Q1: What does ASTM B409 cover for UNS N08810 plate, and how does it differ from ASTM B409 for UNS N08800?
A: ASTM B409 is the standard specification for nickel-iron-chromium alloy plate, sheet, and strip. It covers three UNS designations: N08800 (standard Incoloy 800), N08810 (Incoloy 800H), and N08811 (Incoloy 800HT). For UNS N08810 specifically, the standard defines chemistry, mechanical properties, and manufacturing requirements optimized for high-temperature creep service.
Key Differences – N08810 vs. N08800 under ASTM B409:
| Parameter | UNS N08800 (Standard) | UNS N08810 (800H) |
|---|---|---|
| Carbon (C) | 0.10% max | 0.05-0.10% (controlled minimum) |
| Aluminum (Al) | 0.15-0.60% | 0.15-0.60% |
| Titanium (Ti) | 0.15-0.60% | 0.15-0.60% |
| Al+Ti total | 0.30-1.20% | 0.30-1.20% |
| Grain size requirement | Not specified | ASTM 5 or coarser |
| Primary application | General corrosion resistance | High-temperature creep service |
Why the Carbon Minimum Matters for N08810:
The controlled carbon range (0.05-0.10%) in UNS N08810 promotes the formation of fine chromium carbide precipitates at grain boundaries. These carbides pin the grain structure, preventing grain boundary sliding at elevated temperatures. This mechanism dramatically improves creep-rupture strength above 600°C (1112°F).
Below 0.05% carbon: Insufficient carbide formation; material behaves like N08800 with poor creep resistance
0.05-0.10% carbon: Optimal carbide distribution; maximum creep strength
Above 0.10% carbon: Excessive carbides may form continuous grain boundary network (brittleness)
Grain Size Requirement (ASTM 5 or Coarser):
ASTM B409 for N08810 requires verification of grain size per ASTM E112. Coarser grains (ASTM 5 vs. finer grains like ASTM 8) reduce grain boundary area, which in turn:
Reduces grain boundary sliding (improves creep resistance)
Reduces sites for carbide precipitation (prevents over-sensitization)
Improves oxidation resistance at very high temperatures
ASTM B409 Plate – Available Sizes and Tolerances:
| Parameter | Range | Tolerance |
|---|---|---|
| Thickness | 3.0 mm to 75 mm (1/8" to 3") | ±0.3 mm for <5 mm; ±10% for thicker |
| Width | Up to 2500 mm (100") | ±3 mm |
| Length | Up to 12000 mm (40 ft) | ±5 mm |
| Flatness | Per ASTM A480 | ≤5 mm per meter |
Specifying Correctly:
"Plate, Incoloy 800H (UNS N08810), ASTM B409, 10 mm thick × 2000 mm wide × 6000 mm long, solution annealed, pickled. Grain size ASTM 5 or coarser per ASTM E112. Mill Test Reports per EN 10204 Type 3.1."
Summary: ASTM B409 UNS N08810 plate is distinguished from N08800 by its controlled carbon range (0.05-0.10% minimum) and coarser grain size requirement (ASTM 5 or coarser). These features optimize the material for high-temperature creep service above 600°C, making it the preferred choice for furnace components, heat exchangers, and petrochemical process equipment.
Q2: What are the key mechanical properties and heat treatment requirements for ASTM B409 UNS N08810 plate?
A: ASTM B409 specifies minimum mechanical properties for UNS N08810 plate in the solution annealed condition. Proper heat treatment is essential to develop the microstructure required for high-temperature service.
