Zhuojin Pipe Fitting Co., LtdBiomimetic Design of Weld Overlay Microstructure for Agricultural Plough Shares
Literature Overview
This study by Li Muqin, Cai Dingsen, Zhuang Minghui, and colleagues from the Engineering Research Center for Metal Wear-Resistant Materials and Surface Technology at Jiamusi University, published in the Welding Journal (Hanjie) in 2017, Issue 5, pages 1–6, presents a biomimetic approach to designing wear-resistant overlay welds for agricultural plough shares. The research was supported by the National Science and Technology Support Plan Project (2011BAD20B03), Jiamusi University Graduate Innovation Project (LM2014_003), and the Jiamusi University President Innovation Fund (xzyf2014-07). The core idea is to replicate the surface microstructure morphology of dung beetle exoskeletons through controlled alloy design and welding process optimization.
Biomimetic Design Concept and Alloy Development
The dung beetle exoskeleton exhibits a hierarchical microstructure that provides exceptional wear resistance through a combination of hard phases dispersed in a tough matrix. The research team designed Fe-Cr-C-(B₄C)ₓ series metal-cored wires, where the B₄C addition level was systematically varied to tune the overlay microstructure toward the beetle-inspired morphology. The B₄C serves a dual purpose: it acts as a source of hard boride carbide phases and influences the solidification path of the alloy through its effect on the carbon and boron activity in the weld pool.
| Parameter | Description |
|---|---|
| Wire composition | Fe-Cr-C-(B₄C)ₓ metal-cored wire |
| Welding process | CO₂ gas shielded arc welding |
| Welding technique | Reciprocating oscillating cladding |
| Matrix phases | Martensite, lower bainite |
| Network phase | (Cr,Fe)₃(B,C) |
| Dispersed particles | TiC hard points (minor) |
| Wear resistance | 3–4 times that of 65Mn steel |
Microstructural Analysis and Wear Performance
The overlay microstructure consists of a martensitic and lower bainitic matrix with a network of (Cr,Fe)₃(B,C) phases along grain boundaries, supplemented by a small amount of TiC hard particles. EBSD phase analysis confirmed the phase distribution and orientation relationships. The martensitic matrix provides high hardness, while the (Cr,Fe)₃(B,C) network phase forms a continuous reinforcement framework that resists abrasive penetration. The TiC particles, derived from the Ti content in the base steel or wire flux, act as additional hard points that enhance resistance to adhesive wear.
The wear resistance improvement of 3–4 times compared to 65Mn steel is attributed to the synergistic effect of the three-phase microstructure. The martensite provides a hard substrate, the network boride carbide phase creates a barrier against abrasive particle intrusion, and the TiC particles serve as wear-resistant anchors. This biomimetic design philosophy is noteworthy because it does not merely seek to maximize hardness but rather to engineer a balanced microstructure that mimics the proven durability of biological materials.
Engineering Practice and Process Considerations
The use of CO₂ gas shielded welding with reciprocating oscillation is a practical choice for field application on agricultural machinery. CO₂ shielding is economical and widely available, making this technology accessible for repair shops and maintenance operations. The oscillating welding technique ensures uniform deposition and helps control the dilution ratio, which is critical for maintaining the designed alloy composition in the overlay. However, the reciprocating motion must be carefully controlled to avoid excessive heat input that could soften the martensitic matrix or cause excessive grain growth.
A potential concern in practical application is the brittleness associated with the (Cr,Fe)₃(B,C) network phase. While this phase enhances wear resistance, an excessive network could compromise the impact toughness of the overlay, making it susceptible to chipping under high-impact loading conditions typical in ploughing operations. Engineers should consider the service loading spectrum and potentially adjust the B₄C addition level to balance wear resistance against impact resistance.
Summary
This paper demonstrates a creative and effective approach to wear-resistant cladding design by drawing inspiration from biological structures. The Fe-Cr-C-(B₄C)ₓ system, processed through CO₂-shielded oscillating welding, achieves a biomimetic microstructure with martensite, lower bainite, and (Cr,Fe)₃(B,C) network phases that deliver 3–4 times the wear resistance of conventional 65Mn steel. The practical accessibility of the welding process and wire consumables makes this technology highly suitable for agricultural machinery repair and maintenance applications.