On the initiation and propagation of fatigue cracks in WC-Co

[摘要] This research examines fatigue in WC-Co, both under compressive and tensile loading conditions.A new macro-mechanism for compression fatigue crack propagation is put forward, whichcontradicts existing data on compression fatigue cracks as being self-limiting. Evidence of thismacro-mechanism is presented in the form of final crack length versus number of cycles data, andmicrographs of the compression fatigue cracks. A finite element study of the stress distributionin the WC-Co microstructure during compression fatigue loading has been developed. This modelverifies possible methods of compression fatigue crack initiation. Examination of tensile fatigueand fast: fracture surfaces is used to show that fatigue is a separate mechanism to fast fracture inWC-Co. Characteristic features of the fatigue fracture surface are presented. A possible fatiguecrack propagation mechanism is also presented. Finally, fatigue crack growth rate data in the formof the Paris equation is presented for WC-Co grades T6 and G6.

[发布机构] University of the Witwatersrand