Improving the fracture toughness of agricultural soil-engaging components can mitigate the detrimental effects of hard particles in the soil while maintaining the wear resistance of the components, thereby improving the service performance. The wear resistance of the parts can be improved by surface treatment, but the surface toughness after treatment still needs to be further improved. In this study, WC10Co4Cr@YSZ (Yttria Stabilized Zirconia) core-shell structured composite powder was synthesized by modifying commercial WC10Co4Cr powder using the sol-gel method, and WC10Co4Cr coatings were prepared using the powders before and after modification. The microstructure of the powder and coatings were characterized. The mechanical properties and wear resistance of the coatings were evaluated through microhardness, nanoindentation, and friction testing. The hardness of the YSZ-modified composite coating was comparable to that of the unmodified coating, yet it exhibited lower porosity and twice the fracture toughness. Wear test results indicated that the coating's wear loss was greatly reduced compared with the substrate. In addition, the wear rate of the YSZ-modified coating was 71.11 % lower than the unmodified coating, demonstrating its exceptional wear resistance. The findings show that incorporation of YSZ into the coating system further enhanced wear resistance. The strengthening mechanisms resulting from the YSZ inclusion include the pinning effect, which controls the size and distribution of the WC grains, the shell structure that prevents overheating, and the improved fracture toughness of the coating. This work provides a new way to extend the service time of agricultural soil-engaging components.

To elucidate the wear mechanisms of the scraper in shield tunneling through sandy pebble strata, this study aims to achieve high efficiency and low wear during the tunneling process. We evaluate the operational parameters and tool wear characteristics of a 9-m diameter spoke-type shield machine used on the Beijing Daxing Airport Line. The analysis focuses on the wear values of the scrapers and rippers, wear of the scraper in different wear forms, and scraper wear relative to the position of the rippers obtained from the field. The study yielded the following conclusions. The wear values of scrapers on different spokes vary significantly owing to ripper protection. The wear of the scrapers can be categorized into six types: tooth chipping, local damage of teeth, wear of side teeth, wave-type of wear, wear on intermediate teeth, and flat wear, with the majority exhibiting wear on the side and intermediate teeth. The 0 degrees spoke maintained the initial shape of the scrapers, making it more suitable for tunneling in sandy pebble strata. Based on the differences in the relative positions of the ripper and scraper, a model is proposed to determine the ripper plowing influence area. It was found that this area depends on the geological conditions of the soil; thus, the influence angle of ripper plowing in the considered sandy pebble strata is determined to be between 35 degrees and 50 degrees. The results obtained in this study provide a theoretical reference for optimizing scraper layouts in shield construction, even when operating under varying geological 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.