Zhuojin Pipe Fitting Co., LtdEffect of Feldspar Addition on Microstructure and Wear Resistance of Arc Overlay Welding Alloy
Literature Overview
Published in Arms Materials and Science & Engineering (Vol. 47, No. 6, 2024, pp. 53-58) by Liu Chao and Gong Jianxun from Xiangtan University, this study investigates the influence of feldspar as an active flux on the microstructure and wear resistance of arc overlay welding deposits. The research employs a side-adding method to introduce feldspar-containing active layers into the overlay welding process, using high-speed camera analysis, X-ray diffraction, scanning electron microscopy with EDS, and wear testing to characterize the effects. Funded by the Hunan Provincial Natural Science Foundation (2021JJ30669), this work represents a cost-effective approach to optimizing overlay welding deposits through flux engineering.
Experimental Design and Methodology
The experimental approach is noteworthy for its systematic investigation of the relationship between active flux composition and overlay deposit properties:
| Parameter | Description |
|---|---|
| Active agent | Feldspar (KAlSi3O8) containing active layer blocks |
| Addition method | Side-adding via active layer blocks |
| Welding process | Open-arc overlay welding (SMAW/GMAW variant) |
| Filler materials | Composite powder particles and solid wire |
| Characterization | XRD, SEM-EDS, high-speed arc imaging, pin-on-disk wear test |
| Key variable | Feldspar content in the active layer |
The side-adding technique is particularly clever because it allows independent control of the flux composition without modifying the filler wire or powder composition. This approach mimics the function of traditional flux-cored welding consumables while maintaining the flexibility of separate filler material selection.
Arc Behavior Analysis
One of the most significant findings concerns the dramatic change in arc morphology induced by feldspar addition:
- Without active layer: The arc exhibits a classic bell-shaped (dome-shaped) configuration with concentrated energy density.
- With feldspar active layer: The arc expands into a hemispherical shape, significantly increasing the arc coverage area.
This arc expansion has direct consequences for the overlay welding process:
- Increased powder particle deposition rate: The expanded arc envelope captures more powder particles from the composite filler system, increasing the effective deposition of the wear-resistant composite material.
- Enhanced preheating of the solid wire: The broader arc distribution provides more uniform and intense preheating to the solid wire, improving its melting efficiency.
- Modified heat input distribution: The hemispherical arc creates a wider heat-affected zone, which affects the cooling rate and consequently the solidification microstructure of the deposit.
Microstructural Evolution and Wear Mechanism
The study reveals a clear relationship between feldspar content, microstructure, and wear resistance:
| Feldspar Content | Primary M7C3 Morphology | Wear Resistance | Arc Behavior |
|---|---|---|---|
| No addition | Fine strip-like | Baseline | Bell-shaped, concentrated |
| Optimal addition | Plate-like (transformed) | Significantly increased | Hemispherical, expanded |
| Excessive addition | Reduced quantity | Decreased | Over-expanded, excessive wire melting |
The transformation of primary M7C3 carbide from fine strip-like to plate-like morphology is metallurgically significant. Plate-like M7C3 carbides provide superior wear resistance through several mechanisms:
- Increased volume fraction: The morphology change is associated with a higher overall carbide volume fraction in the deposit.
- Improved load-bearing capacity: Plate-like carbides distribute applied loads more effectively than thin strip-like carbides.
- Enhanced ploughing resistance: The broader cross-section of plate-like carbides provides greater resistance to abrasive wear mechanisms.
The optimal feldspar content represents a critical balance point where the arc expansion maximizes powder particle utilization without causing excessive wire melting that would dilute the composite composition.
Engineering Practice Integration
From a practical standpoint, this research offers several actionable insights:
- Cost reduction: Feldspar is an abundant, low-cost mineral that can significantly improve overlay welding performance without requiring expensive alloying additions to the filler material.
- Process optimization: The side-adding technique can be easily implemented in existing overlay welding setups with minimal equipment modification.
- Wear life extension: The improved wear resistance translates directly to longer service intervals for components such as mining equipment, cement mill liners, and industrial wear plates.
Key Technical Considerations
Several important engineering considerations emerge from this study:
- Reproducibility of active layer application: The uniformity of the feldspar active layer on the block surface directly affects process consistency and must be controlled in production.
- Interaction with base material: The expanded arc and increased heat input may increase dilution from the base material, potentially affecting the final composition of the overlay.
- Residual stress implications: The wider heat-affected zone associated with the hemispherical arc may influence residual stress patterns in the overlay and base material.
- Scale-up considerations: While the laboratory-scale investigation demonstrates clear benefits, field application requires verification of the optimal feldspar content under actual production welding conditions with variable heat input and deposition rates.
Study Insights
This research demonstrates that flux engineering remains a powerful and underutilized tool for optimizing overlay welding performance. The elegant simplicity of using a common mineral as an active agent to fundamentally alter arc behavior and deposit microstructure is reminiscent of classical welding metallurgy principles applied with modern characterization techniques. The finding that arc morphology directly controls powder particle utilization efficiency opens new avenues for process optimization in composite overlay welding systems, particularly for applications where high deposition rates of wear-resistant material are desired.