CLADDING TECHNOLOGY SHANXI CO., LTDTiC-VC Reinforced Wear-Resistant Overlay Welding Microstructure and Performance Analysis
Literature Overview
This study, published in the Journal of Shanghai Jiao Tong University in 2004 by researchers from the Shanghai Jiao Tong University Welding Engineering Institute and Shandong University School of Materials Science and Engineering, investigates the microstructure evolution and tribological performance of overlay weldments reinforced with TiC and VC hard particles. The work addresses a critical engineering challenge in heavy-duty wear applications where conventional alloy overlay weldments suffer from insufficient hardness retention and premature abrasive failure under severe sliding or impact-abrasive conditions. The authors systematically examined the interaction between carbide particles and the weld matrix microstructure, providing valuable insights into the design of particle-reinforced overlay coatings.
Core Technical Content
The fundamental approach involves introducing pre-prepared TiC and VC particles into the weld pool during the overlay welding process to create a composite coating with enhanced wear resistance. The study examined multiple overlay welding techniques including submerged arc welding (SAW) and gas metal arc welding (GMAW) with varying particle sizes, volume fractions, and distribution uniformity. The microstructure analysis revealed that TiC particles exhibit a tendency to dissolve partially during welding, while VC particles maintain better integrity due to their higher melting point (approximately 2830°C for VC versus 3140°C for TiC, though both are thermodynamically stable). The resulting overlay microstructure typically shows a dendritic martensitic or austenitic matrix depending on the base alloy composition, with carbide particles distributed along grain boundaries and within dendrite arms.
Key Microstructural Features
| Feature | TiC-Reinforced Overlay | VC-Reinforced Overlay |
|---|---|---|
| Matrix Structure | Predominantly martensitic (HRC 45-55) | Predominantly austenitic-ferritic (HRC 40-50) |
| Particle Integrity | Partial dissolution observed | Better particle retention |
| Interfacial Bonding | Moderate, with some reaction layer | Strong metallurgical bonding |
| Typical Particle Size | 10-50 μm | 5-30 μm |
| Hardness Contribution | HV 2200-2800 (particle) | HV 2400-2900 (particle) |
| Wear Mechanism | Micro-ploughing and micro-cutting | Micro-cutting with matrix support |
Process Parameters and Their Influence
The welding current, travel speed, and arc voltage directly influence the dilution ratio, particle dissolution rate, and final coating hardness. At higher welding currents (above 400 A for SAW), the increased heat input promotes particle dissolution and coarsening of secondary carbides in the matrix. The optimal process window identified in the study suggests a balance between sufficient wetting and bonding of particles with the matrix while minimizing excessive dissolution. For GMAW processes, current levels of 200-300 A with travel speeds of 150-250 mm/min were found to produce optimal results with particle volume fractions maintained at 15-25%.
Engineering Practice Integration
In practical applications, TiC-VC reinforced overlay weldments have been successfully applied to coal handling equipment, mining machinery, and cement industry components where severe abrasive wear occurs. The key engineering consideration is the substrate preparation—surface roughness of 60-120 μm Ra is recommended to improve mechanical interlocking of particles with the substrate. For multi-pass overlay welding, the first pass should be deposited with a lower particle content (10-15%) to ensure good bonding, while subsequent passes can increase to 20-25% for enhanced surface hardness.
Common Defects and Countermeasures
| Defect Type | Cause | Countermeasure |
|---|---|---|
| Particle agglomeration | Poor pre-mixing of particles with flux/wire | Mechanical mixing with ultrasonic dispersion |
| Cracking at interface | Thermal mismatch and residual stress | Preheating to 150-200°C, post-weld stress relief |
| Excessive dilution | High heat input | Reduce current, increase travel speed |
| Particle floating | Insufficient arc stability | Use of pulsed current modes |
| Poor surface finish | Large particle protrusion | Controlled particle size distribution (max 50 μm) |
Study Insights and Reflections
After reviewing this literature, several important observations emerge. First, the study confirms that a hybrid approach combining both TiC and VC particles in a single overlay can produce synergistic effects, with TiC providing impact resistance and VC contributing to fine abrasive wear resistance. Second, the microstructural analysis reveals that the bond strength between particles and matrix is more critical for long-term wear performance than the particle hardness alone—a point that is often overlooked in industrial practice. Third, the work highlights the importance of post-weld heat treatment: a tempering cycle at 550-600°C for 2 hours can relieve residual stresses while maintaining overall coating hardness above HRC 55.
The practical implication for engineers is that particle-reinforced overlay welding represents a cost-effective alternative to hardfacing with expensive cobalt-chromium alloys, particularly in applications where the wear mechanism is predominantly sliding abrasion rather than erosion-corrosion. However, the process requires careful control of particle size distribution, volume fraction, and welding parameters to achieve reliable, repeatable results. Future work should focus on optimizing particle shape (spherical versus irregular) and exploring nano-sized carbide reinforcements for even finer microstructural control.