NIMONIC Alloy 901 was developed by the International Nickel Company (INCO) in the UK as a precipitation-strengthened nickel-based superalloy, and it remains a benchmark alloy in the NIMONIC series. Designed specifically for components operating under high stress in the medium-to-high temperature range (≤700 °C) of jet engines, it achieves an optimal balance of strength and corrosion resistance through age-hardening mechanisms. Today, it is extensively utilized in aerospace, energy, and advanced manufacturing industries.

II. Chemical Composition and Microstructure

（1）Chemical Composition (wt%)

Ni:40.0–45.0%，FCC matrix for high-temperature ductility & corrosion resistance

Cr:11.0–14.0%，Oxidation resistance via passivation layer

Fe:12.5–15.0%，Cost reduction and lattice parameter adjustment

Ti:2.4–3.1%，Forms γ′ phase (Ni₃(Al,Ti)) with Al for precipitation strengthening

Al:2.4–2.7%，Works with Ti, enhances oxidation resistance

Mo:2.6–3.1%，Solid solution strengthening, improves creep resistance

Co:0.1–0.6%，Promotes γ′ precipitation and age-hardening response

C:≤0.05%，Controls carbide formation, limits grain boundary embrittlement

S / P:≤0.015%，Impurity elements, strictly controlled to prevent hot cracking

（2）Microstructural Features

Matrix Phase: FCC γ-Ni solid solution provides the ductile foundation.

Strengthening Phase: Uniformly distributed γ′ phase (Ni₃(Al,Ti)), ~15–20% by volume, coherent with matrix and precipitated through aging, ensures high strength.

Secondary Phase: Small amounts of MC-type carbides (e.g., TiC) along grain boundaries prevent grain growth and enhance long-term strength.

III. Mechanical and High-Temperature Properties

（1）Room Temperature Properties

Tensile Strength: ≥1275 MPa

Yield Strength (0.2% offset): ≥1035 MPa

Elongation: ≥20%

Reduction of Area: ≥25%

Hardness (HB): ≥350

（2）High-Temperature Performance

Creep Resistance: At 650 °C and 700 MPa, creep elongation after 1000 hours ≤1%.

Rupture Strength: ≥700 MPa at 650 °C for 1000-hour service.

Oxidation Resistance: ≤0.1 mm/100 h at 800 °C in air (per ASTM G54 standard).

（3）Comparison with Similar Alloys (e.g., Inconel 718)

Superior Mid-Temperature Strength: ~15–20% higher tensile strength at 650 °C.

Machinability: Slightly more challenging due to higher γ′ phase content, though weldability remains comparable.

IV. Processing and Heat Treatment

（1）Hot Working

Forging Temperature: 1050–1150 °C, with >30% deformation to break cast dendrites.

Rolling Temperature: 1000–1100 °C; finish rolling ≥950 °C to avoid work hardening.

（2）Welding Practices

Recommended Methods: TIG and EBW; SMAW is not advised due to porosity risk.

Preparation: Degrease thoroughly; use ERNiCrMo-10 or matching filler metals.

Post-Weld Heat Treatment: 650–700 °C aging for 2–4 hours to relieve residual stress and restore strengthening phase.

（3）Typical Heat Treatment Process

Solution Treatment: 1080 °C for 2 h, air cooling—dissolves γ′ phase and homogenizes matrix.

Aging Treatment: 720 °C for 8 h (air cool) → 620 °C for 8 h (air cool) to promote fine γ′ precipitation and maximize strength.

V. Applications and Representative Components

（1）Aerospace

Engine Components: High-pressure compressor disks, turbine shafts, fasteners (operating at 600–700 °C with cyclic stresses).

Rocket Propulsion: Turbine pump impellers in rocket engines—resistant to fuel corrosion and high-speed load conditions.

（2）Power and Energy

Gas Turbines: Combustor liners and turbine blades in F-class turbines (inlet temp 1200 °C, service temp ≤700 °C).

Nuclear Equipment: Steam generator tubes—resistant to high-temp, high-pressure aqueous corrosion.

（3）Oil & Chemical Industry

Offshore Drilling: BOP valve stems and subsea connectors—resistant to seawater and oil/gas corrosion.

Chemical Reactors: Catalyst support structures under extreme pressure and temperature—resistant to hydrogen and sulfide corrosion.

（4）Advanced Machinery

Turbochargers: Rotor shafts exposed to 900 °C exhaust and 200,000 rpm.

Precision Instruments: Sensor housings for high-temperature environments, ensuring dimensional stability.

VI. Quality Control and Standards

（1）International Standards

ASTM B637 – Specifications for nickel alloy bars and forgings

ISO 9723 – High-temperature tensile testing of superalloys

（2）Specialized Testing

PT (Fluorescent Penetrant Testing): Surface crack inspection

UT (Ultrasonic Testing): Internal defect detection

High-Temperature Creep Testing: per GB/T 2039-2012

VII. Future Development and Alternatives

（1）Optimization Directions

Trace additions of rare earths (Y, Ce) to enhance oxidation resistance

Adjust Ti/Al ratio to improve γ′ phase thermal stability

（2）Replacement Trends

In >750 °C applications, replaced by powder metallurgy alloys (e.g., PM Inconel 718) or single-crystal alloys (e.g., CMSX-4)

However, NIMONIC 901 retains a competitive edge in mid-temperature strength-cost balance

VIII. Conclusion

With its precipitation-strengthened γ′ phase and chromium-enhanced oxidation resistance, NIMONIC Alloy 901 delivers reliable high-temperature performance in the 500–700 °C range. Its widespread adoption in aerospace, energy, and petrochemical applications underscores its enduring value. Despite the rise of newer materials, its mature processing technology and proven reliability ensure NIMONIC 901 remains an irreplaceable choice in medium-temperature, high-stress environments.

IX. About Suzhou Bolaibao Metal

Suzhou Bolaibao Metal is a professional supplier specializing in high-temperature, corrosion-resistant, and special structural alloys. Our product portfolio includes NIMONIC, Inconel, Waspaloy, A286, and more—serving aerospace, nuclear, energy, marine, and chemical sectors. We offer in-stock inventory, precision cutting, heat treatment services, and technical consulting to provide customers with reliable and customized material solutions.
For more information, please visit our website or contact our technical team.

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