Mechanical Property Requirements (Room Temperature):
| Property | ASTM B409 Requirement (UNS N08810) | Typical Achieved Value |
|---|---|---|
| Tensile strength (min) | 450 MPa (65 ksi) | 550-650 MPa |
| Yield strength 0.2% offset (min) | 170 MPa (25 ksi) | 200-280 MPa |
| Elongation in 50 mm (min) | 30% | 35-45% |
| Hardness (typical, not specified) | - | 140-200 HB / 75-90 HRB |
Elevated Temperature Mechanical Properties (Informational, for Design):
| Temperature | Tensile Strength (typical) | Yield Strength (typical) | Creep Strength (1% in 10,000h, typical) |
|---|---|---|---|
| 400°C (750°F) | 480-580 MPa | 150-220 MPa | ~120 MPa |
| 500°C (930°F) | 450-550 MPa | 140-200 MPa | ~80 MPa |
| 600°C (1110°F) | 400-500 MPa | 130-180 MPa | ~45 MPa |
| 700°C (1290°F) | 300-400 MPa | 100-140 MPa | ~25 MPa |
| 800°C (1470°F) | 200-280 MPa | 70-90 MPa | ~12 MPa |
Heat Treatment Requirements (ASTM B409):
| Parameter | Requirement | Why |
|---|---|---|
| Solution annealing temperature | 1150-1200°C (2100-2190°F) | Dissolves carbides, sets grain size |
| Cooling method | Rapid cooling (water quench for thick sections; air cool for thin) | Prevents carbide precipitation during cooling |
| Atmosphere | Controlled (air for pickled finish; inert for bright finish) | Prevents excessive scaling |
Verification of Proper Heat Treatment:
| Test | Method | Acceptance |
|---|---|---|
| Grain size | ASTM E112 | ASTM 5 or coarser |
| Hardness | Rockwell B or Brinell | 75-90 HRB (140-190 HB) typical |
| Intergranular corrosion (optional) | ASTM G28 | Corrosion rate <12 mm/year |
Effect of Improper Heat Treatment:
| Condition | Problem | Consequence |
|---|---|---|
| Annealing temperature too low (<1150°C) | Carbides not fully dissolved | Reduced creep strength, potential sensitization |
| Annealing temperature too high (>1200°C) | Excessive grain growth (ASTM 0 or coarser) | Reduced ductility, low tensile strength |
| Cooling too slow (furnace cool) | Carbide precipitation during cooling | Reduced corrosion resistance (sensitized) |
| No solution anneal (as-rolled) | Cold worked structure | Low ductility, unpredictable creep performance |
Summary: ASTM B409 UNS N08810 plate must be solution annealed at 1150-1200°C and rapidly cooled to achieve the coarser grain size (ASTM 5 or coarser) and carbide distribution required for high-temperature creep resistance. Mechanical properties at room temperature are similar to N08800, but elevated temperature performance is significantly superior.
Q3: What are the primary applications for ASTM B409 UNS N08810 plate in high-temperature industries?
A: UNS N08810 plate is specified for equipment operating in the 600-815°C (1112-1500°F) range where creep strength, oxidation resistance, and structural stability are required. The plate form is used for furnace linings, heat exchanger shells, pressure vessels, and process equipment.
