
| Tensile Strength min (N/mm²) | 515 | 450 | 450 |
| Yield Strength min (N/mm²) | 205 | 170 | 170 |
| Elongation min (%) | 30 | 30 | 30 |
| Max service temperature | ~870°C | ~980°C | >980°C |
| Creep/rupture strength | Standard | Enhanced | Best in class |
| Governing standard | ASTM B408 / N08800 | ASTM B408 / N08810 | ASTM B408 / N08811 |
Application Selection Guide
Choose Incoloy 800 (N08800) when:
- Service temperature is below 600°C and creep is not a design concern
- You need oxidation and carburization resistance in furnace components, heat exchangers, and process piping
- Cost optimization is important — 800 is the most economical of the three sub-grades
- Typical applications: industrial furnace components, chemical process equipment, heat exchanger tubing
Choose Incoloy 800H (N08810) when:
- Service temperature is between 600°C and 980°C and creep resistance is required
- Long-term stress rupture life is a design criterion
- The controlled grain size (ASTM No. 5 or coarser) is specified by the design code
- Typical applications: steam superheater tubes, reformer furnace tubes, ethylene cracking furnaces, nuclear steam generators
Choose Incoloy 800HT (N08811) when:
- Service temperature exceeds 980°C or the most demanding creep-limited conditions apply
- The Al+Ti ratio must be controlled (≥0.85%) to maximize gamma-prime precipitation strengthening
- Design codes such as ASME Section VIII or Section I require 800HT specifically
- Typical applications: high-temperature reformer tubes, pyrolysis furnace components, high-pressure steam systems
FULLERKREG Supply Capabilities
FULLERKREG supplies precision fasteners, bolting, and engineered components in Incoloy 800, 800H, and 800HT:
- Material Test Certificates (MTC) — EN 10204 3.1 / 3.2 available on request
- ASTM B408 / B163 / B407 compliance — rod, bar, and tube forms for fastener and structural applications
- Custom fastener dimensions — non-standard thread forms, head styles, and lengths
- Bulk wholesale pricing — OEM and MRO procurement with competitive lead times
- Global shipping — from our manufacturing base in China to customers worldwide
Need a quote or technical consultation for Incoloy 800, 800H, or 800HT fasteners? Contact FULLERKREG with your specification and our engineering team will respond promptly.
FULLERKREG — Precision Fasteners. Global Standards. Reliable Supply.