CLADDING TECHNOLOGY SHANXI CO., LTDSpecial Wear-Resistant Overlay Welding Electrodes
Literature Overview
This technical article by Sun Weijun (2002) from Beijing Tiangong Yu Industry and Trade Company discusses the development and application of special wear-resistant overlay welding electrodes. Published in the journal New Technology and New Process, this work addresses the design philosophy, composition optimization, and practical application of electrode-type consumables for producing hardfacing overlays on industrial components subjected to severe abrasive and adhesive wear conditions.
Core Technical Points
Wear-resistant overlay welding electrodes are designed to deposit hard, wear-resistant surfaces on base materials that are susceptible to material loss through abrasion, impact, or corrosion-abrasion. The wear resistance of the overlay layer is primarily determined by the hardness and microstructure of the deposited metal, which in turn depends on the alloy composition of the electrode and the cooling conditions during solidification.
Classification of Wear-Resistant Overlay Electrodes
| Type | Hardness (HRC) | Microstructure | Application |
|---|---|---|---|
| Cast Iron Type | 40-50 | Pearlite + carbides | Moderate abrasion |
| Martensitic Type | 50-55 | Hard martensite | Heavy abrasion, impact |
| Carbide Type | 60-70 | Cementite (Fe₃C) | Severe abrasion |
| Hardfacing Type | 55-65 | Chromium carbides | High-temperature wear |
| Composite Type | 50-65 | Mixed carbides | Mixed wear conditions |
Typical Electrode Compositions
| Electrode Type | Key Alloying Elements | Typical Composition |
|---|---|---|
| High Carbon Martensitic | C 2.5-3.5%, Cr 5-8% | Fe-balanced |
| Chromium Carbide Type | C 3.5-5.0%, Cr 20-30% | Fe-balanced |
| Nickel Hardfacing | Ni 75-90%, Cr 5-10%, Mo 5-8% | Ni-balanced |
| Cobalt Hardfacing | Co 50-65%, Cr 15-25%, W 10-20% | Co-balanced |
FMEA Analysis of Overlay Defects
| Defect | Cause | Countermeasure |
|---|---|---|
| Cracking | High carbon equivalent, rapid cooling | Preheat, control interpass temp |
| Excessive Dilution | High heat input, thin overlay | Multiple thin passes, lower current |
| Porosity | Moist flux coating, contaminated base | Dry electrodes, clean substrate |
| Hardness Below Spec | Excessive dilution, improper heat treatment | Increase passes, post-weld treatment |
| Spalling | Poor bond strength, thermal mismatch | Surface preparation, proper preheat |
Process Optimization
The performance of wear-resistant overlay electrodes is influenced by several factors:
- Heat Input Control: Higher heat input leads to greater dilution, which reduces the hardness of the overlay layer by incorporating softer base metal into the deposit. For carbide-type electrodes, maintaining heat input below 1.5 kJ/mm ensures adequate hardness retention.
- Overlay Thickness: A minimum overlay thickness of 2-3 mm is typically required to achieve the full hardness potential of the electrode composition. Thinner overlays suffer from excessive dilution effects.
- Pass Configuration: Multi-pass overlay with thin individual passes (1-2 mm per pass) provides better hardness uniformity and reduces cracking risk. The last pass is critical for achieving the target surface hardness.
- Cooling Rate: Rapid cooling promotes martensitic transformation, which is beneficial for hardness but increases residual stress. A balance must be struck between hardness requirements and crack resistance.
Engineering Practice Applications
Common industrial applications of wear-resistant overlay electrodes include:
- Mining equipment: excavator buckets, conveyor rollers, crusher jaws
- Cement industry: kiln seals, grinding mill liners, fan blades
- Power generation: boiler burners, ash handling equipment, coal mills
- Agriculture: plowshares, harvester components, augers
- Construction: bulldozer blades, scraper buckets, auger bits
The selection of electrode type depends on the specific wear mechanism. Abrasive wear from hard particles favors high-carbon or carbide-type electrodes, while adhesive wear and galling are better addressed by nickel-based hardfacing electrodes with good hot hardness and anti-galling properties.
Study Insights and Implications
This work underscores the importance of matching the overlay electrode composition to the specific wear conditions encountered in service. The engineering challenge lies not only in achieving high hardness but also in maintaining adequate toughness to resist cracking and spalling under impact loading. For pressure vessel and piping components that experience erosion-corrosion, nickel-based overlay electrodes with controlled carbon content provide an excellent combination of hardness, corrosion resistance, and ductility. The development of specialized electrode formulations continues to evolve, with modern compositions incorporating rare earth elements and nanostructured carbides to further enhance wear performance.