CLADDING TECHNOLOGY SHANXI CO., LTDResearch on Arc Cladding Process and Properties of Tungsten Carbide Wear-Resistant Flux-Cored Wire
Literature Overview
This study investigates the arc cladding process and resulting deposit properties when using tungsten carbide (WC)-reinforced flux-cored wire (FCAW) for surface hardening applications. WC-reinforced cladding deposits offer exceptional wear resistance for severe abrasion applications, but the processing challenges are significant: WC is thermodynamically unstable during welding and readily decomposes into tungsten and carbon, leading to reduced hardness and wear performance. The study addresses these challenges through systematic optimization of welding parameters, wire design, and process conditions.
Wire Composition and Microstructure Design
The flux-cored wire was designed with a composite structure consisting of a solid core wire with embedded WC particles and a flux coating. The core wire composition was optimized to promote the formation of hard carbides in the deposit while maintaining adequate weldability.
| Component | Content (wt%) | Role in Deposit |
|---|---|---|
| Fe | Balance | Matrix material |
| Cr | 12-16 | Secondary hardening, oxidation resistance |
| Mo | 4-6 | Thermal stability, carbide formation |
| C | 3.5-5.0 | Primary carbide former |
| V | 2-3 | Fine carbide formation |
| WC (added particles) | 20-30 | Primary hard phase |
| B | 0.3-0.8 | Carbide stability, grain refinement |
The WC particles were added in two size fractions: 10-25 μm (60% of total WC) and 25-50 μm (40% of total WC). The smaller particles provided uniform hardening while the larger particles served as primary wear-resistant sites.
Welding Process Optimization
The FCAW process parameters were systematically varied to determine the optimal window for maintaining WC integrity while achieving good deposit quality:
| Parameter | Low Range | Optimal Range | High Range | Effect |
|---|---|---|---|---|
| Current (A) | 150-180 | 180-220 | 220-260 | Higher current = more WC decomposition |
| Voltage (V) | 24-28 | 28-32 | 32-36 | Higher voltage = wider bead, lower deposition efficiency |
| Travel speed (cm/min) | 4-6 | 6-8 | 8-10 | Faster speed = lower heat input, better WC retention |
| Wire angle (°) | 10-15 | 15-20 | 20-25 | Optimal angle for stable arc and wire feeding |
| Shielding gas flow (L/min) | 10-15 | 15-20 | 20-25 | Adequate protection without turbulence |
The optimal heat input range was determined to be 1.5-2.5 kJ/mm. At heat inputs below 1.5 kJ/mm, incomplete melting of the wire core resulted in poor fusion and porosity. At heat inputs above 2.5 kJ/mm, significant WC decomposition occurred, reducing surface hardness by 20-30%.
Deposit Microstructure and Properties
The microstructure of the optimized cladding deposit consisted of:
- Retained WC particles (5-30 μm, approximately 40-50% of original WC retained)
- M6C (W, Mo, Cr, Fe) carbides (2-8 μm)
- M7C3 (Cr, Fe) carbides (1-5 μm)
- Martensitic matrix with retained austenite (5-15%)
| Property | Value | Comparison to Base Metal |
|---|---|---|
| Surface hardness (HV30) | 850-950 | 4-5x improvement |
| Subsurface hardness (0.5 mm) | 600-700 | 2.5-3x improvement |
| Wear resistance (JCE) | 4.5-5.5x H13 | 2x standard hardfacing |
| Impact toughness (Charpy V) | 20-30 J | Adequate for most applications |
| Crack resistance | No cracking at 180° bend | Good ductility |
| Dilution rate | 15-25% | Acceptable for FCAW |
The hardness gradient from surface to subsurface was gradual, providing a favorable stress distribution during service. The retained austenite in the matrix contributed to both toughness and strain-hardening capacity during wear.
Engineering Application and Performance
The cladding deposits were tested on actual equipment components including:
- Crusher hammers: 18-month service life vs. 6 months for standard H13 cladding
- Conveyor rollers: 24-month service life with periodic regrinding
- Mining bucket teeth: 12-month service life in severe abrasive conditions
The field performance confirmed laboratory results, with wear rates of 0.03-0.08 mm/month compared to 0.2-0.4 mm/month for standard hardfacing electrodes.
Study Insights and Reflections
The most critical finding of this study is that the heat input control is the single most important factor determining the performance of WC-reinforced flux-cored wire cladding. The thermodynamic instability of WC during welding means that every increment of heat input above the optimal range directly translates to reduced hardness and wear resistance. In my engineering experience, this is the most common reason for disappointing field performance: welders tend to use higher currents for productivity, unknowingly degrading the deposit properties. The study provides clear process windows that should be communicated to field welders and enforced through procedural controls. Additionally, the dual-size WC particle distribution (10-25 μm and 25-50 μm) is a sophisticated design feature that provides both uniform hardening and localized wear resistance, a concept that could be extended to other composite cladding applications. This systematic approach to WC cladding wire development and process optimization represents a significant advance in practical surface engineering technology.