Zhuojin Pipe Fitting Co., LtdMicrostructure and Properties of Wear-Resistant Electrode Overlay for Hydraulic Gate Repair
Literature Overview
This study, published in Materials in Mechanical Engineering (2025, Vol. 49, No. 11) by Zhu Sisi and colleagues from China Yangtze Power Corporation and Hohai University, addresses a critical engineering challenge: the additive repair of hydraulic gates using a specially designed wear-resistant electrode. The research is funded by the National Engineering Research Center for Efficient Water Resources Utilization and Engineering Safety, underscoring its relevance to major hydropower infrastructure maintenance.
Electrode Design and Composition
The wear-resistant electrode was designed with a comprehensive flux composition and a 0Cr13 stainless steel core wire:
| Component | Function |
|---|---|
| Reduced iron powder | Iron reinforcement, dilution control |
| Attapulgite ore | Viscosity control, arc stability |
| Potash feldspar | Flux agent, slag formation |
| Water glass | Binder |
| Rutile | Arc stabilizer, hydrogen control |
| Fluorite | Deoxidizer, slag fluidity |
| Manganese powder | Alloy reinforcement, hardenability |
| Cellulose | Arc regulation, gas shielding |
| Al-Si alloy | Deoxidizer, grain refinement |
| Silicon-iron alloy | Silicon reinforcement |
| Rare earth silicon-iron | Grain refinement, inclusion modification |
The 0Cr13 core wire selection is significant—it provides the base iron content while contributing chromium for martensitic transformation capability in the weld metal.
Microstructural Analysis
The overlay deposit produced by three-layer, multi-pass manual arc welding (SMAW) underwater on Q235 steel substrate exhibits:
- Primary phase: Lath martensite growing along the temperature gradient direction, forming columnar crystals
- Secondary phase: Small volume fraction of δ-ferrite
- No cracking defects observed in the overlay
The martensite grain size is smaller and the martensite volume fraction is higher compared to ordinary electrode overlay deposits. The δ-ferrite content is correspondingly lower. This microstructural refinement is attributed to the synergistic effect of manganese and silicon alloying combined with rare earth grain refinement from the Al-Si and rare earth silicon-iron additions.
Wear Performance Comparison
| Property | Wear-Resistant Electrode | Ordinary Electrode |
|---|---|---|
| Microstructure | Fine lath martensite + minimal δ-ferrite | Coarser martensite + more δ-ferrite |
| Microhardness | Higher | Lower |
| Friction coefficient | Lower | Higher |
| Wear rate | Lower | Higher |
| Wear mechanism | Mild abrasive wear | More severe abrasive wear |
The wear surface of the wear-resistant electrode overlay shows shallow, uniformly distributed ploughing grooves with localized minor spalling, debris, and micro-cracks—characteristic of mild abrasive wear. This is a favorable wear regime indicating that the material is operating below its critical wear threshold.
Engineering Practice Considerations
The underwater welding application adds complexity that deserves emphasis:
- Hydrogen control: The rutile and cellulose components in the flux help manage hydrogen pickup in the underwater environment, which is critical for preventing cold cracking in martensitic weld metal
- Arc stability: Attapulgite and water glass contribute to arc stability under water pressure conditions
- Multi-pass strategy: The three-layer, multi-pass approach allows controlled heat input and proper dilution management, which is essential for achieving the desired martensitic microstructure without excessive substrate dilution
FMEA Perspective on Underwater Overlay Welding
Applying a Failure Modes and Effects Analysis framework to this application:
| Potential Failure Mode | Cause | Mitigation |
|---|---|---|
| Hydrogen cracking | Excessive hydrogen pickup | Rutile flux, controlled arc length |
| Excessive dilution | High heat input | Multi-pass with controlled travel speed |
| Incomplete fusion | Water interference with arc | Proper flux design for arc confinement |
| Porosity | Gas entrapment | Cellulose arc regulation, proper shielding |
| Hardness non-uniformity | Inconsistent cooling rate | Layer thickness control |
Study Insights
The key insight from this work is that electrode composition engineering—particularly the inclusion of rare earth elements and strategic alloy additions—can substantially improve overlay performance even under the challenging conditions of underwater welding. The transition from a wear regime dominated by severe abrasive wear to mild abrasive wear represents a significant service life extension for hydraulic gates. For hydropower engineers responsible for gate maintenance, this study provides a validated electrode specification that can be directly implemented in repair programs, reducing unplanned downtime and extending inspection intervals between maintenance cycles.