Wcco Reinforcement Boosts Gcr15 Steel Wear Resistance Via SLM Method

Imagine a technological breakthrough that could significantly extend the service life of precision bearings while reducing maintenance costs caused by wear. Traditional GCr15 bearing steel often fails under demanding conditions, limiting its applications in high-tech industries. A new study explores the potential of selective laser melting (SLM), an emerging additive manufacturing technique, to produce high-performance WC-Co reinforced GCr15 bearing steel composites that address critical limitations of conventional manufacturing methods.

Selective laser melting (SLM) has gained considerable attention as an advanced additive manufacturing technology. This process utilizes high-energy laser beams to melt metal powder layer by layer, constructing three-dimensional components with complex geometries. SLM's unique characteristics—including micro melt pools (approximately 100 μm), rapid cooling (10 ^6-8 K/s), and cumulative cyclic heat treatment—result in distinctive microstructures and superior mechanical properties.

GCr15 bearing steel is widely used in bearings and molds due to its excellent hardness, strength, wear resistance, and corrosion resistance. However, under harsh conditions, its surface remains susceptible to friction-induced wear. Conventional manufacturing methods often lead to carbide segregation and oversized carbides, further compromising component durability and restricting applications in advanced manufacturing.

Recent research has demonstrated the feasibility of producing particle-reinforced metal matrix composites through SLM. WC-Co, known for its high hardness, low friction coefficient, and high melting point, shows particular promise for enhancing GCr15 bearing steel's wear resistance. This study pioneers the direct incorporation of WC-Co reinforcement into GCr15 bearing steel via SLM technology.

The research employed a mixture of WC-Co particles and GCr15 powder as raw materials. The GCr15 powder had a particle size distribution of 15-53μm, while the WC-Co particles averaged 5μm in diameter. After uniform mixing via ball milling, the powder mixture underwent SLM processing using equipment equipped with a 500W fiber laser.

Key process parameters including laser power, scanning speed, hatch spacing, and layer thickness were optimized to achieve high-density composites with superior mechanical properties.

• SEM and XRD for microstructural and phase composition analysis
• Optical microscopy for microstructure observation
• Vickers hardness testing (200g load, 15s dwell time)
• Ball-on-disc wear testing using Si ₃ N ₄ ceramic balls (5N load, 0.1m/s speed, 1000m sliding distance)
• Wear rate calculation through worn surface cross-sectional area measurement

The SLM-fabricated composites exhibited dense structures with uniform WC-Co particle distribution. The GCr15 matrix displayed fine cellular structures (1-2μm) with nanoscale precipitates at cell boundaries. Excellent interfacial bonding between WC-Co particles and the matrix was observed without significant porosity or cracking.

XRD analysis confirmed the presence of α-Fe, WC, and Co phases without new phase formation, indicating minimal chemical interaction during processing. WC-Co addition refined the matrix grain structure through heterogeneous nucleation.

The composites demonstrated remarkable improvements:

• Significant hardness increase compared to pure GCr15
• Dramatic wear rate reduction
• 10wt.% WC-Co composition achieved 850HV hardness
• Wear rate decreased to 1.2×10 ⁻⁶ mm ³ N ⁻¹ m ⁻¹

The superior hardness stems from WC-Co's intrinsic properties and dislocation motion restriction. During wear, WC-Co particles bear greater loads, reducing matrix wear.

Pure GCr15 showed rough wear surfaces with evident ploughing and debris, characteristic of abrasive wear. WC-Co composites exhibited smoother surfaces with reduced ploughing. Protruding WC-Co particles provided load-bearing capacity and lubrication, effectively suppressing abrasive wear.

• Effective fabrication of well-bonded WC-Co/GCr15 composites via SLM
• Significant grain refinement and mechanical property enhancement
• Effective abrasive wear suppression through WC-Co incorporation

While promising, challenges remain in process optimization, particle distribution control, and cost reduction for industrial adoption. Future research should address these aspects to fully realize SLM's potential in advanced bearing applications.