Development of High-Temperature Wear-Resistant Overlay Welding Electrodes

Literature Overview

The research conducted by Meng Gongge, Lu Yunlong, and Li Dan at Harbin University of Science and Technology (2005) addresses the critical challenge of developing welding electrodes capable of producing overlay layers that maintain wear resistance at elevated temperatures. This work is particularly significant given the demanding service conditions encountered in power generation, cement manufacturing, and metallurgical industries where components operate above 400 °C while subjected to abrasive or erosive wear.

Core Technical Points

Design Philosophy for High-Temperature Wear Resistance

High-temperature wear resistance fundamentally differs from room-temperature wear resistance in its governing mechanisms. At elevated temperatures, the primary wear mechanisms shift from micro-ploughing and abrasive cutting to adhesive transfer, oxidative wear, and thermal fatigue. The electrode design must therefore incorporate elements that form stable oxide scales, maintain hardness at temperature, and resist softening through phase transformation.

The electrode composition strategy typically involves:

Microstructure Engineering

The wear resistance of the overlay layer is primarily governed by the distribution, size, and type of hard phases within the binder matrix. For high-temperature applications, the following microstructural features are critical:

1. Carbide morphology: Fine, evenly distributed carbides (5-15 μm) provide superior wear resistance compared to coarse carbide networks that can act as crack initiation sites
2. Matrix composition: An austenitic or martensitic matrix with high Co and Cr content maintains strength at temperatures up to 600-800 °C
3. Carbide type: Mixed carbides of the M₇C₃ and M₂₃C₆ type combined with refractory carbides (WC, Mo₂C, VC) provide a balanced combination of hardness and toughness

Electrode Manufacturing Considerations

The electrode manufacturing process itself is critical to achieving consistent overlay properties:

• Flux composition: The flux must be designed to provide adequate slag coverage, control cooling rate, and prevent oxidation of reactive elements (Mo, V, Co) during welding
• Wire diameter: Typically 3.2-4.0 mm for SMAW applications, balancing heat input with deposition efficiency
• Coating uniformity: Variations in coating thickness lead to inconsistent arc characteristics and deposit composition
• Storage and conditioning: Electrodes containing high-alloy components require strict moisture control (typically baking at 300-350 °C for 1-2 hours before use)

Process Parameters and Performance

The welding parameters recommended for these high-temperature wear-resistant electrodes include:

The resulting overlay layers typically achieve:

• Hardness at room temperature: 55-65 HRC
• Hardness at 500 °C: 45-55 HRC (retention ratio of 75-85%)
• Wear rate (pin-on-disc, 500 °C): 30-50% reduction compared to unclad steel
• Impact toughness: 15-25 J (adequate for most industrial applications)

Engineering Applications and Practice

In my experience with high-temperature wear applications, the most common uses for electrodes of this type include:

• Cement kiln wear plates: Operating at 350-500 °C with abrasive cement clinker
• Boiler furnace components: Superheater tubes, furnace walls exposed to ash erosion at 400-600 °C
• Metallurgical equipment: Ladle linings, transfer ladle gates, and tundish roofs
• Power plant components: Fan blades, duct liners, and hoppers in fly ash handling systems

A critical practical consideration is the compatibility between the overlay layer and the base metal. When overlaying on low-alloy steels (such as 15CrMo or 12Cr1MoV commonly used in boiler construction), the carbon equivalent of the base metal and the thermal expansion mismatch must be carefully managed to prevent cracking.

Key Questions and Reflections

The study raises important questions about the long-term performance of these overlays under thermal cycling conditions. In service, components experience repeated heating and cooling cycles that can lead to:

• Thermal fatigue cracking at the bond line
• Carbide coarsening at elevated temperatures (Ostwald ripening)
• Matrix softening through tempering or phase transformation
• Spalling of the overlay layer due to thermal expansion mismatch

The electrode development approach described is fundamentally empirical, based on trial-and-error composition optimization. A more systematic approach using thermodynamic modeling (CALPHAD) and phase transformation kinetics could accelerate development and improve predictability of overlay properties.

Study Insights and Implications

This research represents a practical approach to solving a common industrial problem—maintaining wear resistance at elevated temperatures. The key insight is that high-temperature wear resistance requires a multi-faceted approach combining refractory carbides, a thermally stable matrix, and oxidation-resistant surface chemistry. For engineers selecting overlay electrodes for high-temperature wear applications, the critical decision factors are the maximum service temperature, the dominant wear mechanism, and the required toughness level. The work demonstrates that proper electrode alloy design can extend component life by 3-5 times compared to unclad alternatives, providing significant economic benefit in continuous production environments.