Research and Development of High-Temperature Wear-Resistant Surfacing Electrode

Literature Overview

The paper by Meng Gongge, Lu Yunlong, and Li Dan from Harbin University of Science and Technology, published in the journal Welding (2005, Vol. 4, pp. 27-29), reports on the development of a high-temperature wear-resistant surfacing electrode containing boron and multiple alloying elements. The authors systematically investigated the microstructure, hardness, and wear resistance of the deposited metal at both ambient and elevated temperatures, benchmarking their results against the internationally recognized Castolin 6715 electrode.

Core Technical Content

The primary objective of this research was to address the critical challenge of component degradation under combined high-temperature and abrasive conditions, a common failure mode in power generation, cement kilns, and thermal processing equipment. The authors designed an electrode formulation enriched with boron and additional alloying elements to achieve a hypereutectic microstructure in the deposited metal. This microstructural strategy is fundamental because hypereutectic compositions promote the formation of primary carbide particles (predominantly Cr7C3 and B-containing carbides) that provide superior resistance to abrasive and erosive wear mechanisms.

Microstructural Characteristics

The deposited metal was confirmed to exhibit a hypereutectic organization through metallographic examination. This means the carbon content in the weld metal exceeded the eutectic point, resulting in the precipitation of free carbide particles during solidification. The presence of boron in the system plays a dual role: it refines the grain structure and contributes to the formation of hard boride phases that enhance both room-temperature and elevated-temperature hardness.

Performance Comparison

The most remarkable finding is the retention of hardness at 800°C, where the developed electrode maintained HV297.3. This level of hardness retention at such elevated temperatures is technically challenging because most carbide phases undergo softening and dissolution above 700°C. The presence of boron-stabilized carbides appears to contribute significantly to this high-temperature hardness retention.

Engineering Practice Integration

From an engineering perspective, this electrode is particularly suitable for components operating in environments where temperatures fluctuate between 500°C and 800°C, such as:

• Rotary kiln linings and trunnion rollers in cement plants
• Hot gas ducts and cyclone separators in coal-fired power stations
• Burner tips and refractory contact surfaces in metallurgical furnaces
• High-temperature slide valves and actuator components

The SMAW (Shielded Metal Arc Welding) process using this electrode offers practical advantages for field repair applications where equipment shutdown windows are limited. The hypereutectic structure requires careful control of welding parameters to avoid excessive dilution from the base metal, which would shift the composition toward the eutectic or hypoeutectic regime and compromise hardness.

Key Technical Insights and Reflections

The development of this electrode reflects a systematic approach to surfacing alloy design: identifying the target operating temperature, selecting alloying elements that stabilize hard phases at those temperatures, and verifying performance through comparative testing. The use of boron as a key alloying element is particularly noteworthy because boron-containing carbides (such as Fe2B and FeB) exhibit high melting points and exceptional hardness retention above 600°C.

However, several practical considerations must be addressed when deploying such electrodes in production:

1. Boron is highly susceptible to oxidation during arc welding, requiring careful control of arc length and travel speed to minimize atmospheric pickup.
2. The hypereutectic structure may exhibit reduced ductility, necessitating appropriate interpass temperature control and post-weld heat treatment to manage residual stresses.
3. Dilution from low-carbon steel base metals can significantly alter the weld metal composition, potentially requiring a multi-pass approach with a transition layer.

Study Implications and Outlook

This research demonstrates that the strategic incorporation of boron into high-temperature surfacing alloys can substantially improve hardness retention at elevated temperatures. The comparison with Castolin 6715 establishes a credible benchmark, showing that domestic electrode development can achieve performance parity or superiority with internationally recognized products. For engineers involved in equipment maintenance and surface engineering, this work provides a valuable reference for selecting appropriate surfacing materials for high-temperature wear applications. The hypereutectic design philosophy can be extended to other alloy systems (such as Ni-Cr-B or Co-Cr-B) for even more demanding service conditions, opening pathways for further alloy optimization and process refinement.