Haynes188 Alloy

Haynes188 (designated as UNS R30188) is a premium cobalt-chromium-nickel-tungsten (Co-Cr-Ni-W) based solid solution strengthened wrought superalloy, engineered for ultra-high-temperature service scenarios demanding exceptional thermal stability, oxidation resistance, and thermal corrosion resistance. Distinguished from Haynes25 (Co-Cr-Ni-W, optimized for 650-1095℃) and Haynes75 (Ni-Cr, for ≤650℃), Haynes188 achieves superior ultra-high-temperature performance through the synergistic solid solution effect of chromium (Cr), tungsten (W), and molybdenum (Mo) — with no reliance on precipitation strengthening. Taking cobalt as the matrix, it maintains excellent ductility and thermal fatigue resistance even at 1200℃, making it a core material for components exposed to extreme heat, cyclic thermal stress, and harsh corrosive media (e.g., sulfur-containing flue gas, molten salt).

Notably, Haynes188 forms a dense, self-healing Cr₂O₃-Al₂O₃-WO₃ composite oxide film at ultra-high temperatures, providing long-term protection against oxidation and thermal corrosion. Its outstanding hot workability and weldability enable the fabrication of thin-walled, complex-shaped components (e.g., combustion chamber liners, heat shields), and it is widely used in aerospace propulsion, energy, and metallurgy industries where performance at 1000-1200℃ is critical. The following is a comprehensive breakdown of its chemical composition, physical properties, mechanical properties, and application products.

1. Chemical Composition (Mass Fraction, %)

2. Physical Properties

2.1 Basic Physical Parameters

• Density: Approximately 9.15g/cm³ at room temperature (25℃), slightly higher than Haynes25 (9.13g/cm³) due to optimized W content, but its ultra-high-temperature performance outweighs weight concerns for critical components (e.g., rocket engine nozzles).
• Melting Temperature Range: 1370-1430℃ (liquidus: ~1430℃; solidus: ~1370℃). The narrow, stable melting range ensures uniform solidification during casting and consistent deformation during hot working, reducing internal defects (e.g., segregation, shrinkage porosity) for high-stress ultra-high-temperature parts.
• Thermal Expansion Coefficient (CTE):

◦ 20-100℃: ~12.8×10⁻⁶/℃

◦ 20-600℃: ~14.5×10⁻⁶/℃

◦ 20-1000℃: ~16.2×10⁻⁶/℃

◦ 20-1200℃: ~17.0×10⁻⁶/℃

The gradual CTE increase minimizes thermal stress during rapid temperature cycling (e.g., hypersonic aircraft ascent/descent, industrial furnace start-stop), reducing thermal fatigue cracking risk by 50-60% compared to Haynes25 and 310S stainless steel.

• Thermal Conductivity (λ):

◦ 100℃: ~14.0W/(m·K)

◦ 500℃: ~17.5W/(m·K)

◦ 1000℃: ~21.0W/(m·K)

◦ 1200℃: ~23.5W/(m·K)

Temperature-dependent conductivity improvement promotes efficient heat dissipation, avoiding localized overheating (a major cause of creep acceleration) and extending service life by 35-40% compared to Haynes25.

• Electrical Resistivity (ρ):

◦ Room temperature (25℃): 140-150×10⁻⁸Ω·m

◦ 1000℃: 190-200×10⁻⁸Ω·m

High resistivity reduces eddy current losses in high-frequency heating components (e.g., induction furnace parts), making it suitable for electromagnetic heating applications.

2.2 Magnetic Properties

• Magnetic Permeability (μ): ~1.010-1.018μ₀ (at H=800A/m, room temperature) — weakly magnetic at ambient temperature;
• Temperature-dependent Magnetism: Magnetic permeability decreases with increasing temperature, becoming nearly non-magnetic (μ≈1.002-1.003μ₀) in the service range (1000-1200℃);
• Coercivity (Hc): ~160-240A/m (room temperature) — significantly higher than soft magnetic alloys, ensuring no interference with magnetic sensors in aerospace/industrial equipment.

3. Mechanical Properties (After Standard Heat Treatment: 1150-1200℃ solid solution for 1h, air cooling)

Key Notes:

• Exceptional Ultra-high-temperature Ductility: At 1200℃, elongation (≥10%) and reduction of area (≥15%) prevent brittle fracture during emergency shutdowns — a critical advantage over brittle high-temperature ceramics;
• Superior Creep Resistance: At 1000℃, 1000h creep rupture strength (≥180MPa) is 12.5% higher than Haynes25, ensuring long-term structural stability for components under continuous ultra-high-temperature load (e.g., furnace liners);
• Balanced Room-temperature Performance: Tensile strength (≥850MPa) and elongation (≥20%) enable easy forming of complex shapes (e.g., curved heat shields) via stamping, rolling, or welding.

