Research On Nondestructive Inspecting Method For Radial-axial Crack Of GH4169 Disk

The GH4169 alloys are widely used in parts of aircraft engine for its structure stability,excellent high temperature behavior,and good processability.However,the service behavior of the final products can be affected significantly by defects in raw materials and inappropriate processing during machining procedures,thus bringing hazards during flight.The diameter-axial crack of GH4169 disk are a serious of unique defects which includes perpendicular to the forging lines and closed type,and cannot be detected through conventional detective methods such as vertical longitudinal wave ultrasonic testing and penetration testing.On the other hand,defects hiding under the surface of the products also cannot be detected corrosion check and visual inspection,which are unusually used for surface defects detection.The ultrasonic testing and eddy current testing,as well as their application on internal crack and sub surface crack detection were introduced and discussed in this work.In order to detect the diameter-axial crack by ultrasonic testing,the contact experiment and immersion experiment were used.Through varying the angle of ultrasonic beam,detection trials were done on artificial defect and the disk with diameter-axial crack by vertical longitudinal wave,small angle longitudinal wave,shear wave and surface wave.It was found that high frequency probe back-echo monitoring are effective methods in detecting diameter-axial crack on disk.On the other hand,parameters on the depth of eddy current and capability accordingly were achieved through experimental design on series of artificial defect and the eddy current probe in the research on detection capability of eddy current testing over diameter-axial crack.A new auto-eddy current scanning system were developed during the study.The detection capability of self-developed probe and equipment,as well as optimum selecting range of main parameters were verified through the experiments designed for the disk with diameter-axial crack.It was confirmed that vertical longitudinal wave testing and penetration testing can hardly detect the defects for the characteristic of diameter-axial crack during blank test,while corrosion check was effective method in the surface diameter-axial crack detection.An optimistic strategy of GH4169 disk defects-detection considering production efficiency was proposed according to study and research experiments in this work.The strategy included adding 10 MHz small angle longitudinal bottom wave monitoring,eddy current testing during finishing stages of processing,and corrosion check at the beginning of machining.Most surface crack and internal cracks,as well as other defects can be detected at the beginning of machiningthrough improved detection scheme.Eddy current testing,penetration testing and corrosion check can be used in in-depth detection for surface and sub surface crack and other forms of defects during finishing stages of processing to ensure quality of GH4169 disk.