GH90 Alloy

GH90 is a high-performance nickel-copper (Ni-Cu) based precipitation-hardening wrought superalloy, specifically designed for medium-to-high temperature service scenarios requiring excellent corrosion resistance, balanced mechanical properties, and good processability. It achieves strengthening primarily through the coherent precipitation of γ’ phase (Ni₃Al, Ti) — the core strengthening phase — and is supplemented by solid solution strengthening from copper (Cu) and chromium (Cr). Unlike high-temperature nickel-based alloys such as GH4738 (focused on ultra-high-temperature creep resistance), GH90 is optimized for medium-temperature environments, enabling reliable long-term operation in harsh conditions ranging from 600℃ to 850℃.

Notably, GH90 exhibits superior resistance to corrosion by seawater, salt spray, and weak acidic/alkaline media (thanks to its Ni-Cu matrix), while forming a dense Cr₂O₃-Al₂O₃ oxide film at high temperatures to resist oxidation. It retains excellent hot workability and weldability, making it suitable for manufacturing large-scale complex components (e.g., marine engine parts, chemical reactor internals). It is widely used in marine engineering, petrochemical, and medium-temperature energy equipment, where material corrosion resistance and medium-temperature strength are critical. The following is a comprehensive breakdown of its chemical composition, physical properties, and application products.

1. Chemical Composition (Mass Fraction, %)

2. Physical Properties

2.1 Basic Physical Parameters

• Density: Approximately 8.25g/cm³ at room temperature (25℃), slightly lower than Ni-Cr-based GH4738 (8.45g/cm³) due to Cu addition, and 5-7% lower than high-W nickel-based alloys such as GH3128 (8.70g/cm³). This low-density advantage is critical for weight-sensitive medium-temperature components (e.g., marine engine exhaust manifolds), reducing equipment overall weight by 3-8% compared to corrosion-resistant alloys like Monel 400.
• Magnetic Properties: Weakly magnetic at room temperature (magnetic permeability μᵣ ≈ 1.003-1.008); magnetic property gradually fades as temperature rises, becoming nearly non-magnetic (μᵣ ≈ 1.001-1.002) in the service temperature range (600-850℃). This makes it suitable for applications near general electromagnetic equipment, though caution is needed for high-precision magnetic sensors (e.g., marine navigation systems).
• Melting Temperature Range: 1320-1380℃ (liquidus: ~1380℃; solidus: ~1320℃). The narrow and stable melting range ensures uniform solidification during casting and consistent deformation during forging, reducing internal defects (e.g., shrinkage porosity, segregation) and improving structural integrity—critical for large-scale welded components such as marine pipeline systems.
• Thermal Expansion Coefficient (CTE):

2.2 Thermal Properties

◦ 20-100℃: ~12.8×10⁻⁶/℃

◦ 20-600℃: ~14.3×10⁻⁶/℃

◦ 20-800℃: ~15.6×10⁻⁶/℃

◦ 20-850℃: ~15.9×10⁻⁶/℃

The gradual CTE increase minimizes thermal stress during frequent temperature cycling (e.g., marine engine start-stop, chemical reactor load adjustment), reducing thermal fatigue cracking risk by 40-50% compared to Ni-Cu alloys like Monel K-500.

• Thermal Conductivity (λ):

◦ 100℃: ~16.2W/(m·K)

◦ 500℃: ~19.5W/(m·K)

◦ 800℃: ~22.8W/(m·K)

◦ 850℃: ~23.5W/(m·K)

The temperature-dependent conductivity improvement promotes efficient heat transfer in medium-temperature components, avoiding localized overheating (a major cause of material softening) and extending part service life by 25-30% compared to conventional Ni-Cu alloys.

2.3 Mechanical Properties (After Standard Heat Treatment: 1050-1080℃ solid solution for 1h, water cooling + 700-730℃ aging for 16h, air cooling)

Key Notes:

• The high room-temperature strength (σᵦ ≥900MPa) meets the load-bearing requirements of marine engine components and high-pressure chemical valves, with strength 30-35% higher than Monel 400;
• At 700℃ (a typical service temperature for petrochemical reactor internals), the creep rupture strength (≥380MPa) is 25-30% higher than that of Monel K-500, ensuring long-term structural stability under medium-temperature load;
• Even at 850℃ (near its upper service limit), the retained elongation (≥10%) prevents brittle fracture during emergency shutdowns, making it suitable for components with frequent thermal cycling (e.g., marine exhaust systems).

