China is one of the few major agricultural countries in the world. With the accelerating pace of economic development, my country has begun to promote agricultural mechanization and automation on a large scale. According to statistics, the degree of agricultural mechanization in my country has reached 48% in 2000. However, due to the low manufacturing process and level of agricultural mechanization in my country, there is still a large gap between product reliability, safety, durability and adaptability and those of developed countries. In particular, the key parts of agricultural machinery directly affect its service life. The failure of key wear-resistant parts such as rotary tillage blades, fixed blades, ear picking plates, rotary blades, crushing blades, cutting blades, plows, shovels, harvester blades, furrow openers, etc. greatly increases the maintenance cost and seriously affects the working efficiency of agricultural machinery. Most of the current agricultural machinery maintenance is just a simple disassembly and replacement of parts, which not only increases the operating costs of agricultural machinery enterprises, but also hinders the promotion and popularization of agricultural mechanization in my country.

For the relatively slow-developing traditional agriculture, advanced laser technology is applied to the agricultural field, and the most eye-catching one is the laser cladding technology used for the repair and strengthening of agricultural machinery.

Laser cladding is a surface modification technology for substrates. By presetting the cladding path, laser irradiation is used to quickly melt the cladding material and the substrate surface into a molten pool where the laser passes, and then quickly solidifies into a cladding layer with metallurgical bonding and low dilution, so that mechanical parts can be repaired in situ, or the wear resistance, corrosion resistance, heat resistance, and oxidation resistance of the original substrate surface can be improved.

Compared with traditional processing technology, laser cladding technology has the following characteristics:

• The cladding layer can form a metallurgical bond with the substrate;
• The substrate is less affected by heat and is not easy to deform;
• The dilution rate of the cladding layer is low, saving expensive cladding materials;
• The thickness of the cladding layer can be controlled;
• Specific parts of parts and parts that are difficult to handle by other methods can be repaired.

Before cladding and repairing the parts of agricultural machinery, the surface of agricultural machinery parts needs to be pretreated. Due to the harsh working environment of agricultural machinery, the surface of agricultural machinery parts often carries dirt, oil, water, fertilizer, pesticide, rust, oxide layer, etc. Therefore, compared with parts in other fields, the repair of parts is more complicated. For agricultural machinery parts, the general operation is to use water to wash away the surface dirt of the soil-touching tillage parts. If the dirt on the damaged surface is relatively firm, it can be cleaned by mechanical sandblasting, and the engine, shaft and other parts are first cleaned with detergent to remove the oil. After that, the surface to be clad is polished with sandpaper and cleaned with acetone to avoid surface stains entering the cladding layer during laser cladding, causing defects and affecting the quality and performance of the cladding layer.

The main technologies for traditional agricultural machinery repair are heat treatment, chromizing treatment, arc spraying, etc., but they are all difficult to meet the requirements of wear resistance, corrosion resistance, and pollution-free required by agricultural machinery. With the continuous development of laser cladding technology, the performance of the prepared cladding coating is becoming more and more excellent; therefore, scholars have begun to study the application of laser cladding technology in the repair and strengthening of agricultural machinery. In addition to repairing damaged rotary blades, fixed blades, ear picking plates, rotating blades, crushing blades, cutting blades, plows, and shovels, laser cladding technology can also be used to enhance the performance of existing agricultural machinery parts.

As early as 2009, Chinese researchers explored the laser treatment of the surface of rotary blades. By designing orthogonal experiments and performing extreme difference analysis, it was found that the main factors affecting the surface strengthening effect of the substrate were laser power> scanning speed> spot diameter. After the material was clad by laser surface, the matrix structure was significantly refined, and many relatively fine high-carbon martensite was formed in the cladding area, which increased the microhardness, thereby improving the wear resistance of the rotary blade. After that, the design optimization experiment was used to compare the effects of common heat treatment, laser heat treatment and laser cladding single surface modification technology on the extension of the service life of the lawn mower blade, and it was found that laser cladding was better than the former two.

Therefore, exploring advanced repair technologies and performance improvement methods for key agricultural machinery components such as rotary tillers, fixed blades, ear picking plates, rotating blades, crushing blades, cutting blades, plowshares and shovels is of great practical significance for improving the service performance of agricultural machinery and extending its service life.