Project Description
Incoloy 028 (UNS N08028 / W. Nr. 1.4563 / X1NiCrMoCu31-27-4) is a nickel-iron-chromium austenitic alloy with precise additions of molybdenum (3.0–4.0 %), copper (0.6–1.4 %), and an ultra-low carbon ceiling of 0.030 % max. This composition was purpose-engineered to resist corrosion in sulfuric acid across a wide range of concentrations and temperatures, while the high chromium level (26–28 %) simultaneously delivers strong resistance to oxidizing media, pitting, crevice corrosion, and SCC in chloride environments. With nickel at 30–34 %, the alloy is immune to chloride-induced stress corrosion cracking that limits conventional austenitic stainless steels, and it is listed in NACE MR0175 / ISO 15156-3 for sour (H₂S) service. In oil and gas, Incoloy 028 bar is selected for deep sour gas well components, HDS reactor internals, offshore process piping, and FGD scrubber parts where both chloride and sulfuric acid attack must be managed simultaneously. SHUNFU METAL supplies N08028 bar from VIM-cast, solution-annealed heats, ultrasonically tested per ASTM E114, with EN 10204 3.1 / 3.2 MTR on every shipment.
Incoloy 028 / N08028 — Introduction
Alloy 028 occupies a unique niche between standard austenitic stainless steels (e.g. 904L / N08904) and the more expensive nickel-base alloys (e.g. Incoloy 825 / Alloy 625). It achieves this by combining higher chromium (26–28 %) and molybdenum (3.0–4.0 %) than 904L with a well-balanced nickel/copper matrix that specifically targets sulfuric and phosphoric acid resistance. The PREN (Cr + 3.3×Mo + 16×N) typically exceeds 38, providing meaningful pitting resistance in seawater and chloride brine environments encountered on offshore platforms and in coastal refineries. The ultra-low carbon content (≤ 0.030 %) minimizes sensitization risk and eliminates the need for post-weld solution annealing in most fabrication scenarios.
SHUNFU METAL hot-forges or hot-rolls N08028 billets and applies a full solution anneal at 1,100–1,150 °C (water quench or rapid cool) to dissolve any precipitates and restore maximum corrosion resistance. Each bar is 100 % ultrasonically tested per ASTM E114, and grain-boundary corrosion screening per ASTM G28 or ASTM A262 Practice B is available on request. Hardness is verified at ≤ 35 HRC (≤ 321 HBW) for NACE MR0175 compliance. Chemical composition is certified by OES and independently verified by SGS, Bureau Veritas, or TÜV upon customer request.
Equivalent Grades & Applicable Standards
| Standard Body | Designation | Applicable Specification / Form |
|---|---|---|
| ASTM / ASME | UNS N08028 | B805 / SB-805 (bar), B709 (plate/sheet/strip), B668 / SB-668 (seamless pipe & tube), B690 (welded tube), B366 (fittings), B564 / SB-564 (forgings) |
| EN / DIN | 1.4563 / X1NiCrMoCu31-27-4 | EN 10028-7 (pressure vessels), EN 10088-3 (bar & shapes), DIN 2.4603 (DIN designation for tube/pipe), DIN 17744 (bar) |
| ISO | NW 8028 | ISO 9723 (bar & wire), ISO 15156-3 (NACE sour service) |
| AFNOR (France) | Z1NCDU31-27-03 | NF A35-574 |
| GB (China) | NS3304 | GB/T 15007 (wrought nickel alloy designation) |
| NACE / PED | NACE MR0175 / ISO 15156-3 | Approved for sour-service (H₂S) environments; PED 2014/68/EU certified for pressure equipment |
Oil & Gas Applications — N08028 Bar Components
- Downhole tubing & completion strings
- Packer mandrels (high H₂S wells)
- Wellbore seal assemblies
- Wire-line tool bar bodies
- Downhole valve stems & plugs
- Wellhead valve bodies & bonnets
- Gate valve seats & stems
- Choke body & bean holders
- Christmas tree spool bars
- High-pressure flange studs