4. Ultra-high-temperature Oxidation & Corrosion Resistance (Core Performance)

Key Notes:

• Self-healing Oxide Film: The Cr₂O₃-Al₂O₃-WO₃ composite film repairs micro-cracks during thermal cycling, maintaining long-term protection — superior to single-layer Cr₂O₃ films in Haynes25;
• Excellent Thermal Corrosion Resistance: In sulfur-containing environments, it outperforms nickel-based alloys (e.g., Inconel 600) by 40-50% in corrosion resistance, making it ideal for coal-fired power plant components.

5. Application Products & Industry Scenarios

5.1 Aerospace & Defense Field

As a benchmark for ultra-high-temperature aerospace components, Haynes188 is used for:

• Hypersonic Aircraft Propulsion: Combustion chamber liners and nozzle throats in scramjet engines (Mach 5-8), withstanding 1100-1200℃ aerodynamic heating and high-temperature gas erosion; the alloy’s thermal fatigue resistance reduces deformation by 50% compared to Haynes25;
• Rocket Engine Components: Thrust chamber liners and exhaust nozzles in liquid rocket engines (propellants: liquid oxygen/kerosene), resisting 1200-1300℃ combustion gas and thermal shock; service life extended to 50+ launches;
• Aerospace Thermal Protection: Honeycomb heat shields for reentry vehicles (e.g., space capsules), resisting 1000-1150℃ reentry heating; thin-walled (0.3-0.5mm) structures reduce weight by 15-20% vs. Haynes25 shields.

5.2 Energy & Power Generation Field

In ultra-high-temperature energy systems, Haynes188 is applied to:

• Coal-fired Power Plant Components: Superheater tubes and boiler headers in ultra-supercritical (USC) power plants (steam temperature: 700℃), resisting sulfur-containing flue gas corrosion; service life extended by 2-3 times vs. 310S stainless steel;
• Molten Salt Energy Storage: Heat exchanger tubes in molten salt energy storage systems (heat transfer fluid: nitrate, 565-600℃), withstanding molten salt corrosion and thermal cycling; heat exchange efficiency improved by 15-20%;
• Nuclear Energy (Advanced Reactors): Core auxiliary components (fuel handling tools) in molten salt reactors (MSRs), resisting molten fluoride salt corrosion (800-850℃) and weak neutron radiation.

5.3 Industrial Heating & Metallurgy Field

In ultra-high-temperature industrial furnaces and metallurgical processes, Haynes188 is used for:

• Ultra-high-temperature Furnace Liners: Inner liners of vacuum sintering furnaces (1100-1200℃) for superalloy heat treatment, ensuring uniform temperature distribution (±5℃) and resisting oxidation; service life extended by 80-90% vs. Haynes25;
• Heating Element Assemblies: Support brackets and protective sleeves for silicon carbide (SiC) heating elements (1100-1200℃), withstanding radiant heat and mechanical vibration;
• Metallurgical Conveyors: Mesh belts for continuous annealing lines (stainless steel, 1000-1050℃), resisting high-temperature wear and thermal fatigue; replacement cycle extended from 6 months to 2 years.

5.4 Automotive & High-performance Machinery Field

In specialized high-temperature automotive and machinery applications, Haynes188 is used for:

• Racing Car Exhaust Systems: Exhaust headers and turbocharger casings for Formula 1 and endurance racing cars, resisting 900-1000℃ exhaust gas corrosion and thermal cycling; weight reduced by 25% vs. cast iron;
• High-temperature Pumps & Valves: Valve stems and impellers in high-temperature molten metal pumps (e.g., aluminum alloy casting), withstanding 800-900℃ molten metal erosion and ensuring leak-free operation.
• Hot Working: Forging temperature range: 1180-1250℃; initial forging temp ≤1250℃ (avoid grain coarsening), final forging temp ≥1050℃ (prevent work hardening); hot rolling for sheets (thickness 0.3-50mm) with 30-40% reduction per pass;
• Cold Working: Cold rolling, stamping, or bending at room temperature, with total deformation up to 50-60% for sheets; intermediate annealing (1100-1150℃, 1h, air cooling) after 20-25% deformation to restore ductility;
• Welding: Highly weldable via TIG, MIG, electron beam, and laser welding. Recommended filler metal: Co-Cr-Ni-W-Mo alloy (matching Haynes188 composition); preheating (200-300℃ for thick plates ≥10mm); post-weld heat treatment (1150-1200℃ solid solution for 1h, air cooling) to eliminate stress and restore corrosion resistance;
• Machining: Best performed in solution-treated (soft) state (HRC 30-35) using carbide or ceramic tools; cutting fluids recommended to reduce tool wear; finish machining (grinding) achievable to tolerance ±0.01mm for precision components (e.g., turbine parts).

6. Processing & Welding Recommendations

This comprehensive performance and application profile establishes Haynes188 as the top-tier ultra-high-temperature alloy in the Haynes series. Its unique combination of ultra-high-temperature stability, oxidation/corrosion resistance, and processability makes it irreplaceable for the most demanding components in aerospace, energy, and metallurgy — where performance at 1000-1200℃ directly determines system reliability and efficiency.