Incoloy 800H is a nickel-iron-chromium alloy designed for high-temperature service. Its UNS designation is N08810, the German Werkstoff number is 1.4958, and the Chinese GB grade equivalent is NS112.
The short version of why it exists: standard Incoloy 800 works fine below about 600 degrees C. But once you go above that, especially in applications where the pipe is under sustained stress (pressure piping, furnace tubes, reformer outlet lines), regular 800 starts to creep. The grains slide past each other, the pipe deforms, and eventually it fails.
800H fixes this by adding a controlled carbon floor. The spec says 0.05 to 0.10 percent carbon, which sounds like a small number but is actually the entire point of the grade. That carbon, combined with a high-temperature solution anneal at around 1150 degrees C, produces a coarse grain structure (ASTM 5 or coarser). Coarse grains mean fewer grain boundaries per unit volume, which means less creep. The result: roughly double the creep-rupture life of standard 800 at 700 degrees C.
There is also 800HT (UNS N08811), which adds higher aluminum plus titanium content for precipitation strengthening. 800HT costs maybe 10 to 15 percent more than 800H and is appropriate when you are running above 900 degrees C. But in most oil and gas, petrochemical, and power generation applications in the Middle East, 800H is the sweet spot. I will cover the selection criteria in more detail later.
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Where 800H Pipe Actually Gets Used
Most supplier websites will give you a bullet list: "chemical processing, power plants, heat exchangers." That does not tell you much. Here is what these applications actually look like on the ground.
Ethylene cracking furnaces. This is the biggest consumer of 800H pipe by volume. In a cracker, hydrocarbon feedstock gets heated to 800 to 850 degrees C inside radiant coils. The pipe wall sees that temperature plus internal pressure plus a carburizing atmosphere. Standard stainless grades carburize and embrittle within a few years.
800H resists carbon pickup because of its high nickel content (30 to 35 percent), and the coarse grain structure handles the creep stress from sustained operation. Saudi Arabia alone has multiple world-scale crackers: SABIC's facilities in Jubail and Yanbu, the SATORP refinery, Petro Rabigh. Every turnaround cycle, they are buying replacement furnace tubes.
Steam methane reformers. In hydrogen production and ammonia plants, reformer outlet pigtails and transfer lines run at 750 to 900 degrees C. These are smaller-diameter pipes (typically 1 to 4 inches) but the stress is high and the hydrogen partial pressure accelerates embrittlement in the wrong material. 800H is the standard spec for these components across most Middle Eastern fertilizer and refinery complexes.
Heat exchangers in high-temperature service. When you have tube-side temperatures exceeding 600 degrees C and shell-side exposure to flue gas or process gas, 800H tubes outperform 304H and 316H stainless on both oxidation resistance and creep life. Common in refinery fired heaters and waste heat recovery units.
Nuclear applications. Incoloy 800H (and its sibling 800) has a long history in nuclear steam generator tubing, particularly in CANDU and some PWR designs. The alloy resists chloride stress corrosion cracking in the secondary loop water chemistry, which is what killed a lot of 304 stainless tubing back in the 1970s. This is more of a European and North American market, but worth knowing if you are bidding on nuclear-grade material.
Power plant superheater and reheater tubing. Coal-fired and gas-fired plants in the GCC run superheater outlet temperatures that can push 800H into its useful range. The Middle East power sector is a smaller but consistent consumer.
800 vs 800H vs 800HT: When to Pick Which
This is the question I get asked most often by procurement people who have been handed a spec sheet and told "get a quote." Here is a decision framework that is simpler than comparing creep curves.
| Grade | UNS | Carbon | Grain Size | Continuous Service Limit | Relative Cost | When to Use |
|---|---|---|---|---|---|---|
| 800 | N08800 | ≤0.10 (no minimum) | Not specified | ~600°C | Baseline | Heat exchanger tubing below 600°C; nitric acid service; non-structural furnace parts |
| 800H | N08810 | 0.05–0.10 | ASTM 5 or coarser | ~900°C | +8 to 15% over 800 | Reformer outlet lines; cracking furnace radiant coils; any pressure piping above 600°C |
| 800HT | N08811 | 0.06–0.10; Al+Ti ≥0.85% | ASTM 5 or coarser | ~980°C | +15 to 25% over 800 | Ethylene furnace radiant tubes; applications above 900°C where every hour of creep life counts |
Chemical Composition (ASTM B407 / ASME SB407)
| Element | 800H (N08810) Requirement |
|---|---|
| Nickel (Ni) | 30.0 – 35.0% |
| Chromium (Cr) | 19.0 – 23.0% |
| Iron (Fe) | ≥ 39.5% (balance) |
| Carbon (C) | 0.05 – 0.10% |
| Aluminum (Al) | 0.15 – 0.60% |
| Titanium (Ti) | 0.15 – 0.60% |
| Manganese (Mn) | ≤ 1.50% |
| Silicon (Si) | ≤ 1.00% |
| Sulfur (S) | ≤ 0.015% |
| Phosphorus (P) | ≤ 0.030% |
| Copper (Cu) | ≤ 0.75% |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength (min) | 520 MPa (75,000 psi) |
| Yield Strength, 0.2% offset (min) | 205 MPa (30,000 psi) |
| Elongation (min) | 30% |
| Density | ~7.94 g/cm³ |
| Melting Range | 1350 – 1400°C |
Standards and Certifications that Matter for Middle East Projects
If you are supplying to Aramco, ADNOC, SABIC, QP, KNPC, or any GCC national oil company, the material specification is only half the battle. The documentation is the other half. Here is what actually matters.