3. Application Products & Industry Scenarios

3.1 Marine Engineering Field

As a core corrosion-resistant material for marine high-temperature components, GH90 is used for:

• Marine Engine Parts: Exhaust manifolds and turbocharger casings in large marine diesel engines (operating temperature: 600-750℃), resisting corrosion by seawater salt spray and high-temperature exhaust gas; the alloy’s corrosion resistance extends maintenance intervals by 24-30 months;
• Marine Pipeline Systems: High-temperature oil pipelines and cooling water pipes in offshore oil platforms, withstanding 650-700℃ medium and seawater erosion; its good weldability simplifies pipeline assembly and reduces leakage risks;
• Underwater Structural Parts: Submarine propulsion system components (e.g., propeller shafts, pump casings), resisting deep-sea corrosion and ensuring structural integrity for over 10 years of service.

3.2 Petrochemical Field

In medium-scale petrochemical and chemical processing units (operating temperature: 600-800℃), GH90 is applied to:

• Chemical Reactor Internals: Catalyst support grids and reactor liners in ethylene production units, resisting corrosion by hydrocarbon media and high-temperature steam; compared to Monel K-500, it extends service life by 40-50% and reduces maintenance costs by 35-40%;
• High-temperature Valves: Gate valves and control valves in high-temperature oil pipelines (pressure: 15-20MPa), withstanding medium corrosion and cyclic thermal stress; its creep resistance ensures seal integrity for over 80,000 hours;
• Heat Exchanger Tubes: Tubes in shell-and-tube heat exchangers for crude oil refining, resisting 650-750℃ oil and water corrosion; the alloy’s thermal conductivity improves heat exchange efficiency by 15-20%.

3.3 Energy Field

3.3.1 Medium-temperature Thermal Power Generation

In subcritical thermal power plants (steam parameters: 500-550℃, 16-18MPa), GH90 is used for:

• Medium-temperature Steam Headers: Headers connecting superheaters and reheaters, withstanding high-temperature steam erosion and thermal fatigue; its corrosion resistance reduces scaling and improves heat transfer efficiency;
• Feedwater Pump Components: Impellers and shafts in high-temperature feedwater pumps, resisting 500-550℃ water corrosion and ensuring pump operation reliability.

3.3.2 Solar Thermal Power Generation

For parabolic trough solar thermal power plants (heat transfer fluid temperature: 390-420℃), the alloy is used for:

• Heat Absorber Tube Supports: Support structures for heat absorber tubes, resisting outdoor UV radiation and high-temperature heat transfer fluid erosion;
• Heat Exchanger Plates: Plates in steam generators, where its good thermal conductivity ensures efficient heat transfer from heat transfer fluid to water.
• Metallurgical Industry: High-temperature furnace belts (working temperature: 650-750℃) for stainless steel annealing, withstanding air oxidation and mechanical wear; its corrosion resistance extends belt service life by 60-70% compared to 309S stainless steel;
• Automotive Industry: Exhaust manifolds for high-performance racing cars and heavy-duty trucks, resisting 600-700℃ exhaust gas corrosion and reducing manifold weight by 18-25% compared to cast iron;
• High-temperature Test Equipment: Sample holders for medium-temperature corrosion testing (600-850℃) and low-load fixture components, providing stable support for long-term tests (up to 6,000 hours) and ensuring accurate test data.
• Hot Working: Forging temperature range: 1100-1160℃; initial forging temperature should not exceed 1160℃ to avoid grain coarsening, and final forging temperature should not be lower than 950℃ to prevent work hardening and cracking;
• Cold Working: Cold rolling, stamping, or bending can be performed at room temperature, with intermediate annealing (980-1020℃, 1h) recommended after 25-35% deformation to restore ductility—cold workability is significantly better than high-temperature nickel-based alloys like GH4738;
• Heat Treatment: The two-step process (solid solution + aging) must be strictly controlled—over-aging (above 760℃) will cause γ’ phase coarsening (particle size >0.4μm) and significant strength degradation, while under-aging (below 680℃) will result in insufficient precipitation strengthening and reduced medium-temperature performance.

3.4 Metallurgical & Other Industrial Fields

4. Processing & Heat Treatment Recommendations

This comprehensive performance and application profile makes GH90 a cost-effective, corrosion-resistant superalloy for medium-temperature industrial manufacturing, perfectly balancing medium-temperature strength, corrosion resistance, and processability for large-scale, complex-shaped components in marine, petrochemical, and energy industries.