Carbon Arc Surfacing of Fe610 Wear-Resistant Alloy on Exhaust Fan Blades

Literature Overview

This 1997 publication by Peng Bo from the Harbin Institute of Welding presents an early but highly practical application of Fe610 wear-resistant alloy powder block in carbon arc surfacing of exhaust fan blades. The work addresses a persistent operational challenge in thermal power plants and coal-handling facilities, where exhaust fan blades suffer from severe abrasive and erosive wear due to the continuous impact of fly ash-laden gas streams. The reported 3 to 5 times improvement in blade service life represents a significant operational gain, particularly when considering the frequency of blade replacement and the associated downtime costs in large-scale power generation systems.

Core Technical Approach

The carbon arc surfacing (CAAW) process employed here utilizes a carbon electrode to melt both the Fe610 alloy powder block and the base material simultaneously, achieving metallurgical bonding through a dilution-controlled melt pool. The powder block configuration allows for precise control over the surfacing layer composition and thickness, which is critical for achieving uniform wear resistance across the blade surface.

The Fe610 alloy belongs to the high-carbon martensitic wear-resistant steel family, characterized by elevated carbon content (typically 2.5–3.5 wt%) and high chromium content (typically 12–15 wt%). These compositional features produce a microstructure dominated by hard carbides (primarily M7C3 type) dispersed in a martensitic matrix, which provides excellent resistance to abrasive and erosive wear. The high hardness of the as-deposited layer typically reaches 58–62 HRC, significantly exceeding the base material hardness of 20–28 HRC.

Process Analysis and Key Considerations

Carbon arc surfacing is a robust and economical process well-suited for field repair and large-area surfacing applications. However, several technical challenges must be addressed to achieve the reported performance:

1. Dilution control: The carbon arc process inherently produces higher dilution rates (typically 30–60%) compared to powder surfacing processes such as flame spraying or plasma arc surfacing. Excessive dilution reduces the carbide volume fraction in the surfacing layer, degrading wear resistance. The powder block configuration partially mitigates this by providing a concentrated source of alloying elements near the melt pool.
2. Residual stress management: The rapid cooling rates associated with CAAW on thin-walled blade geometries can generate significant residual tensile stresses at the fusion boundary. These stresses may contribute to spalling or cracking of the surfacing layer under cyclic loading conditions typical of fan blade operation.
3. Layer uniformity: Maintaining consistent surfacing thickness across the blade surface requires skilled operator technique and appropriate fixture design. Local thin spots become preferential wear locations and can initiate premature failure.

Engineering Practice Integration

From a practical standpoint, this technology finds direct application in the maintenance of large centrifugal and axial flow fans used in boiler air supply systems, induced draft fans, and dust collection systems. The blades in these applications operate at rotational speeds of 600–1500 rpm and are exposed to fly ash particles with median diameters of 20–100 μm traveling at gas velocities of 15–25 m/s. The erosive wear mechanism is primarily cutting wear, where hard ash particles micro-cut the blade surface, removing material in a ploughing action.

The selection of Fe610 over alternative wear-resistant alloys such as Fe609 or Fe612 should be guided by the specific wear mechanism and service temperature. Fe610 excels in abrasive and erosive wear scenarios but may not be optimal for impact wear or high-temperature oxidation environments. For applications where the blade surface temperature exceeds 300°C, post-weld stress relief at 550–600°C is advisable to reduce the risk of temper embrittlement in the base material heat-affected zone.

Study Insights

This work exemplifies the pragmatic approach of Chinese welding research institutions in the 1990s, focusing on solving immediate industrial problems with available materials and processes. The Fe610 carbon arc surfacing solution represents a cost-effective alternative to blade replacement or more sophisticated thermal spray coatings. However, the relatively high dilution inherent to CAAW limits the maximum achievable hardness and wear resistance compared to lower-dilution processes. Modern alternatives such as plasma arc surfacing with Fe610 powder or HVOF spraying of hardfacing alloys could potentially offer superior performance with thinner, more precisely controlled layers. The enduring value of this work lies in demonstrating that even relatively simple surfacing technologies can deliver substantial operational benefits when properly applied to the right service conditions.