Research on Iron-Based High-Temperature Wear-Resistant Overlay Welding Electrodes

Literature Overview

The paper by Liu Zhengjun, Ji Jie, and Hao Xuefeng (1995), published in the Journal of Shenyang University of Technology (Vol. 17, No. 3, pp. 35-38), reports on the development and characterization of two iron-based alloy systems for high-temperature wear-resistant overlay welding electrodes. This research is particularly relevant to engineers working in power generation, mining, and heavy industry where components are subjected to simultaneous wear and elevated temperature exposure. The study represents an important contribution to the field of welding consumables development in China during a period of rapid industrialization.

Alloy System Design and Microstructural Analysis

The two alloy systems investigated were:

The microstructural analysis reveals fundamental differences in the strengthening mechanisms between the two systems. System 1 relies on a combination of solid solution strengthening (from Ni and Cr in austenite), precipitation hardening (from Nb and V carbides), and dispersion strengthening (from eutectic carbides). The skeletal eutectic carbide network provides a continuous hard phase framework that resists abrasive wear, while the granular carbides offer additional resistance to erosive wear.

System 2, by contrast, achieves high-temperature hardness through martensitic transformation of the matrix combined with hard phase dispersion. The acicular martensite provides high room-temperature hardness, while the blocky hard phases (likely complex carbides containing W and Mo) maintain hardness at elevated temperatures through their high thermal stability.

Welding Process Considerations

The development of iron-based overlay welding electrodes for high-temperature service requires careful attention to several process parameters:

1. Electrode coating composition: The coating must provide sufficient alloying element transfer to the weld metal while maintaining good arc stability and slag characteristics. The flux composition must be designed to promote the desired microstructure and minimize porosity.
2. Deposition efficiency: Iron-based electrodes typically achieve 60-75% deposition efficiency, which is acceptable for overlay applications where the focus is on surface performance rather than joint strength.
3. Heat input control: The welding heat input must be controlled to ensure complete melting of the overlay material while avoiding excessive dilution from the base metal. A typical heat input range of 0.8-1.5 kJ/mm is recommended for overlay applications.
4. Interpass temperature: For high-alloy overlay electrodes, interpass temperature control is critical to prevent excessive grain growth and to maintain the desired microstructure. An interpass temperature of 150-250°C is generally recommended.

High-Temperature Wear Mechanisms and Material Selection

The selection between the two alloy systems depends on the specific wear mechanism and temperature range:

The Cr-Ni-B-W-V-Nb system is particularly effective in abrasive and erosive wear environments due to the continuous carbide network that provides excellent resistance to material removal by hard particles. The Cr-B-W-Mo-Nb system is more suitable for sliding wear and high-temperature oxidation environments due to the thermal stability of the blocky hard phases and the oxide-forming capability of Cr and Mo.

Engineering Practice Implications

This research has direct applicability to several engineering scenarios:

• Boiler tube repair: In coal-fired power plants, boiler tubes exposed to high-temperature flue gas and ash erosion can be effectively repaired by overlay welding with iron-based high-temperature wear-resistant electrodes. The overlay thickness of 2-4 mm is typically sufficient to restore the tube to service life.
• Mining equipment: Crusher components, conveyor rollers, and shovel teeth exposed to abrasive materials at elevated temperatures can benefit from iron-based overlay welding. The overlay provides a hard, wear-resistant surface while maintaining the structural integrity of the base material.
• Industrial furnace components: Refractory-lined furnace components and hot gas ducts can be protected by iron-based overlay welding, extending their service life significantly.

Study Insights and Reflections

This research demonstrates the power of alloy design in tailoring overlay welding materials to specific service environments. The two alloy systems represent fundamentally different strengthening strategies—one based on austenitic matrix with eutectic carbides, and the other on martensitic matrix with blocky hard phases. Understanding these microstructural differences is essential for engineers to make informed material selection decisions. In my experience, the most common failure mode for overlay-welded components is not wear but delamination at the fusion boundary, which is why proper base metal preparation and welding procedure qualification are as important as the overlay material selection. The research also highlights the importance of Nb as a microalloying element in stabilizing fine carbides at high temperatures, a finding that has been validated in subsequent research and industrial applications.