Research On Surface Integrity Based On End Milling Process Of GH4169

Nickel-based alloys have been extensively used as critical components in theaerospace industry, especially in the hot sections of gas turbine engines. Statisticalresults from available literatures show that fatigue failure is the most common failuremode; meanwhile, the analysis result give a conclusion that this failure process isheavily dependent on the mechanical, physical and chemical state of the surfaceregion which is named as surface integrity. Surface integrity, which can be describedas indicators and standards of the technical state of the product surface layer, mainlyincludes the geometric morphology, the mechanical properties of residual stress andmicro-hardness and metallographic state.In this paper, the generation mechanism of surface defect is studied based on themilling experiment of GH4169and the analysis with Scanning Electron Microscope(SEM) and Energy Dispersive X-ray (EDX). Surface geometry defects aftermachining process of the nickel-based alloys are classified as follow: chatter marksperpendicular to the direction of relative work-tool motion, long tear and grooveparallel to the direction of relative motion between workpiece and tool, built-up-edge(BUE) and cavity. The EDX result indicates that the generation of tear, cavity andBUE are related to the carbide particles. These carbide particles are hard particleprecipitations in the grains or at the grain boundary formed in the preparation processof the nickel-based alloy. When the particles are peeled from the surface, cavitiesform in the cutting process. And tear forms as a consequence of the detached carbideparticle being dragged along the machining direction. In the second part of this paper,the variation law of the surface defects changing with the cutting conditions isdiscussed. The results show that the cutting speed has a positive effect on the numberof BUE. Inversely, the damage areas of large tears decrease significantly with theincrease of cutting speed. Meanwhile, the generation of surface defects can beeffectively inhibited due to the application of cutting fluids, as the frequencies orimpact areas of tear, cavity and BUE decrease dramatically. However, the effect offeed rate on the degree of surface damage is marginally considered as compared tocutting speed and the coolant conditions.In conclusion, the generation mechanism of surface defects and the impacting law of surface defects changing with the cutting parameters are researched. This study is anecessary complement to the surface integrity and the achievements are of greatsignificance to improve the surface quality and to optimize the cutting processparameters.