The Standards Stack
For seamless 800H pipe, the primary standard is ASTM B407 (or ASME SB407 for pressure vessel applications). For welded pipe, it is ASTM B514. Most Middle East projects specify B407 seamless.
Pipe dimensions follow ASME B36.10M (for welded and seamless wrought steel pipe) or ASME B36.19M (stainless steel pipe). If your order is in metric, confirm whether the mill is supplying OD per B36.19M or a true metric OD.
Material Test Certificates (MTC)
Aramco's standard purchase order terms almost always require an EN 10204 Type 3.1 inspection certificate at minimum. This means the manufacturer certifies that the material meets the order specification, and the certification is signed by a quality representative independent of the production department. For critical service (lethal service, high-pressure steam, hydrogen), the spec may require Type 3.2, which adds third-party inspection by an authorized inspector (typically SGS, TUV, Bureau Veritas, or a nominated Aramco inspector).
The MTC must show:
- Heat number and traceability to the original melt
- Full chemical composition (not just "conforms to ASTM B407")
- Mechanical test results (tensile, yield, elongation) for the specific heat
- Hydrostatic test or eddy current test results if specified
- Heat treatment condition and temperature
- Grain size determination (this matters for 800H: if the grain size is not reported, you cannot verify it is actually 800H rather than 800 dressed up with a different certificate)
Frequently Asked Questions
Q: What is the difference between Incoloy 800H and Incoloy 825?
800H (N08810) is designed for high-temperature strength and creep resistance. It has about 30 to 35 percent nickel, 19 to 23 percent chromium, and the balance is iron. 825 (N08825) adds molybdenum and copper for resistance to reducing acids and chloride pitting. It is used in chemical processing and seawater applications, not in furnace or reformer service. If your application involves sulfuric acid or seawater, you want 825. If it involves temperatures above 600 degrees C under pressure, you want 800H.
Q: Can 800H pipe be welded to carbon steel?
Yes, but it requires a qualified welding procedure. The typical filler metal is Inconel 182 (for SMAW) or ERNiCr-3 (for GTAW). Post-weld heat treatment is not normally required for 800H unless the service environment raises stress corrosion cracking risk. The main concern is differential thermal expansion: 800H expands about 30 percent more than carbon steel at operating temperature. Pipe supports and expansion loops need to accommodate this.
Q: How do I verify the pipe is actually 800H and not standard 800?
Check the MTC for carbon content (must be 0.05 to 0.10 percent) and grain size (ASTM 5 or coarser). If neither is reported, the material is suspect. For high-value or critical orders, request third-party PMI plus carbon analysis on a sample. A portable OES (optical emission spectroscopy) unit can verify carbon content non-destructively. PMI with XRF alone is not sufficient because XRF does not measure carbon reliably.
Q: What is the lead time for custom 800H pipe sizes?
Mill production runs for non-stock sizes typically take 8 to 16 weeks from order confirmation to ex-works readiness. Add 3 to 5 weeks for ocean freight to the Middle East. Total lead time: roughly 12 to 20 weeks. Stock sizes ship in 1 to 3 weeks from major stockists. If your project timeline is tight, pay the stockist premium rather than waiting for a mill run.
Q: Does 800H pipe require any special storage or handling?
Not particularly. It does not rust, so indoor storage is nice but not mandatory. The main thing: keep the heat number markings legible. If the markings get rubbed off during transport or storage, you lose traceability, and the MTC becomes useless. We recommend steel-stamped markings rather than paint or ink for material that may sit in an outdoor yard for months.
Q: What is the HS code for Incoloy 800H pipe?
Nickel alloy seamless pipe typically falls under HS code 7304.41 (cold-drawn or cold-rolled) or 7304.49 (other seamless pipe of stainless or alloy steel). Confirm with your customs broker, as classification can vary by country and by whether the pipe is classified under stainless steel or nickel alloy based on the predominant element.
Get a Quote for Incoloy 800H Pipe
If you are sourcing 800H pipe for a project and want a price that accounts for the actual specification, quantity, delivery port, and certification requirements, send us your RFQ. We quote within one working day and provide a formal proforma invoice with full Incoterms, delivery schedule, and documentation scope.