Primary Industries and Applications:
1. Petrochemical Processing (Steam Methane Reforming)
| Component | Operating Temperature | Why N08810 Plate |
|---|---|---|
| Reformer furnace linings (walls and roofs) | 800-950°C (internal) | Oxidation resistance, creep strength |
| Transfer line manifolds | 750-850°C | Creep resistance, weldability |
| Air preheater shells | 600-700°C | Thermal fatigue resistance |
| Waste heat boiler shells | 500-650°C | Corrosion resistance to flue gases |
2. Heat Treating and Metal Processing
| Component | Operating Temperature | Why N08810 Plate |
|---|---|---|
| Radiant tube furnace shells | 700-900°C | Oxidation resistance, structural stability |
| Muffle furnace liners | 600-800°C | Carburization resistance, creep strength |
| Retort shells (vacuum furnaces) | 500-700°C (cyclic) | Thermal fatigue resistance |
| Roller hearth furnace liners | 600-750°C | Dimensional stability |
3. Power Generation
| Component | Operating Temperature | Why N08810 Plate |
|---|---|---|
| Superheater header shells | 550-650°C | Creep strength, fireside corrosion |
| HRSG interstage ducting | 500-600°C | Thermal fatigue, weldability |
| Concentrated solar power (CSP) receiver panels | 500-600°C | Molten salt corrosion resistance |
4. Chemical Processing (High Temperature)
| Component | Operating Temperature | Why N08810 Plate |
|---|---|---|
| Nitric acid plant high-temperature absorbers | 80-200°C (not high temp) | Actually N08800 is used; N08810 overkill |
| Phosphoric acid evaporator shells | 100-150°C | Not high temp; N08800 sufficient |
| Sulfur recovery unit (Claus process) reaction chambers | 500-600°C | H₂S + SO₂ resistance |
Plate Thickness Selection Guide:
| Application | Typical Thickness | Why |
|---|---|---|
| Furnace liners (single-wall) | 3-6 mm (1/8-1/4") | Light gauge reduces thermal mass and cost |
| Pressure vessel shells | 10-25 mm (3/8-1") | Pressure containment + creep allowance |
| Heat exchanger shells | 8-15 mm (5/16-5/8") | Pressure + corrosion allowance |
| Ducting and breeching | 4-8 mm (5/32-5/16") | Structural + oxidation allowance |
Design Advantages of N08810 Plate:
| Advantage | Explanation |
|---|---|
| Higher allowable stress at 700°C | ASME Section VIII Division 1 allows ~25 MPa for N08810 vs. ~15 MPa for N08800 |
| Longer creep life | 2-3x longer time to 1% creep at 650°C compared to N08800 |
| Oxidation resistance to 815°C | Continuous service without significant scaling |
| Resistance to carburization | Important in hydrocarbon and CO-rich atmospheres |
| Weldability | Readily welded using standard techniques (ERNiCr-3 filler) |
Limitations – When N08810 is NOT Recommended:
| Condition | Better Choice |
|---|---|
| Continuous temperature >815°C (1500°F) | Incoloy 800HT (N08811) or Inconel 601 |
| Severe carburization (high carbon activity, >900°C) | Inconel 601 or 693 |
| High-pressure hydrogen (>100 bar, >400°C) | Seamless pipe (not plate) or Inconel 625 |
| Seawater or high-chloride immersion (low temperature) | Incoloy 825 or super duplex |
Summary: ASTM B409 UNS N08810 plate is the standard material for high-temperature equipment operating at 600-815°C in petrochemical, heat treating, and power generation industries. Its combination of creep strength, oxidation resistance, and fabricability makes it the preferred choice over N08800 for sustained high-temperature service.
Q4: How does UNS N08810 plate compare to UNS N08800 and N08811 plates for high-temperature applications?
A: Selecting the correct grade of Incoloy plate requires understanding the temperature-dependent performance differences among N08800, N08810, and N08811. Each grade is optimized for a specific temperature range and service condition.
