Wear on steel tillage tools: A review of material, soil and dynamic conditions

The tribological process between the tillage tools and the soil is quite complex. Wear on tillage tools changes depending on the material of the tool, opposing material (soil), environment (moisture, temperature), and dynamic factors (stress on sliding surface, sliding time, sliding speed, and sliding type). Chemical composition, microstructure, and mechanical properties of the material from which the tools are made; soil properties such as texture, structure, density, moisture, rock and gravel content; operating conditions such as tillage speed and depth; geometry and surface roughness of the tool, and impact angle with the soil are effective on wear. It is generally accepted that tillage tools go through low-tensioned and two-body abrasive wear. The ratio between the hardness of the tools (Hs) and the hardness of the abrasive soil particles (Ha) determines wear mechanisms. When this ratio is lower than 0.8, microcutting and microplowing mechanisms are dominant. Meanwhile, when the hardness value of the tool's surface is close to or higher than the hardness value of the soil particles, microcracks, fragmentation, and peel-off of the hard phases occur. Therefore, hardness alone may not be sufficient to ensure tribological performance, and hardness and toughness should be balanced since tillage tools are exposed to movements such as impacts.