1.4959 alloy, also referred to as UNS N08811 or Alloy 800HT, is a high-performance iron-nickel-chromium (Fe-Ni-Cr) alloy belonging to the 800 series family. It shares the same basic composition as Alloy 800 but offers significantly higher creep rupture strength – making it the material of choice for elevated-temperature service where long-term structural integrity is critical.
As a China premium nickel alloy supplier, ZYTC Alloy supplies Alloy 800HT in a full range of mill forms, including rod, bar, plate, sheet, strip, shapes, and tubular products, all fully traceable and certified to international standards.
Product Forms & Availability – 1.4959 / Alloy 800HT (UNS N08811)Alloys 800H and 800HT are available in all standard mill forms : | Product Form | Availability |
|---|
| Rod | Available | | Bar | Available | | Plate | Available | | Sheet | Available | | Strip | Available | | Shapes | Available | | Tubular products | Pipe, tube |
For all stock availability, contact Sales.
Operating Conditions & Selection CriteriaAlloy 800HT is specified when designers require the highest creep strength in the 800 series for applications involving long-term exposure at elevated temperatures (typically above 700°C) . Service Temperature Range: Optimized for continuous operation from 700°C to 1100°C (1290°F to 2010°F) Creep-Rupture Strength: Superior to Alloy 800H due to optimized Al+Ti content (0.85-1.20%) and coarse grain structure Oxidation Resistance: Excellent up to 1100°C (2010°F); high chromium and nickel content provides protection against oxidation and combustion gases Carburization Resistance: Excellent resistance to carbon absorption — essential for petrochemical cracking furnaces Nitriding Resistance: Good resistance to nitrogen absorption in high-temperature nitriding environments Stress Corrosion Cracking: High nickel content provides immunity to chloride-induced SCC
Fabrication Guidelines| Process | Guidelines |
|---|
| Hot Working | Forge at 1010-1232°C (1850-2250°F); reheat as necessary | | Cold Forming | Good formability using standard methods; intermediate annealing may be required for severe deformation | | Machining | Similar to austenitic stainless steels; requires sharp tools and adequate coolant | | Welding | Excellent weldability using GTAW/TIG, GMAW/MIG, and resistance welding; matching filler metal recommended |
Applications of Alloy 800HTThanks to its excellent creep rupture strength, oxidation resistance, and resistance to carburization and nitriding, Alloy 800HT is widely used in high-temperature environments across multiple industries. Typical Applications Include:Furnace construction – muffles, containers, bins, and holders in heat treatment plants Chemical industry – equipment for acetic anhydride and ketone production Environmental protection equipment – high-temperature flue gas systems Automotive industry – exhaust system components and turbocharger parts Power plants – superheater and reheater tubing, steam generator components
Specialized High-Temperature Applications:Steam/hydrocarbon reformers Ethylene pyrolysis furnaces and cracking tubes Ammonia and methanol production systems Gas turbine components requiring long-term creep resistance
Chemical Composition | Chemical Composition (Weight %) | Alloy 800HT (UNS N08811) Specification |
|---|
| Nickel (Ni) | 30.0 - 35.0 | | Chromium (Cr) | 19.0 - 23.0 | | Iron (Fe) | 39.5 min. (Balance) | | Carbon (C) | 0.06 - 0.10 | | Aluminum (Al) | 0.25 - 0.60 | | Titanium (Ti) | 0.25 - 0.60 | | Aluminum + Titanium (Al+Ti) | 0.85 - 1.20 | | Manganese (Mn) | 1.5 max. | | Silicon (Si) | 1.0 max. | | Copper (Cu) | 0.75 max. | | Sulfur (S) | 0.015 max. |
| Physical Properties | Metric | Imperial |
|---|
| Density | 7.9 - 8.0 g/cm³ | 0.285 - 0.289 lb/in³ | | Melting Range | 1350 - 1400°C | 2460 - 2550°F | | Modulus of Elasticity (RT) | 200 GPa | 29.0 × 10⁶ psi | | Thermal Conductivity (RT) | 12 W/m·K | 83 BTU·in/hr·ft²·°F | | Coefficient of Expansion (30-200°C) | 16.0 µm/m·°C | 8.9 µin/in·°F |
| Mechanical Properties (Annealed) | Metric | Imperial |
|---|
| Tensile Strength (min.) | 550 MPa | 80 ksi | | Yield Strength (0.2% offset, min.) | 205 MPa | 30 ksi | | Elongation (min.) | 30% | 30% | | Hardness (Brinell) | 150-180 | 150-180 |
Heat Treatment & MicrostructureAlloy 800HT requires a specialized heat treatment to achieve its optimal high-temperature properties: | Process | Temperature | Cooling | Purpose |
|---|
| Solution Annealing | 1149-1200°C (2100-2200°F) | Water quench or forced air cool | Achieve ASTM grain size of 5 or coarser; dissolve carbides; optimize creep strength |
Delivery Lead Times (after pre-payment confirmation)| Stock Status | Delivery Time |
|---|
| Products in stock | Within 3 days | | Raw material in stock | Within 10 days | | Re-melting required | 15 – 25 days |
Contact ZYTC Alloy TodayRequest a quote for 1.4959 / Alloy 800HT (UNS N08811 / Incoloy 800HT) – Iron-Nickel-Chromium Alloy – Significantly Higher Creep Rupture Strength – Solution Heat Treated at 2100°F . Please provide: Diameter / size Product form (bar / plate / sheet / tube / pipe / rod / strip / shapes) Length or weight required Quantity Destination port Any special certification requirements
📧 Email: daisy@zytcsteel.com
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