Material selection is critical for high-temperature pumps operating in power generation, oil refining, chemical processing, and industrial heating. Proper material selection ensures mechanical integrity, corrosion resistance, and long service life at elevated temperatures. This guide covers alloy and refractory material selection for high-temperature pumps.
Temperature Ranges and Material Classes
| Temp Range | Material Class | Typical Materials | Applications |
|---|---|---|---|
| <150°C | Standard stainless | 316L, CF8M | General chemical, water |
| 150-300°C | High-temp stainless | 316, 310, CF8M | Hot water, thermal oil, mild chemical |
| 300-450°C | Alloy steel | 1.25Cr-0.5Mo, 2.25Cr-1Mo, F11, F22 | Thermal oil, boiler feed, refinery |
| 450-600°C | High-alloy / duplex | 310S, 321, 347, HK40, HP | Hot oil, molten salt, refinery |
| 600-800°C | Heat-resistant alloy | HK40, HP, Incoloy 800, Hastelloy X | Molten salt, high-temp process |
| >800°C | Superalloy / refractory | Inconel 600/625, Haynes 230, ceramic | Extreme high temp, specialty |
Cast and Wrought Alloys
Carbon and Low-Alloy Steels
- WCB (cast carbon steel): Up to 425°C, general service, low cost. Not for corrosive service.
- WCC (cast carbon steel): Similar to WCB, higher strength.
- 1.25Cr-0.5Mo (F11/F12): Up to 500°C, good high-temp strength, refinery/thermal oil.
- 2.25Cr-1Mo (F22): Up to 550°C, excellent high-temp strength, hydrogen resistance, refinery hydroprocessing.
- 5Cr-0.5Mo (F5): Up to 600°C, corrosion resistance, sulfidation resistance.
- 9Cr-1Mo (F9): Up to 650°C, excellent high-temp strength, steam service.
Stainless Steels
- 304/CF8: Up to 400°C, general corrosion, not for high chloride.
- 316/CF8M: Up to 450°C, molybdenum for pitting resistance, general chemical.
- 310S/CK20: Up to 1000°C (oxidation), excellent high-temp oxidation resistance, thermal cycling.
- 321/CF8C: Up to 800°C, titanium-stabilized, resists intergranular corrosion, thermal cycling.
- 347: Up to 800°C, niobium-stabilized, similar to 321, better weldability.
- Duplex (2205/CD4MCu): Up to 250°C, high strength, chloride resistance, not for high temp (475°C embrittlement).
Heat-Resistant Cast Alloys
- HK40 (25Cr-20Ni): Up to 1050°C, excellent oxidation resistance, furnace rolls, radiant tubes.
- HP (25Cr-35Ni): Up to 1100°C, better than HK40, higher creep strength, ethylene cracking tubes.
- HU (19Cr-39Ni): Up to 1150°C, maximum heat resistance, specialty.
- HW (16Cr-36Ni): Up to 1100°C, thermal fatigue resistance.
- These alloys are used for pump components in extreme high-temp service
Nickel-Based Superalloys
- Inconel 600: Up to 1100°C, excellent oxidation, chloride stress corrosion resistance.
- Inconel 625: Up to 980°C, excellent strength and corrosion, seawater, acid.
- Incoloy 800/800H: Up to 1100°C, good high-temp strength, cost-effective.
- Hastelloy C-276: Up to 700°C, excellent corrosion (acid, chloride), high cost.
- Hastelloy X: Up to 1200°C, excellent oxidation, gas turbine components.
- Haynes 230: Up to 1150°C, excellent thermal stability, nitriding resistance.
Component-Specific Material Selection
Casing / Volute
- Most critical pressure-containing component
- <150°C: 316L/CF8M
- 150-400°C: 316/CF8M or WCB (non-corrosive)
- 400-550°C: 2.25Cr-1Mo (F22) or 310S
- 550-800°C: HK40, HP, Incoloy 800
- >800°C: Inconel 600/625, Hastelloy X
- Consider: cast vs wrought, weldability, inspection requirements
Impeller
- Subject to high stress and corrosion
- Must match casing material (galvanic compatibility)
- High temp: use higher strength material than casing
- Typical: 316, 310S, Inconel 625, Hastelloy C
- Consider: casting quality, NDT requirements, dynamic balancing
Shaft
- High torsional and bending stress at high temp
- Must resist creep and fatigue
- <400°C: 316, 17-4PH
- 400-600°C: 2.25Cr-1Mo, F22, 310S
- >600°C: Inconel 718, Waspaloy, A286
- Consider: surface treatment (nitriding, Stellite coating) for wear resistance
Shaft Sleeve / Wear Rings
- Subject to wear and corrosion
- Materials: 316, 310S, Stellite 6/12, tungsten carbide, ceramic (Al₂O₃, SiC)
- High temp: Stellite or tungsten carbide
- Consider: hardness, corrosion resistance, galling resistance
Mechanical Seal Components
- Seal faces: SiC vs SiC (high temp), SiC vs carbon (general), tungsten carbide
- Springs: Inconel 718, Hastelloy C (high temp/corrosion)
- Elastomers: limited to <200°C; above use metal bellows or PTFE wedge
- Metal bellows: Inconel 718, Hastelloy C (for >200°C)
- Gaskets: spiral wound (316/PTFE or 316/graphite), camprofile, RTJ (high pressure)
Bearings
- Standard bearings: up to 120°C (grease), 150°C (oil)
- High temp: use oil circulation with cooler, or magnetic coupling
- Bearing material: 52100 steel (standard), M50 tool steel (high temp), ceramic (hybrid)
- Consider: bearing housing cooling fins, water cooling, oil mist
