When testing the silver impregnated graphite pad of the waterlubricated thrust bearing for a nuclear main pump,unusual vibration and noise occur at transient thermal like working conditions,and serious wear are observed on the surfaces of both graphite pad and thrust plate after the thrust bearing disassembling,and even some partial peeling occur on local region on graphite pad surface.The wear debris was analyzed by using a number of techniques including chemical,optical,XRD,SEMEDS,TEM,and EPMA to study their phase structure,morphology,composition and microstructure as well as worn surface features,respectively.The wear behavior and process of the graphite pad and Stellite hardfaced thrust plate in thermal transient were identified,and the conclusion was drawn that the waterlubricated thrust bearing is in a condition of boundary lubrication state,and local dry friction was taken place.It is suggested that,using carbon fiber composite instead of silver impregnated graphite to improve the wear performance of thrust bearing,optimizing the surface configuration of pad to reduce thermal deformation during friction,and increasing surface hardening layer on the supporting contact faces to control the fretting wear due to the high stress contact among the bearing components.