- Subsea manifold bar components
- Seawater pump shafts & sleeves
- Offshore platform heat exchanger bars
- Riser clamp tie-rod bars
- Mooring chain guide bars
- HDS reactor distributor bars
- Amine regenerator internals
- Sour-water stripper components
- Sulfuric acid alkylation unit parts
- Spent acid handling valve bars
- FGD absorber agitator shafts
- Stack scrubber spray nozzle bars
- Electrostatic precipitator hangers
- Waste-acid neutralization vessel bars
- Offshore flare stack internal bars
- Sour gas pipeline pig-receiver bars
- Sulfuric acid process piping flanges
- Phosphoric acid evaporator shafts
- Acid service pump impeller bars
- H₂SO₄ concentration unit internals
Supply — Bar Sizes & Forms (Incoloy 028 / N08028)
| Form | Size Range | Standard / Process | Length |
|---|---|---|---|
| Hot-Rolled Round Bar | Ø 8 – Ø 200 mm | ASTM B805 / EN 10088-3 | 2,000 – 6,000 mm |
| Cold-Drawn Round Bar | Ø 6 – Ø 80 mm | ASTM B805 (cold-drawn) | 1,000 – 4,000 mm |
| Hot-Rolled Flat Bar | T 6–120 × W 20–400 mm | ASTM B805 / EN 10088-3 | 2,000 – 6,000 mm |
| Forged Round Bar | Ø 80 – Ø 850 mm | ASTM B564 / EN 10243 | 500 – 3,500 mm |
| Forged Flat Bar / Slab | T 30–300 × W 50–750 mm | ASTM B564 / EN 10243 | 500 – 3,000 mm |
| Hexagonal Bar | Across-flat 8 – 100 mm | ASTM B805 | 1,000 – 4,000 mm |
All stock is solution-annealed at 1,100–1,150 °C, water-quenched. Surface: black (as-forged/rolled), turned, or centreless-ground. Tolerances per ASTM B805 or customer specification. NACE MR0175 hardness compliance (≤ 35 HRC / 321 HBW) certified on request. SHUNFU METAL maintains stock in Ø 20–150 mm round bar for prompt delivery; non-standard sizes available within 2–4 weeks from dedicated forge and rolling lines.
Chemical Composition — Incoloy 028 / N08028 (ASTM B805 / EN 1.4563)
| Element | Ni | Cr | Fe | Mo | Cu | Mn | Si | C | P | S |
|---|---|---|---|---|---|---|---|---|---|---|
| Min (%) | 30.0 | 26.0 | bal. | 3.0 | 0.6 | — | — | — | — | — |
| Max (%) | 34.0 | 28.0 | bal. | 4.0 | 1.4 | 2.5 | 1.0 | 0.030 | 0.030 | 0.030 |
Source: ASTM B805 / EN 10088-3 (1.4563). Key differentiators versus 904L (N08904): Molybdenum raised to 3.0–4.0 % (vs. 4.0–5.0 % in 904L), but significantly higher chromium (26–28 % vs. 19–23 %) and the same ultra-low carbon (≤ 0.030 %) providing comparable pitting index with superior oxidizing acid resistance. SHUNFU METAL performs full OES + IGF sulfur/carbon analysis on every heat, with chemistry certificate traceable to heat number and cast.
Mechanical Properties — Incoloy 028 Bar (ASTM B805 / EN 10088-3)
| Form / Condition | UTS (MPa) | 0.2% YS (MPa) | Elongation (%) | Hardness |
|---|---|---|---|---|
| Bar / Annealed (min. per ASTM B805) | 690 min. | 310 min. | 40 min. | 200 HB max. |
| Bar / Annealed (typical) | 620–750 | 300–400 | 35–50 | 170–220 HB |
| Bar / Hot-Finished (typical) | 640–720 | 280–370 | 38–48 | 160–205 HB |
| Bar / Cold-Drawn (typical) | 750–900 | 500–650 | 20–35 | 220–280 HB |
| Forgings / Annealed (typical) | 620–720 | 310–390 | 35–45 | 170–215 HB |
| ASME Design Allowable (38–100 °C) | — | 138 MPa max. | — | ≤ 35 HRC (NACE) |
Heat treatment: solution anneal at 1,100–1,150 °C, water quench. NACE MR0175 / ISO 15156-3 sour-service compliance requires hardness ≤ 35 HRC (321 HBW). SHUNFU METAL performs tensile testing per ASTM E8, Brinell hardness per ASTM E10, and corrosion screening per ASTM G28 Method A (boiling 50 % H₂SO₄ + Fe₂(SO₄)₃) on sour-service orders. Charpy V-notch impact testing per ASTM E23 and CTOD fracture toughness available for subsea and low-temperature applications.