Corrosion Considerations
High-Temperature Oxidation
- Forms protective oxide layer (Cr₂O₃ for stainless, Al₂O₃ for aluminized)
- Chrome content >12% for oxidation resistance
- 310S (25Cr-20Ni): excellent up to 1000°C
- Inconel 600: excellent up to 1100°C
- Thermal cycling can spall oxide layer — use stabilized grades (321, 347)
Sulfidation
- Occurs in high-sulfur environments (refinery, sour gas)
- Chrome content improves sulfidation resistance
- 5Cr-0.5Mo (F5): good sulfidation resistance
- 9Cr-1Mo (F9): excellent sulfidation resistance
- Aluminum diffusion coating: excellent sulfidation resistance
Carburization
- Occurs in high-carbon environments (ethylene cracking, heat treating)
- High nickel alloys resist carburization
- HK40, HP: standard for carburizing environments
- Aluminum-containing alloys: excellent carburization resistance
Hydrogen Attack
- Occurs in high-pressure hydrogen (refinery hydroprocessing)
- Use Cr-Mo steels (2.25Cr-1Mo) per API 941 (Nelson curves)
- Stabilized stainless (321, 347) for higher temp
- Post-weld heat treatment required for Cr-Mo steels
Molten Salt Corrosion
- Molten nitrate salts (solar thermal): 300-600°C, use 316/304
- Molten chloride salts (next-gen): 500-800°C, use Inconel 625, Hastelloy C
- Molten fluoride salts (nuclear): 500-700°C, use Hastelloy N, Inconel
- Consider: impurity effects, flow velocity, temperature gradients
Mechanical Properties at High Temperature
Creep Resistance
- Creep: time-dependent deformation under constant load at high temp
- Critical for pressure-containing components (casing, shaft)
- Use creep-resistant alloys: 2.25Cr-1Mo, 9Cr-1Mo, 310S, Inconel
- Design per API 610 / ASME Section VIII (stress rupture data)
- 100,000-hour creep rupture strength is key design parameter
Thermal Fatigue
- Caused by thermal cycling (startup/shutdown, load changes)
- Use materials with good thermal fatigue resistance: 321, 347, Incoloy 800
- Design: minimize thermal gradients, use centerline support, avoid stress concentrations
- Consider: preheat/postheat for welding, controlled heating/cooling rates
Thermal Expansion
- Different materials have different coefficients of thermal expansion (CTE)
- Mismatch causes thermal stress at joints and fits
- Use compatible materials (similar CTE) for mating parts
- Design: allow for thermal growth (centerline support, flexible coupling)
- Typical CTE: carbon steel 12e-6/°C, 316 16e-6/°C, Inconel 13e-6/°C
Refractory and Ceramic Materials
Refractory Linings
- Used for extreme temp (>800°C) or abrasive high-temp service
- Materials: alumina (Al₂O₃), silica (SiO₂), magnesia (MgO), chrome-magnesite
- Application: castable, brick, plastic, gunning
- Consider: thermal conductivity, abrasion resistance, chemical compatibility
- Used in: molten metal pumps, furnace circulation pumps, slag pumps
Ceramic Components
- Silicon carbide (SiC): Seal faces, wear rings, bearings — excellent hardness and corrosion
- Alumina (Al₂O₃): Shaft sleeves, wear parts — cost-effective, good wear
- Zirconia (ZrO₂): High toughness, thermal shock resistance
- Silicon nitride (Si₃N₄): High strength, thermal shock, bearing balls
- Consider: brittleness, thermal shock, machining difficulty, cost
Coatings and Cladding
- Stellite: Cobalt-based, wear/corrosion resistant, applied by weld overlay
- HVOF (WC-Co, Cr₃C₂-NiCr): High hardness, wear resistance, shaft sleeves
- Aluminum diffusion: Sulfidation/carburization resistance
- Chromium carbide: Wear resistance at high temp
- PTFE/PFA lining: Corrosion resistance (limited to <200°C)
- Consider: coating adhesion, thermal expansion match, repairability
Procurement Recommendations
- Provide: fluid composition, temperature range, pressure, corrosion characteristics, startup/shutdown cycles
- Specify materials per API 610 / ASME standards for high-temp service
- For 300-550°C: specify 2.25Cr-1Mo (F22) casing, 310S or Inconel shaft
- For 550-800°C: specify HK40/HP casing, Inconel 625 shaft and impeller
- For >800°C: specify Inconel/Hastelloy, consider refractory lining
- For corrosive service: specify Hastelloy C-276 or Inconel 625 wetted parts
- For high-temp seals: specify metal bellows seal (Inconel 718), SiC faces
- Require material test reports (MTR) per EN 10204 3.1/3.2
- Require NDT: radiography, ultrasonic, dye penetrant per API 610
- Require post-weld heat treatment for Cr-Mo steels
- Include spare parts: wear rings, shaft sleeves, seals, impeller
- Require factory performance test at operating temp (if possible)
Related Industries
High-temperature material selection principles apply to oil and gas (refinery, upstream), power generation (fossil, nuclear, solar), chemical processing, metals processing, and aerospace. The core principle — select materials based on temperature, corrosion, creep, and thermal fatigue requirements — is consistent across high-temperature industries.