| Superalloy GH4169 and titanium alloy TC17 have excellent physical and mechanical properties,which are widely used in aerospace field and are the key materials for manufacturing typical load-bearing parts of aero-engine.At the same time,as a typical difficult to machine material,the machined surface quality and service life of its parts have always been a research hotspot.Based on the anti-fatigue manufacturing of GH4169 and TC17 specimens,through the surface integrity test and fatigue life test,this paper studies the influence of processing parameters on the surface integrity and the surface integrity on the fatigue performance of the specimens in ball milling finishing,which provides a new research idea and valuable reference for improving the fatigue performance of superalloy and titanium alloy parts.Firstly,the surface integrity of GH4169 and TC17 ball milling was studied.The influence of ball milling parameters on the surface integrity was studied through ball milling experiments.The influence mechanism and law of cutting parameters on surface integrity indexes are analyzed.It is found that the feed rate per tooth is the dominant factor affecting the machined surface roughness of GH4169 and TC17,and the cutting depth has the most significant effect on the work hardening and residual stress.The results show that the residual tensile stress is obtained on the surface of GH4169,while the residual compressive stress is obtained on the surface of TC17.The plastic deformation of the surface material is obvious.The different degree of plastic deformation under different cutting parameters is the main reason for the change of machining hardness and residual stress.Secondly,the fatigue properties of GH4169 and TC17 ball milling specimens were studied.Finish machining and fatigue life test were carried out on the fatigue specimens.Combined with fatigue life data and fatigue fracture analysis,the influence of machined surface integrity on fatigue life was explained.The fatigue sources of GH4169 are all located in the sub surface,and the fatigue life is mainly affected by the surface hardness.With the increase of the surface hardness,the fatigue life is significantly improved.When the surface roughness of TC17 specimen is less than R_a0.35?m,the fatigue life is mainly affected by the surface hardness,and increases significantly with the increase of surface hardness.When the surface roughness is more than R_a0.35?m,the surface roughness begins to become the dominant factor affecting the fatigue life,and the larger the roughness is,the worse the fatigue performance is.By optimizing the milling parameters,the fatigue life of Superalloy GH4169 and titanium alloy TC17 increased from 1.83×10~5and 6.23×10~5 to 3.01×10~5 and 12.24×10~5,respectively.Finally,in order to improve the fatigue life of the specimens,the optimal processing parameters of Superalloy GH4169 and titanium alloy TC17 in ball end milling are v_c=20m/min,a_p=0.5mm,f_z=0.04 mm/z,a_e=0.2mm and v_c=40m/min,a_p=0.4 mm,f_z=0.08mm/z,a_e=0.2mm,which provide guidance for ball end milling of Superalloy GH4169 and titanium alloy TC17. |
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