ASTM B366 is the specification for factory-made wrought nickel and nickel alloy buttweld fittings. It covers fittings made from Inconel, Monel, Hastelloy, Incoloy, and other nickel-based alloys, used in severely corrosive and high-temperature environments where stainless and duplex steels are insufficient. Dimensions follow ASME B16.9.
| Property | Detail |
|---|
| Specification | ASTM B366 |
| Full title | Standard Specification for Factory-Made Wrought Nickel and Nickel Alloy Fittings |
| Fitting types | Elbows, tees, reducers, caps, stub ends (per ASME B16.9) |
| Size range | NPS 1/2 to NPS 24 (larger sizes available) |
| Wall schedules | 5S, 10S, 40S, 80S, and heavier |
| End preparation | Butt weld bevel per ASME B16.25 |
Common ASTM B366 Grades
| B366 Grade | UNS | Trade Name | Key Alloying | Primary Resistance |
|---|
| WP N06600 | N06600 | Inconel 600 | 72Ni-15Cr-8Fe | High-temp oxidation, carburization |
| WP N06625 | N06625 | Inconel 625 | 60Ni-22Cr-9Mo | Seawater, acids, high temperature |
| WP N08825 | N08825 | Incoloy 825 | 42Ni-21Cr-3Mo | Sulfuric/phosphoric acid, SCC |
| WP N10276 | N10276 | Hastelloy C-276 | 57Ni-16Cr-16Mo | Universal acid resistance |
| WP N04400 | N04400 | Monel 400 | 67Ni-30Cu | Hydrofluoric acid, seawater |
| WP N08810 | N08810 | Incoloy 800H | 32Ni-21Cr-46Fe | High-temp (800+ degrees C) |
| WP N06022 | N06022 | Hastelloy C-22 | 56Ni-22Cr-13Mo | Aggressive mixed-acid environments |
Mechanical Properties (Selected Grades)
| Property | N06625 (Inconel 625) | N10276 (Hastelloy C-276) | N04400 (Monel 400) |
|---|
| Min yield | 414 MPa | 283 MPa | 172 MPa |
| Min tensile | 827 MPa | 690 MPa | 483 MPa |
| Elongation | 30% | 40% | 35% |
Applications by Industry
| Industry | Common B366 Grades | Service |
|---|
| Offshore oil and gas | N06625, N08825 | Sour gas, seawater, downhole |
| Chemical processing | N10276, N06022 | Acids, chlorides, mixed chemicals |
| Power generation | N06600, N08810 | Steam generators, superheaters |
| Pulp and paper | N10276 | Bleach plant, chlorine dioxide |
| Pharmaceutical | N06625, N10276 | Ultra-pure processing |
| Flue gas desulfurization | N06625, N10276 | Wet scrubber environments |
ASTM B366 vs A403 (Stainless Steel)
| Feature | B366 (Nickel Alloys) | A403 (Stainless Steel) |
|---|
| Nickel content | 30-72% | 8-14% |
| Corrosion resistance | Superior | Good |
| Max service temperature | Up to 1100 degrees C (grade dependent) | Up to 800 degrees C |
| Chloride SCC resistance | Excellent | Limited (austenitic grades) |
| Cost | 5-20x carbon steel | 2-5x carbon steel |
| Availability | Limited stock, long lead times | Widely stocked |
Procurement and Testing
Nickel alloy fittings are high-value items requiring careful procurement:
| Aspect | Requirement |
|---|
| Material certificate | EN 10204 Type 3.1 mandatory |
| PMI (Positive Material ID) | Required per most project specs |
| Intergranular corrosion test | ASTM G28 (Method A) for Hastelloy; ASTM A262 for Incoloy |
| Solution annealing | Mandatory (temperature varies by grade) |
| Lead time | 12-24 weeks for most grades |
| Stocked grades | N06625 and N08825 in limited sizes |
For matching pipe specifications, see the nickel alloy pipe materials guide.
Read the full guide to pipe fittings
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