CLADDING TECHNOLOGY SHANXI CO., LTDDevelopment of High Cracking-Resistant Wear-Resistant Overlay Welding Electrodes
Literature Overview
This 2009 publication by Tang Wenbo, Guo Yungang (Zhengzhou University) and Wei Jianjun, Huang Zhiquan (Zhengzhou Mechanical Research Institute) focuses on the design and development of overlay welding electrodes that simultaneously achieve high wear resistance and excellent resistance to cracking. This dual-objective approach addresses one of the most persistent challenges in overlay welding: the inherent trade-off between hardness (which improves wear resistance) and ductility (which improves crack resistance).
Core Technical Content
The fundamental challenge addressed is that high-carbon, high-alloy compositions required for wear resistance typically produce hard, brittle microstructures that are prone to hot cracking during solidification and cold cracking during cooling. The study proposes a composition and microstructure design strategy that decouples these competing requirements through careful alloy design.
Electrode Composition Design
The developed electrode compositions are based on martensitic stainless steel systems with controlled carbon and alloy content. The key design principles include:
| Design Parameter | Target Range | Rationale |
|---|---|---|
| Carbon content | 0.3 to 0.6 wt% | Balances hardness and ductility |
| Chromium content | 10 to 16 wt% | Provides corrosion resistance and hardenability |
| Molybdenum content | 1.0 to 3.0 wt% | Improves hardenability and reduces cracking |
| Nickel content | 2.0 to 5.0 wt% | Stabilizes austenite, reduces cracking |
| Manganese content | 0.8 to 1.5 wt% | Controls grain size, reduces hot cracking |
| Silicon content | 0.3 to 0.8 wt% | Deoxidizer, controls slag properties |
The addition of nickel (2 to 5 wt%) is particularly significant as it promotes retained austenite formation, which accommodates thermal stresses during cooling and significantly reduces cold cracking susceptibility. Molybdenum (1 to 3 wt%) improves the hardenability of the martensite, allowing adequate hardness to be achieved at lower carbon levels, thereby reducing the embrittling effect of high carbon.
Microstructure and Performance
The deposited weld metal exhibits a mixed microstructure of tempered martensite, retained austenite (8 to 15 vol%), and fine carbides. This microstructure achieves a hardness of 45 to 55 HRC while maintaining sufficient toughness (Charpy impact energy above 20 J at room temperature). The retained austenite acts as a crack-arresting phase, deflecting cracks and reducing the driving force for crack propagation.
The study demonstrates that the cracking resistance is improved through three mechanisms: (1) the retained austenite provides transformation toughening; (2) the lower carbon content reduces the hardenability and residual stress; and (3) the molybdenum addition promotes finer grain structure, which reduces the grain boundary area susceptible to intergranular cracking.
Engineering Practice Integration
In industrial applications, these electrodes have been used for repair and hardfacing of components in the mining, cement, and power generation industries. Typical applications include repair of worn crusher components, hardfacing of pump impellers, and overlay of bearing surfaces. The electrodes can be used with standard SMAW (shielded metal arc welding) equipment, making them accessible to field repair operations without specialized equipment.
The recommended welding procedure includes: preheating to 100 to 150 °C for thick sections, using short arc length (1 to 2 times wire diameter), maintaining consistent travel speed, and limiting interpass temperature to below 250 °C. Post-weld heat treatment at 550 to 600 °C for 2 hours can further reduce residual stresses and improve toughness.
Study Insights
The key insight from this work is that the trade-off between wear resistance and crack resistance can be partially overcome through microstructural design rather than composition compromise. By introducing retained austenite through nickel addition and controlling the tempering state of the martensite, both properties can be improved simultaneously. This approach aligns with the broader principle in materials design that microstructural control often provides more flexibility than composition optimization alone. In practice, I have found that electrodes designed with this philosophy perform particularly well in applications where the component is subjected to both abrasive wear and impact loading, such as excavator buckets and crusher hammers.