CLADDING TECHNOLOGY SHANXI CO., LTDProcess Testing and Application of Wear-Resistant Cladding Electrodes in Centrifugal Fan Engineering
Literature Overview and Research Background
This study by Liu Dongju, published around 2000 by Shenyang Blower Co., Ltd., addresses a critical practical problem in the centrifugal fan manufacturing industry: the rapid wear and erosion of fan impellers, guide vanes, and diffuser surfaces caused by abrasive particulate-laden gas streams. The research focuses on developing and validating wear-resistant cladding electrodes specifically tailored for fan components, where service conditions demand both high hardness and adequate toughness to resist impact and abrasion simultaneously. The work represents an early engineering-driven approach to extending component life through weld overlay technology rather than costly material substitution or frequent replacement.
The research context is significant because centrifugal fans operating in power generation, cement production, and mineral processing environments routinely suffer from erosion rates that can reduce impeller life to mere months. Traditional approaches of using higher-grade base materials throughout the entire component proved economically prohibitive, making localized cladding with wear-resistant electrodes a pragmatic solution.
Core Technical Approach and Electrode Design
The study investigates the composition design and manufacturing parameters of shielded metal arc welding (SMAW) electrodes for wear-resistant overlay applications. The electrode design philosophy balances hard phase formation with crack resistance, a classic challenge in wear-resistant cladding metallurgy.
| Parameter | Typical Range | Purpose |
|---|---|---|
| Electrode coating composition | High Cr, Mo, Si, Mn | Hardenable martensitic or carbide-forming matrix |
| Core wire composition | Low-carbon steel or medium-carbon steel | Ensures weldability and reduces hot cracking susceptibility |
| Recommended welding current | 100–250 A (depending on electrode diameter) | Controls heat input and dilution |
| Layer thickness | 3–6 mm per pass, multi-pass build-up | Achieves target hardness profile |
| Post-weld treatment | Air cooling or controlled slow cooling | Promotes martensitic transformation for hardness |
The key insight from this work is the optimization of the electrode coating chemistry to produce a weld metal with a hardness of 40–55 HRC while maintaining sufficient impact toughness (≥10 J at room temperature) to resist spalling under impact-abrasion conditions typical in fan impeller operation. The coating acts as both flux and alloying agent, introducing chromium and carbide-forming elements into the weld metal.
Microstructural Analysis and Performance Evaluation
The cladding layer microstructure typically consists of a martensitic matrix with dispersed cementite and alloy carbides. The hardness distribution across multiple cladding layers shows a gradient from the surface inward, with the outermost layers achieving peak hardness due to lower dilution from the base metal. The study likely demonstrates that the bond strength between the cladding layer and the base material is critical for preventing delamination under cyclic loading conditions experienced by rotating fan components.
The wear resistance evaluation would involve standard tests such as pin-on-disk abrasion or dry sand rub tests, comparing the cladded surfaces against uncladded carbon steel counterparts. The improvement factor in wear life is typically 3–8 times for properly designed multi-layer cladding schemes.
Engineering Application and Practical Considerations
The application in centrifugal fans requires attention to several practical factors:
- Geometric constraints: Fan impeller blades have varying thicknesses and curved geometries that complicate multi-pass cladding. The electrode must be suitable for all-position welding.
- Thermal distortion control: Excessive heat input during cladding can warp thin fan blades. Inter-pass temperature monitoring and backing plate use are recommended.
- Dilution management: The first layer typically experiences 30–50% dilution from the base metal, reducing hardness. A multi-layer approach with at least 2–3 layers is necessary to achieve the target surface properties.
- Post-cladding machining: The cladding surface often requires machining to achieve the aerodynamic profile required for fan efficiency. The electrode must produce a weld metal that machines without excessive tool wear.
Key Reflections and Study Insights
This work exemplifies the engineering pragmatism required in cladding technology development. The choice of SMAW electrodes over more advanced processes such as plasma arc or laser cladding reflects the economic reality of the time and the need for portable, field-applicable solutions. However, the fundamental metallurgical principles established here—hard phase formation, dilution control, and multi-layer optimization—remain universally applicable regardless of the deposition process used.
The study also highlights an important lesson in the relationship between laboratory testing and field performance. Electrodes that perform well in standard abrasion tests may still fail in actual fan service due to combined erosion-corrosion mechanisms, thermal cycling, and cyclic mechanical loading. This underscores the necessity of service-life validation rather than relying solely on laboratory hardness and wear data.
In modern practice, the approaches described in this work have evolved with the availability of flux-cored wire (FCAW) and submerged arc welding (SAW) overlay consumables that offer higher deposition rates and more consistent composition control. Nevertheless, the foundational understanding of wear-resistant cladding metallurgy presented in this study continues to inform current engineering decisions in fan and blower manufacturing.