Wear Resistance Performance of Sintered Wear-Resistant and Heat-Resistant Overlay Welding Electrodes

Literature Overview

This paper by Xue Wentao, Ma Jianghong, Ji Guojuan, Wang Lei, Tian Ye, Zhang Deming, Yang Xiaojian, and Ren Xianjing from the Beijing Research Institute of Mining and Metallurgy, published in Nonferrous Metals (Metallurgy Section) (2008, Issue S1), presents research on the wear resistance performance of sintered-type wear-resistant and heat-resistant overlay welding electrodes under high-speed friction wear conditions.

Core Technical Content

The study focuses on a sintered-type welding electrode designed for applications combining both wear resistance and heat resistance. The electrode is manufactured through a powder metallurgy approach — specifically, the sintering method — which allows for precise control over the alloy composition and microstructure of the deposited weld metal.

Manufacturing Approach

The sintered electrode approach involves:

1. Powder blending — Mixing of alloy powders (likely Ni-Co-Cr-B-C system based on related publications from the same research group) in specific proportions.
2. Forming — Compacting the powder blend into electrode shape.
3. Sintering — Thermal treatment to bond particles while preserving the designed microstructure.
4. Coating — Application of flux coating for arc stabilization and weld protection.

Performance Characteristics

The study demonstrates that the sintered electrode maintains good wear resistance even under high-speed friction conditions, which is a significant advantage over conventional cast or wrought overlay electrodes that may suffer from microstructural degradation at elevated temperatures generated by friction.

Technical Analysis

Advantages of Sintered Electrodes

The sintered manufacturing route offers several distinct advantages for overlay welding applications:

• Homogeneous composition — Powder blending ensures uniform distribution of alloying elements throughout the electrode, resulting in consistent weld metal chemistry.
• Controlled microstructure — The sintering process can be tuned to produce specific grain sizes and phase distributions.
• Customizable alloy design — Unlike cast electrodes limited by fluidity and shrinkage considerations, sintered electrodes can incorporate brittle intermetallic phases (such as borides and carbides) that would be difficult to achieve in cast form.
• Reduced segregation — Powder metallurgy minimizes macrosegregation and microsegregation inherent in casting processes.

High-Speed Friction Wear Mechanisms

In high-speed friction wear conditions, the following mechanisms typically dominate:

1. Adhesive wear — Material transfer between contacting surfaces due to localized cold welding and subsequent shearing.
2. Abrasive wear — Hard particles or asperities ploughing through the softer surface.
3. Thermal degradation — Softening of the surface layer due to frictional heating, reducing hardness and accelerating wear.
4. Oxidative wear — Formation of oxide layers that may be protective or detrimental depending on the alloy system.

The Ni-Co-Cr-B-C system is particularly suited for high-speed friction wear because:

• The FCC matrix (Ni-Co solid solution) maintains good toughness even at elevated temperatures
• M23(C,B)6 carbides provide wear resistance and thermal stability
• The boride phases contribute additional hardness without excessive brittleness

Engineering Practice Integration

Application Scenarios

This type of sintered overlay electrode is particularly suitable for:

• Mining equipment — Crusher components, conveyor rollers, and feeders operating at high speeds with abrasive materials
• Cement industry — Mill liners, fan blades, and duct linings exposed to high-temperature abrasive gases
• Power generation — Turbine components and heat exchanger surfaces experiencing thermal cycling and erosion
• Steel pipe manufacturing — Pipe mill rollers, bending mandrels, and forming tools that experience high-speed contact with hot steel pipe

Quality Control Considerations

When applying sintered overlay electrodes in production, the following quality control measures should be implemented:

1. Pre-weld inspection — Verify base metal cleanliness, fit-up, and preheating requirements.
2. Welding parameter control — Maintain consistent arc voltage, current, and travel speed to ensure uniform deposition.
3. Post-weld hardness testing — Verify hardness profile meets specification (typically 45–55 HRC for Ni-based systems).
4. Microstructural examination — Periodic metallographic checks to confirm expected phase distribution.
5. Wear testing — Periodic validation using standardized wear tests (pin-on-disk, ball-on-disk) to confirm performance consistency.

Key Questions and Reflections

The study confirms the viability of sintered electrodes for demanding high-speed friction applications, but several questions remain for practical implementation:

• Cost-effectiveness — Sintered electrodes typically carry a premium over conventional electrodes. The engineer must evaluate whether the extended service life justifies the higher material cost.
• Weldability — Sintered electrodes may exhibit different welding characteristics (arc stability, spatter rate, slag formation) compared to conventional electrodes. Welder training and parameter optimization are essential.
• Scalability — Can sintered electrode production be scaled to meet large-volume industrial demand while maintaining consistent quality?

Study Insights

This research contributes to the growing body of knowledge on powder metallurgy-based welding consumables. The key takeaway for engineers is that the manufacturing route of the welding electrode itself significantly influences the final weld deposit properties. When selecting overlay electrodes for critical applications, engineers should consider not only the nominal alloy composition but also the manufacturing process (cast, wrought, or sintered) and its implications for microstructure and performance.