Grade Comparison Summary:
| Property | N08800 (Standard) | N08810 (800H) | N08811 (800HT) |
|---|---|---|---|
| Carbon (C) | 0.10% max | 0.05-0.10% | 0.06-0.10% |
| Aluminum (Al) | 0.15-0.60% | 0.15-0.60% | 0.25-0.60% |
| Titanium (Ti) | 0.15-0.60% | 0.15-0.60% | 0.25-0.60% |
| Al+Ti total | 0.30-1.20% | 0.30-1.20% | 0.85-1.20% |
| Grain size requirement | Not specified | ASTM 5 or coarser | ASTM 5 or coarser |
| Maximum continuous temperature | 600°C (1112°F) | 815°C (1500°F) | 980°C (1800°F) |
| Creep strength (relative at 700°C) | Low (1x baseline) | High (3-4x N08800) | Very high (5-6x N08800) |
| Thermal fatigue resistance | Excellent | Good | Moderate |
| Weldability | Excellent | Good | Fair (PWHT often required) |
| Cost (relative) | 1.0x | 1.2-1.3x | 1.4-1.6x |
Application-Based Selection Guide:
| Operating Temperature | Recommended Grade | Why |
|---|---|---|
| Below 540°C (1000°F) | N08800 (Standard) | Sufficient; lowest cost |
| 540-650°C (1000-1200°F) | N08810 (800H) | Creep becomes significant; 800H required |
| 650-815°C (1200-1500°F) | N08810 (800H) | Standard choice for most high-temperature equipment |
| 815-980°C (1500-1800°F) | N08811 (800HT) | Maximum creep strength; limited thermal cycling |
| Cyclic service (frequent startup/shutdown) | N08800 or N08810 (not 800HT) | 800HT has lower thermal fatigue resistance |
Creep Strength Comparison (Stress to Produce 1% Creep in 10,000 hours):
| Temperature | N08800 (MPa) | N08810 (MPa) | N08811 (MPa) |
|---|---|---|---|
| 600°C | ~30 | ~45 | ~50 |
| 650°C | ~15 | ~30 | ~35 |
| 700°C | ~8 | ~18 | ~25 |
| 750°C | ~4 | ~10 | ~15 |
| 800°C | ~2 | ~5 | ~8 |
Oxidation Resistance Comparison (Weight gain after 1000 hours in air):
| Temperature | N08800 (mg/cm²) | N08810 (mg/cm²) | N08811 (mg/cm²) |
|---|---|---|---|
| 600°C | ~3 | ~3 | ~2 |
| 700°C | ~8 | ~7 | ~5 |
| 800°C | ~20 | ~18 | ~12 |
| 900°C | Not rated | ~50 | ~30 |
Thermal Fatigue Resistance:
| Grade | Relative Thermal Fatigue Life (Cycles to Failure at ΔT=500°C) |
|---|---|
| N08800 | Best (baseline) |
| N08810 | Good (70-80% of N08800) |
| N08811 | Moderate (40-50% of N08800) |
Why N08811 has Lower Thermal Fatigue Resistance: The higher Al+Ti content (0.85-1.20%) promotes gamma prime (γ′) precipitation, which strengthens the alloy at high temperatures but also reduces ductility and increases susceptibility to thermal cycling damage.
Practical Recommendation:
| Scenario | Selection |
|---|---|
| New furnace, steady-state operation at 750°C | N08810 (best balance) |
| Existing furnace upgrade, need higher throughput (temperature) | N08811 (if 800-850°C) |
| Batch furnace, frequent door openings (thermal cycling) | N08810 (not 800HT) |
| Cost-sensitive project, operating at 550°C | N08800 |
| Maximum possible creep life at 850°C | N08811 |
Summary: For plate applications in the 600-815°C range, ASTM B409 UNS N08810 (800H) is the standard and most versatile choice. N08800 is limited to below 600°C. N08811 (800HT) is reserved for service above 815°C or where maximum creep strength is required, but it has lower thermal fatigue resistance and is more expensive.
Q5: How should ASTM B409 UNS N08810 plate be fabricated, welded, and inspected for high-temperature service?
A: Proper fabrication, welding, and inspection of UNS N08810 plate are essential to preserve the high-temperature creep strength and corrosion resistance of the material. Improper practices can create weld zones that fail prematurely in service.
