Friction and Wear Mechanism of Silver-Coated Layer of Aviation Hydraulic Plunger Pump’s Slipper

Hydraulic piston pump is widely used in aviation machinery because of its compact structure, stable transmission, high power ratio, high pressure and high flow rate. With the rapid development of aviation technology and the high-strength use of aviation equipment, it is very important whether the plunger pump can withstand high pressure, high speed and high performance after service. As one of the key friction parts of the hydraulic plunger pump, the slipper boots move under extreme conditions of high pressure, high speed, high load and large displacement for a long time, and the force is very complicated. The end face of the slipper shoe is more prone to impact contact friction and wear, and the coating is more prone to peeling, which ultimately leads to the shortening of the service life of the hydraulic piston pump. Therefore, it is very important to study the wear behavior of the end face of the hydraulic plunger pump. The plunger in a hydraulic piston pump operates under extreme conditions, enduring high pressure, high speeds, and heavy loads over extended periods. The resultant friction and wear at the interface lead to surface damage on the slipper shoe. The damage includes spalling of the silver coating and corrosion of the mesh, which significantly impacts the equipment's safety and service life. To investigate this issue, we conducted post-service analysis of the slipper's end face using an ultra-depth microscope, a Vickers hardness tester, SEM, and EDS. This analysis aimed to elucidate the mechanisms behind the mesh formation on the tin bronze surface of the slipper and the spalling of the silver coating. The results showed that the defects such as pores and segregation on the surface of slipper shoes tin cast bronze would cause the bonding strength of the silver plating layer to decrease, and serious friction and wear would lead to spalling of the silver plating layer under actual working conditions. The spalling silver particles would further aggravate the wear of the silver plating layer during the wear process. The mechanism of black mesh on the surface of sliders was analyzed, and it was found that the reverse segregation pattern of matrix cast tin bronze was corroded by acid solution to form Cu-Sn-O compound during the process of silver deplating, resulting in black mesh similar to metallographic grain boundary pattern on the interface.