Zhuojin Pipe Fitting Co., LtdFriction and Wear Properties of Q235 Structural Steel Arc Surfacing Overlay
Literature Overview
Published in Materials Protection (Vol. 52, No. 10, 2019, pp. 70-74), this paper by Li Cong, Chen Xueqin, Peng Daoheng, and Wang Jinfeng from Hubei University of Automotive Technology and Jiangsu University examines the friction and wear behavior of CO2 gas-shielded flux-cored wire arc surfacing deposits on Q235 structural steel. Supported by the Central Guidance of Local Science and Technology Development Special Project (2019ZYYD023) and Hubei Provincial Department of Education Key Science Project (D20181801), the study provides valuable insights into the tribological performance of economic surfacing solutions for general structural applications.
Core Technical Content and Methodology
The research employed CO2 gas-shielded flux-cored wire arc surfacing to create a strong overlay on Q235 steel substrate. Characterization included optical microscopy, scanning electron microscopy (SEM), and friction-wear testing on three distinct zones: substrate region, overlay layer, and interface region.
Microstructural Evolution Across Zones
The interface region exhibited notably fine needle-like martensite with significantly refined grain structure compared to both substrate and overlay. This grain refinement at the interface is attributed to the rapid cooling experienced during the welding thermal cycle at the boundary zone.
| Zone | Microstructure | Friction Coefficient | Wear Morphology |
|---|---|---|---|
| Substrate | Ferrite-pearlite (Q235) | Highest | Large wear area, severe plastic deformation, delamination pits |
| Overlay Layer | Martensitic structure | Moderate | Moderate wear with plastic deformation |
| Interface Region | Fine needle martensite, refined grains | Lowest | Reduced plowing, improved resistance to plastic deformation |
Wear Mechanism Analysis
Secondary electron imaging of wear surfaces revealed distinct wear mechanisms in each zone. The substrate showed large wear areas with severe plastic deformation and localized delamination pits, characteristic of adhesive wear combined with material removal. The overlay layer exhibited moderate wear characteristics with some plastic deformation. The interface region showed the most improved wear behavior, with reduced plowing marks and diminished plastic deformation compared to the overlay layer.
Interface Enhancement Mechanism
The superior wear resistance of the interface region is attributed to intense elemental diffusion and metallurgical reactions occurring during the welding process. These reactions produce a high volume of hard phases that enhance the microstructural wear resistance. The diffusion of alloying elements from the flux-cored wire into the substrate creates a gradient composition zone with enhanced mechanical properties.
Engineering Practice Implications
For structural steel applications where surface wear resistance is required without replacing the entire component:
- CO2 flux-cored wire surfacing provides an economical solution for improving wear resistance of Q235 components such as structural brackets, supports, and connection plates.
- The interface region's superior wear performance suggests that the transition zone between overlay and base metal is often the most critical area for service durability.
- The low friction coefficient at the interface indicates potential for reduced energy loss in sliding applications.
Key Technical Insights and Reflections
The discovery that the interface region outperforms both the substrate and overlay in wear resistance is counterintuitive and highly significant. In conventional thinking, the overlay layer is expected to provide the best wear performance. However, the metallurgical reactions at the interface create a unique microstructure with fine martensite and abundant hard phases that exceed the performance of the overlay itself.
This finding has important implications for surfacing design. The thickness of the overlay may not be the sole determinant of performance; the quality of the interface bonding and the extent of interfacial reactions are equally critical. Engineers should pay attention to:
- Maintaining clean base metal surfaces to promote good metallurgical bonding
- Controlling heat input to optimize interfacial reactions without excessive base metal dilution
- Considering the interface region as a functional component rather than merely a transition zone
The wear morphology observations, particularly the delamination pits on the substrate, highlight the importance of proper surface preparation and the limitations of uncoated structural steel in wear applications.
Study Value and Outlook
This research demonstrates that even relatively simple surfacing processes can produce significant improvements in wear performance, particularly at the interface region. The economic viability of CO2 flux-cored wire surfacing for Q235 structural applications makes this technology accessible for widespread industrial use. Future work should investigate the long-term stability of the interface microstructure under cyclic loading, examine the effect of surfacing parameters on interface quality, and explore multi-layer approaches to further enhance performance. The findings are particularly relevant for automotive, construction, and general manufacturing industries where cost-effective wear protection is needed.