Dual-Wire Flux-Cored Wire High-Efficiency Hardfacing Technology

Literature Overview

This research, published in Journal of Qingdao University of Science and Technology (Natural Science Edition, 2012, Vol. 33, No. 4, pp. 409–412) by Zhao Cheng and Zhao Liting from the College of Mechanical and Electrical Engineering and the Surface Technology Research Institute, investigates a novel dual-wire hardfacing technique using YJ501-1 titanium dioxide-type flux-cored wire under CO₂ gas shielding on low-carbon steel substrates. The study addresses the fundamental challenge in hardfacing technology: balancing deposition efficiency with overlay quality, particularly dilution control.

Core Technical Findings

Process Configuration and Advantages

The dual-wire approach represents a significant departure from conventional single-wire hardfacing. By employing two flux-cored wires simultaneously, the process achieves higher deposition rates while maintaining low dilution rates. The YJ501-1 wire is a TiO₂-type flux-cored wire designed for CO₂ gas shielding, which provides stable arc characteristics and good penetration.

Overlay Characterization

The dual-wire hardfacing produces overlay layers with the following characteristics:

• Structural density: The overlay exhibits a dense, pore-free structure, indicating good arc stability and adequate shielding.
• Performance superiority: The mechanical properties of the overlay are favorable for the intended application.
• Bonding strength: The overlay achieves strong metallurgical bonding with the substrate.
• Dilution control: The dilution rate is notably lower than that achievable with single-wire hardfacing under similar conditions.

The use of a TiO₂-type flux-cored wire is significant because titanium dioxide slag systems provide excellent wetting characteristics and slag fluidity, which promote uniform bead formation and good surface finish. The CO₂ shielding gas provides active shielding that helps maintain arc stability and promotes deeper penetration, which is beneficial for achieving good bonding with the substrate.

Technical Analysis of the Dual-Wire Process

The dual-wire hardfacing process operates on the principle that two independently fed wires create a combined arc that deposits material at a higher rate than a single wire. Several technical aspects are critical to the success of this approach:

Wire Feeding and Arc Interaction

The two wires must be fed at precisely controlled rates to maintain a stable combined arc. If the feeding rates are mismatched, the arc can become unstable, leading to spatter, porosity, or uneven bead formation. The wire separation distance and the angle of approach also influence the arc geometry and penetration profile.

Heat Input Distribution

With dual wires, the total heat input is higher than with a single wire, but the heat input per unit of deposited material is actually lower because more material is deposited per unit time. This is the key to achieving lower dilution rates: the increased deposition rate dilutes the substrate contribution more effectively, even though the total heat input is higher.

Slag Behavior

The TiO₂-type flux in the YJ501-1 wire produces a slag with favorable properties for hardfacing: good fluidity for uniform bead formation, appropriate viscosity for adequate shielding, and sufficient strength for post-weld slag removal. In the dual-wire configuration, the slag from both wires must coexist and flow uniformly across the weld pool, which requires careful parameter optimization.

Engineering Practice Implications

The dual-wire hardfacing technology addresses a critical need in industrial hardfacing: productivity. In many industrial applications, hardfacing is used to restore worn surfaces on large components such as rolling mill rolls, excavator buckets, and mining equipment. The production rate of hardfacing operations is often a limiting factor in repair turnaround times.

The lower dilution rate achieved with dual-wire hardfacing is particularly valuable when using expensive hardfacing alloys. For example, when hardfacing with carbide-containing or cobalt-based alloys, reducing dilution from, say, 30% to 15% can significantly reduce material costs while maintaining overlay performance. The dense structure and strong bonding ensure that the overlay will perform reliably under service conditions.

Potential applications for this technology include:

• Roll hardfacing: Rolling mill backup rolls and work rolls requiring frequent surface restoration.
• Mining equipment: Bucket teeth, blade edges, and wear plates on earth-moving equipment.
• Pump and valve components: Impellers, casings, and valve seats requiring corrosion and erosion resistance.
• Power generation: Boiler tubes, turbine components, and fan blades requiring surface hardening.

Key Questions and Reflections

The study reports favorable results but does not provide detailed quantitative data on deposition rates, dilution percentages, or specific mechanical property values in the abstract. For practical adoption, engineers would need comprehensive process parameter tables including wire feeding speed, travel speed, voltage, wire separation distance, and gas flow rate.

The long-term performance of the dual-wire overlay under actual service conditions is not addressed. Factors such as thermal cycling resistance, fatigue behavior, and resistance to spalling under impact loading are critical for many industrial applications. Additionally, the effect of the dual-wire process on residual stress distribution in the overlay and substrate should be investigated, as high residual stresses can lead to overlay cracking during service.

From a quality control perspective, the dual-wire process introduces additional variables that must be monitored and controlled. The consistency of wire feeding between the two wires, the stability of the combined arc, and the uniformity of the deposited bead all require careful process monitoring. Implementing automated wire feeding with precise rate control and real-time arc monitoring would be essential for production applications.

Study Insights and Conclusions

The dual-wire flux-cored wire hardfacing technology represents a practical advancement in hardfacing productivity. By increasing the deposition rate while simultaneously reducing dilution, this approach addresses two of the most important economic and technical concerns in industrial hardfacing. The use of YJ501-1 TiO₂-type flux-cored wire under CO₂ shielding provides a proven and readily available wire-gas combination. The dense overlay structure and strong metallurgical bonding confirm that the process produces high-quality results. For production engineers evaluating hardfacing process options, this dual-wire approach warrants further investigation, particularly for large-scale applications where productivity is a critical constraint.