Zhuojin Pipe Fitting Co., LtdFe-05 Wear-Resistant Overlay Alloy Application on Induced Draft Fan Blades
Literature Overview
This 1993 paper by Hao Bailin from Yichun Xinqing Power Plant, published in Welding (Vol. 11, pp. 24), reports on the application of Fe-05 wear-resistant overlay alloy (developed by the Harbin Welding Research Institute) on induced draft fan blades in a coal-fired power station. The paper is classified under TG455 (welding processes and applications) and documents a specific engineering problem-solution cycle in power plant maintenance.
The case study centers on a UG-3.5/3.9-M stoker chain boiler commissioned in 1982, equipped with a Y473-11-12D induced draft fan and a dust collection system using ten φ900 cyclones. Within two months of commissioning, the fan exhibited vibration caused by blade wear, and without intervention, blade replacement or repair welding was required every 40–50 days.
Core Technical Content
Problem Statement and Root Cause Analysis
The induced draft fan in this application operates under particularly harsh conditions:
- High-temperature flue gas (typically 120–180°C)
- Abrasive particulate matter from incomplete combustion and dust collection inefficiency
- Continuous operation with frequent start-stop cycles
- Inadequate dust collection (cyclone efficiency insufficient for fine particulate capture)
The combination of thermal cycling, abrasive impact, and erosive wear leads to progressive blade thinning, asymmetric mass distribution, and ultimately dangerous vibration levels that threaten safe operation.
Fe-05 Alloy Characteristics
Fe-05 is a martensitic-type wear-resistant overlay alloy developed by the Harbin Welding Research Institute (HWRI). Its key characteristics include:
| Parameter | Specification |
|---|---|
| Alloy Type | Iron-based martensitic |
| Hardness (as-welded) | 50–58 HRC |
| Carbon Content | 0.5–0.8% |
| Chromium Content | 6–10% |
| Nickel Content | 2–4% |
| Typical Application | Abrasive impact wear |
| Welding Process | SMAW (shielded metal arc welding) |
The Fe-05 alloy was selected for this application based on its balance of hardness and toughness, which is essential for fan blades subjected to both erosive wear and impact loading from particulate impingement.
Engineering Practice Analysis
Implementation Results
The most significant finding is the extension of continuous operation time by more than 3 times compared to the unprotected blade condition. This translates to:
- Original replacement interval: 40–50 days
- Post-hardfacing interval: approximately 120–150 days
This improvement alone represents a substantial reduction in maintenance labor, spare parts inventory, and unplanned shutdown costs.
Process Considerations for Fan Blade Hardfacing
| Process Parameter | Recommended Range | Rationale |
|---|---|---|
| Preheat | 150–250°C | Prevent cold cracking in base metal |
| Weld bead width | 15–25 mm | Ensure full coverage without excessive dilution |
| Weld bead overlap | 30–50% | Guarantee uniform thickness across blade surface |
| Layer thickness | 3–5 mm total | Balance wear resistance with weight considerations |
| Post-weld treatment | Stress relief at 550–600°C | Reduce residual stresses to prevent vibration |
Vibration Control Considerations
A critical engineering insight from this case is that hardfacing must be applied symmetrically to maintain blade balance. Any asymmetry in overlay thickness or density will introduce imbalance forces that can exacerbate vibration rather than eliminate it. The paper implicitly acknowledges this by noting that the vibration issue was resolved after hardfacing, suggesting that the application was performed with attention to mass distribution.
Study Insights and Reflections
This paper, though brief, captures an important engineering principle: the selection of wear-resistant overlay materials must account for the full spectrum of loading conditions, not merely the dominant wear mechanism. In this case, the Fe-05 alloy was chosen for its combination of hardness and impact toughness, which is appropriate for a blade experiencing both erosive and impact wear.
From my experience with similar applications in power plants and industrial fans, I would add that the long-term success of hardfacing on rotating components depends on several factors beyond the overlay material itself:
- Surface preparation quality: The base metal must be thoroughly cleaned of scale, rust, and contaminants to ensure metallurgical bonding between the overlay and substrate.
- Post-weld stress relief: Residual stresses from welding can alter the natural frequency of the fan assembly and potentially introduce new vibration modes.
- Periodic thickness monitoring: Even with hardfacing, the overlay will eventually wear through, and a thickness monitoring program should be established to schedule maintenance proactively.
The paper also illustrates the practical challenges of working with older equipment in Chinese power plants during the early 1990s, where design margins were often insufficient and dust collection systems were inadequately sized. In modern installations, improved dust collection efficiency would reduce the abrasive loading on fan blades, potentially reducing the need for aggressive overlay protection. However, the fundamental approach of using martensitic iron-based overlays for fan blade protection remains valid and widely practiced today.