Design of self-sharpening plowshare based on non-uniform wear regulation and its wear resistance

Reversible plows are prone to uneven wear during cultivation, due to the complex and variable soil conditions, as well as high-intensity operational loads. High energy consumption of the tractors pulling can also shorten the service life of the reversible plows, thereby raising their operating costs. In this study, a self-sharpening plowshare was developed with high wear resistance using non-uniform wear regulation. Firstly, the wear patterns of the plowshare edge were investigated to determine the stress distribution in the three-sided wedge model. The force conditions on the plowshare edge were also obtained in the normal plane. The wear difference between the top face and bottom flank was calculated for a self-sharpening plowshare. According to the non-uniform wear characteristics of the plowshare, five sets of Co-WC/MoS₂ wear-resistant composite coatings were prepared with different chemical compositions using laser cladding technology in the laboratory. The wear behavior of these coatings was tested using a multifunctional friction and wear testing machine. The wear rate ratio between the coating and substrate was then calculated for each sample group. Finally, three representative coating protocols were selected to fabricate the plowshares, along with a control group of untreated conventional ones. The field tests were carried out under extreme sandy soil conditions across 60 hm² of cultivated land. The wear resistance and self-sharpening properties of the self-sharpening plowshares were evaluated to measure the plowshare width, edge thickness, and mass. Research indicates that the conventional plowshares were prone to rapid blade dulling and failure due to the differential stress distribution across their top face and bottom flank. The maximum wear difference between the conventional plowshare (Sample 1) and the self-sharpening sample (Sample 3) reached 14.02 mm after the wear and field tests. There was a great variation in the width during tests. The width loss rate at the front end of Sample 2 (0.08 mm/hm²) was 2.96 times that of Sample 3. While there were similar wear characteristics in the middle and rear sections. In plowshare edge thickness, Sample 1 exhibited the typical edge blunting after wear, with a 66.62% increase in the edge thickness after tilling 60 hm². In contrast, the self-sharpening plowshares (Samples 2 and 3) shared the edge thickness reductions of 26.90% and 17.00%, respectively, over the same 60 hm² tilling cycle. Although Sample 4 exhibited a low coating wear rate, its plowshare edge thickness closely matched the wear trajectory of uncoated Sample 1. In mass change, the self-sharpening plowshares demonstrated significant advantages during the 60 hm² tillage cycle. Sample 3 (with a coating-to-substrate wear ratio of approximately 1:3.67) exhibited a mass loss rate of 7.98 g/hm², while Sample 2 (with a coating-to-substrate wear ratio of approximately 1:2.38) shared a mass loss rate of 8.10 g/hm². The superior performance was achieved compared with Samples 1 and 4. A comparison indicated that the blunt edge growth rate was controlled below 0.03 mm/hm², when the wear rate ratio between coating and substrate was closest to 1:3.67 (as in Sample 3), indicating the optimal self-sharpening performance and the longest service life. Once the coating's wear rate was excessively high, the coating material failed to maximize the protection of the plowshare substrate. When the coating wear rate was too low, the prolonged wear caused greater top-layer abrasion than the bottom layer, thus thinning the plowshare edge for the fracture risk. The wear-resistant layer failed to fully exhibit its properties, similarly reducing the plowshare's performance. These research findings can provide the theoretical support and technical references to develop the high-performance plows. It is also of significant importance to advance the sustainable development of agricultural machinery.