Fabrication Guidelines:
| Operation | Recommendation | Why |
|---|---|---|
| Cutting (shearing, plasma, laser) | Use clean, sharp tools; remove HAZ (heat-affected zone) after plasma/laser cutting | Prevents cracking initiation from rough edges |
| Forming (cold) | Use larger bend radii (≥2× plate thickness for 90° bends) | N08810 has moderate ductility; tight bends may crack |
| Forming (hot) | Heat to 950-1050°C, form, then solution anneal | Hot forming without post-anneal may leave residual stresses |
| Machining | Use sharp carbide tools, positive rake, coolant flood | Work hardens rapidly; dull tools cause galling |
Welding Guidelines:
| Parameter | Recommendation |
|---|---|
| Process | GTAW (TIG) or SMAW (stick) – preferred; GMAW (MIG) – acceptable |
| Filler metal | ERNiCr-3 (Inconel 82) – standard; ERNiFeCr-1 (Incoloy 800 filler) – also acceptable |
| Shielding gas | 100% Argon (GTAW); Argon + 2-5% Hydrogen for root pass (optional) |
| Back purge | Required for full-penetration welds (argon on back side) |
| Interpass temperature | ≤150°C (300°F) – do not overheat |
| Heat input | 10-20 kJ/in (low to moderate) |
| Post-weld heat treatment (PWHT) | Not required for N08810 (but may be specified for thick sections or code applications) |
Special Consideration for N08810 vs. N08800 Welding:
| Grade | PWHT Requirement | Reason |
|---|---|---|
| N08800 | Not required | Standard solution annealed structure |
| N08810 | Not normally required | But if PWHT is performed, use 980°C + rapid cool |
| N08811 | Often required (980°C + quench) | To restore creep properties in weld HAZ |
Weld Preparation:
| Step | Detail |
|---|---|
| Cleaning | Remove oil, grease, and surface contaminants (acetone or alcohol) |
| Bevel | Single V or double V depending on thickness; 60-70° included angle |
| Root gap | 2-4 mm (0.08-0.16") |
| Land (root face) | 1-2 mm (0.04-0.08") |
Inspection and Testing:
| Test | Method | Acceptance | Frequency |
|---|---|---|---|
| Visual inspection | Naked eye or 2x magnification | No cracks, undercut, porosity | 100% of welds |
| Dye penetrant (PT) | ASTM E165 | No linear indications | 100% of critical welds |
| Radiographic (RT) | ASTM E94 | No cracks, lack of fusion | Spot or 100% per code |
| Ultrasonic (UT) | ASTM E213 | No indications >1.2 mm | Thick sections (>12 mm) |
| Hardness traverse (across weld) | ASTM E18 | ≤95 HRB (≤200 HB) | Sour service or code requirement |
Post-Fabrication Cleaning and Passivation:
| Step | Method | Why |
|---|---|---|
| Degreasing | Alkaline cleaner or solvent | Removes oils, fingerprints |
| Pickling | Nitric-hydrofluoric acid mixture (for scale removal) | Removes heat tint from welding |
| Passivation | 20-25% nitric acid at 50°C for 30 minutes | Restores chromium-rich passive film |
| Rinsing | Deionized water | Removes acid residues |
Common Fabrication Mistakes and Prevention:
| Mistake | Consequence | Prevention |
|---|---|---|
| No back purge on root pass | Sugaring (internal oxidation) | Use argon back purge |
| Excessive heat input (>25 kJ/in) | Grain growth, reduced creep strength | Use stringer beads, not wide weaves |
| Welding without cleaning | Porosity, inclusions | Degrease before welding |
| Grinding with carbon steel wheels | Embedded iron (galvanic corrosion) | Use stainless steel or dedicated wheels |
| Cold working >15% without annealing | Cracking, reduced ductility | Anneal after heavy cold work |
Code Requirements (ASME Section VIII Division 1):
| Parameter | Requirement |
|---|---|
| Allowable stress values | ASME Section II, Part D (Table 1A for N08810) |
| Weld joint efficiency | 1.0 for full RT; 0.85 for spot RT; 0.70 for no RT |
| PWHT exemption | Up to 25 mm thickness, no PWHT required (per ASME) |
Summary: ASTM B409 UNS N08810 plate is readily fabricated and welded using standard techniques. Key requirements include: use ERNiCr-3 filler, back purge for full-penetration welds, control heat input (10-20 kJ/in), and clean/passivate after welding. PWHT is not normally required. Proper fabrication preserves the high-temperature creep strength that distinguishes N08810 from N08800.
