1. Chemical Composition and Alloy Design

The chemical composition of GW18Cr5V is optimized with tungsten (W), chromium (Cr), and vanadium (V) as the main alloying elements to ensure high hardness and stability at elevated temperatures.

(1) Standard Composition (GB/T 3086-2020)

Carbon (C)：0.90–1.05；Forms carbides, improves hardness and wear resistance

Tungsten (W)：17.0–19.0；Enhances red hardness, forms stable carbides (W₂C, WC)

Chromium (Cr)：4.5–5.5；Improves hardenability, oxidation, and corrosion resistance

Vanadium (V)：0.7–1.2；Refines grains, enhances wear resistance and toughness

Manganese (Mn)：≤0.40；Deoxidation, improves hot workability

Silicon (Si)：≤0.40；Deoxidation, improves temper stability

Phosphorus (P)：≤0.030；Reduces cold brittleness

Sulfur (S)：≤0.030；Reduces hot brittleness

(2) Alloying Element Mechanisms

Tungsten (W):
Forms W₂C and WC carbides at high temperatures, significantly boosting red hardness (maintains HRC≥58 at 600°C). It also inhibits austenite grain growth, improving high-temperature strength.

Chromium (Cr):
Increases hardenability for uniform hardening in large bearings; forms Cr₂₃C₆ carbides enhancing wear resistance; develops a Cr₂O₃ oxide film on the surface to improve oxidation resistance.

Vanadium (V):
Forms VC carbides, refines grain size, and improves impact toughness; prevents carbide aggregation, enhancing high-temperature stability.

2. Microstructure and Mechanical Properties

(1) Typical Microstructure

Annealed state: spheroidized pearlite + uniformly distributed alloy carbides (WC, VC, Cr₂₃C₆).

Quenched state: high-alloy martensite + retained austenite (<5%) + undissolved carbides.

Tempered state: tempered martensite + finely dispersed secondary hardening carbides (W₂C, VC).

(2) Mechanical Properties (after heat treatment)

Room Temperature Hardness：HRC 60–64

Test Condition：After quenching & tempering

High-Temperature Hardness (600°C)：≥HRC 58

Test Condition：High-temp hardness tester

Bending Strength (σbb)：≥3500 MPa

Test Condition：Three-point bending test

Impact Toughness (AKU)：≥15 J

Test Condition：Charpy impact test

Elastic Modulus (E)：210–220 GPa

Test Condition：Dynamic modulus test

(3) High-Temperature Performance Advantages

Red hardness: Maintains HRC≥58 at 600°C, superior to ordinary bearing steels like GCr15 which soften above 300°C.

Creep resistance: High tungsten content suppresses high-temperature deformation, suitable for long-term high-temperature operation.

Oxidation resistance: The Cr₂O₃ film protects against oxidation and corrosion below 800°C.

3. Heat Treatment Process

The heat treatment process critically influences GW18Cr5V’s final properties, including spheroidizing annealing, quenching, and tempering.

(1) Spheroidizing Annealing (Softening Treatment)

Purpose: Reduce hardness (≤255 HB) for improved machinability.

Process: Heat to 780–820°C, hold for 2–4 hours; slow cool to 500°C, then air cool.

Microstructure: Spheroidized carbides + ferrite matrix.

(2) Quenching (Austenitizing + Rapid Cooling)

Temperature: 1220–1250°C (high temperature required to dissolve carbides in high tungsten steel).

Cooling method: Oil quenching or staged quenching (salt bath) to minimize deformation.

Microstructure: High-alloy martensite + 5–10% retained austenite + undissolved carbides.

(3) Tempering (Secondary Hardening)

Conditions: 540–560°C × 2–3 cycles, 2 hours each.

Mechanism: Martensite decomposition precipitates nano-carbides (W₂C, VC) for secondary hardening; retained austenite transforms to martensite (cryogenic treatment may further reduce residual austenite).

Final hardness: HRC 62–64.

4. Typical Applications

GW18Cr5V is mainly used in extreme high-temperature, high-speed, and heavy-load bearing applications such as:

（1）Aerospace:
Main shaft bearings of aircraft engines (turbine and compressor bearings), rocket engine high-speed bearings requiring heat and impact resistance.

（2）Energy & Power Machinery:

Gas turbine bearings operating in hot gas environments at 600°C for extended periods; nuclear power cooling pump bearings needing radiation and heat resistance.

（3）Industrial Heavy Equipment:
Metallurgical rolling mill bearings under heavy load and hot rolling conditions; high-temperature pump and valve bearings in chemical and petroleum industries.

5.Comparison with Other High-Temperature Bearing Steels

（1）GW18Cr5V

Main Composition：W18Cr5V

Max Service Temperature：600°C

Advantages：Best red hardness, wear resistance

Disadvantages：High cost, difficult machining

（2）M50 (4Cr4Mo2V)

Main Composition：Mo-based

Max Service Temperature：430°C

Advantages：Good overall performance

Disadvantages：Insufficient high-temp properties

（3）CSS-42L

Main Composition：Co-Ni-Cr

Max Service Temperature：800°C

Advantages：Ultra-high corrosion resistance

Disadvantages：Expensive

（4）G13Cr4Mo4Ni4V

Main Composition：Ni-Mo-based

Max Service Temperature：500°C

Advantages：Good toughness

Disadvantages：Moderate red hardness

6. Research Advances and Trends

Nano-carbide strengthening: Optimizing carbide distribution via controlled rolling/cooling and cryogenic treatment to improve toughness.

Surface modification: Applying PVD/CVD coatings (e.g., TiAlN) to enhance wear resistance further.

3D printing applications: Exploring powder metallurgy combined with laser additive manufacturing to reduce material waste.

7. Conclusion

Thanks to its tungsten, chromium, and vanadium alloy design, GW18Cr5V is a top-tier high-temperature bearing steel suitable for aerospace, energy, and heavy machinery in extreme environments. Its performance hinges on precise heat treatment processes, with future directions including nano-strengthening, surface modification, and additive manufacturing technologies.

8. About Suzhou Bolaibao Metal

Suzhou Bolaibao Metal specializes in the development and supply of high-performance special steels, high-temperature alloys, and titanium alloys. We are committed to providing premium solutions to advanced manufacturing industries such as aerospace, energy equipment, precision machinery, and petrochemicals. Through rigorous quality control and professional technical support, we help our clients enhance product competitiveness and foster innovation across industries.

Feel free to contact us for technical support, product information, or tailored solutions.

Website: www.blbszmetal.com
Email: sale@bolaibao1.com

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