Bionic Design of Agricultural Plowshare Overlay Microstructure and Wear Resistance

Literature Overview

This study applies biomimetic design principles to optimize the microstructure of overlay layers deposited on agricultural plowshares, which are subjected to severe abrasive wear from soil, rocks, and crop residue. By drawing inspiration from natural materials such as shark skin, fish scales, and bone tissue, the research develops novel overlay microstructures that achieve superior wear resistance while maintaining adequate toughness to prevent catastrophic failure.

Core Technical Content

Bio-Inspired Design Concepts

Biological Model	Structural Feature	Engineering Application	Performance Benefit
Shark skin	Denticles with micro-grooves	Surface micro-texture on overlay	Reduced friction, self-cleaning
Fish scales	Overlapping layered structure	Multi-layer overlay with graded hardness	Progressive wear resistance
Bone tissue	Lamellar structure with mineral reinforcement	Lamellar overlay with hard particle reinforcement	Crack deflection, damage tolerance
Spider silk	Hierarchical fiber structure	Fiber-reinforced overlay matrix	High toughness with adequate hardness
Nacre (mother of pearl)	Brick-and-mortar structure	Hard particle in soft matrix composite	Superior fracture toughness

Multi-Layer Graded Overlay Design

The biomimetic overlay design employs a three-layer graded structure:

Layer	Composition	Hardness (HV)	Function
Surface layer	High-carbon martensite + TiC/ WC particles	800–1000 HV	Primary abrasion resistance
Transition layer	Medium-carbon austenite-martensite	400–600 HV	Toughness buffer, stress distribution
Bond layer	Low-carbon austenite	200–350 HV	Strong bond to substrate, low residual stress

Microstructural Optimization Parameters

The bionic design achieves optimal performance through the following microstructural features:

Lamellar spacing control: The spacing between hard lamellae is optimized to 5–20 μm, which corresponds to the critical crack propagation distance for the specific wear conditions encountered in agricultural soil.
Particle distribution: Hard particles (TiC, WC, Cr₃C₂) are distributed in a gradient pattern — higher concentration at the surface, decreasing toward the substrate — mimicking the nacre brick-and-mortar structure.
Grain orientation: Columnar grains are oriented perpendicular to the surface, providing crack deflection similar to the hierarchical structure in bone tissue.
Retained austenite: 20–35% retained austenite in the transition layer provides work-hardening capacity during service, analogous to the viscoelastic behavior of biological tissues.

Wear Performance Comparison

Overlay Type	Hardness (HV)	Abrasion Resistance	Impact Toughness (J/cm²)	Service Life Improvement
Conventional hardfacing (Fe-Cr-C)	700–800	Baseline	3–5	1×
Bionic multi-layer overlay	800–1000	2.5–3.5×	8–12	3–5×
Single-layer WC overlay	850–950	3.0–4.0×	2–4	2–3×
Bionic + surface texture	800–1000	3.5–5.0×	8–12	4–6×

Process Implementation

The bionic overlay is deposited using a combination of processes:

Bond layer: Submerged arc welding (SAW) with low-carbon austenitic wire (e.g., ENiCrMo-15 equivalent), heat input 3–5 kJ/mm.
Transition layer: Flux-cored arc welding (FCAW) with medium-carbon austenitic wire containing TiC particles, heat input 2.5–4.0 kJ/mm.
Surface layer: Plasma transferred arc (PTA) or laser cladding with high-carbon martensitic alloy containing WC or TiC particles, heat input 1.5–3.0 kJ/mm.

Post-weld heat treatment at 550–600°C for 1–2 hours stabilizes the microstructure and reduces residual stresses without significantly reducing surface hardness.

Key Reflections and Insights

The biomimetic approach to overlay design represents a paradigm shift from the conventional "harder is better" philosophy. The study demonstrates that the optimal wear-resistant structure is not the hardest structure, but rather a structure that manages the interplay between hardness, toughness, and damage tolerance in a way that mimics the evolutionary optimization found in natural materials.

The practical significance is substantial: agricultural machinery manufacturers can achieve 3–5 times the service life of plowshares with bionic overlay designs, translating directly into reduced replacement frequency, lower maintenance costs, and reduced fuel consumption due to reduced plowing resistance. The surface micro-texture inspired by shark skin reduces soil adhesion, which not only improves wear life but also reduces the energy required for plowing operations.

From a standards perspective, the overlay must meet the requirements of GB/T 12469 for wear-resistant weld deposits, and the bond strength must comply with relevant agricultural machinery standards (GB/T 23139 or ISO 17034). Non-destructive testing should include magnetic particle inspection for surface cracks and ultrasonic testing for bond quality, following JB/T 4730 or equivalent.