The wear characteristics of thrust washer in conflux planetary gear train of power shift transmission

The wear between planet gear and thrust washer has been investigated based on the thrust washers in planetary transmission. The reasons leading to the wear failure are studied and the measurements for the reduction of abrasive wear are also exploited. A typical wear failure of thrust washer has been analyzed in terms of macromorphology observation, SEM observation of microstructure, material composition test, the metallographic analysis on radial cross section, and microhardness testing. Oil viscosity, oil contamination, and element spectra are analyzed and used to interpret the failure reasons. Through comprehensive analyses of metallographic structure and microhardness, the temperature distribution of thrust washer is obtained, which demonstrate that the adhesive wear is the main wear type for thrust washer although the fatigue wear is also observed. The most wear of thrust washer can be attributed to the great axial force during the working process, which leads to big contact stress. The high temperature at friction surfaces could surpass critical temperature and cause phase transition of austenite in the material. Inadequate cooling effect due to lack of lubrication oil is the main reason for high temperature caused by wear. Upon the comprehensive analyses, in the last section of this work some measurements are put forward for the reduction of the wear.

► The adhesive wear is main wear type of thrust washer failure.
► The axial force is the main reason for the damage of thrust washer.
► The local temperature on the friction pairs can reach up to 800 °C.
► Inadequate lubrication is one of main reasons for high temperature by wear.
► Serious contamination of oil can reduce the service life of friction pairs.