PTFE pipe leaked oil after many times used. Based on macro and microscopic observation of facture sur鄄
face by OM and SEM, the fracture failure of pipe was investigated. Accoding to the analysis results of the pipe , the main
reason of leak failure was that the pipe inner surface had manufactural defect. During many times used procesee, under the
high oil pressure, the manufactural defect expanded through fatigue cracking until some area leak oil.