WANG Zhiwen, LIU Xiubo, ZHOU An, ZHANG Feizhi, ZHANG Shihong
Owing to the enormous amount of work performed and harsh working conditions of agricultural and forestry machinery, many critical moving parts are subjected to long-term overloads, which results in reduced service life and hinders the further development of agricultural and forestry machinery. Therefore, reducing the wear and tear of key moving parts is of great practical importance in agroforestry production. Surface modification technology has become an important method for improving the wear resistance of key moving parts of agricultural and forestry machinery. The surface modification technology is adaptable, easy to operate, and inexpensive. Surface technologies, such as thermal spraying, built-up welding, spray welding, and laser cladding, can improve the wear resistance of key moving parts of agricultural and forestry machinery. This increases the efficiency and reduces the intensity of agricultural and forestry machinery work. Thermal spraying technology has unique characteristics such as lightweight equipment, process flexibility, easy operation, short machinery-repair time, higher adaptability, controllable coating thickness, and suitability for a wide range of base materials. Built-up welding technology offers several advantages, including high bonding strength between the fused cladding and the substrate, good impact resistance, cladding composition, and coating thickness, which can be adjusted from 2 to 30 mm. Moreover, it imparts properties that can be easily adapted to suit a variety of situations. Spray-welding technology involves preheating the alloy powder coating on the surface and subsequently heating it to 1 000–1 300 ℃. The borides and silicides produced in the coating formed good bonds with the substrate surface and between the particles. The final formation was a compact and crystalline metallic structure that formed a metallurgical bond with a substrate of approximately 0.05 to 0.1 mm. The fused coating exhibited excellent impact, abrasion, and corrosion resistance. Laser cladding is a recent technology used for manufacturing functional coatings on metal surfaces, and has high cladding efficiency, good flatness of the coating, and low overall cost. The advantages of laser cladding include the metallurgical bond between the substrate and coating, high melting efficiency, rapid cooling, high powder utilization rate, flat molten cladding, a wider selection of materials for cladding, and selective localized repair. This study outlines the working conditions and wear mechanisms of agricultural and forestry machinery. The application of four surface modification techniques—thermal spraying, spray welding, cladding, and laser cladding—to key moving parts of agricultural and forestry machinery and the advantages and disadvantages of each surface modification method are summarized. Based on this, the status of research on ground technology for agricultural and forestry machinery is presented. Finally, key scientific issues and challenges in the current research are summarized, and future research directions are discussed.