Experimental Research On Cutting Process Of PCBN Tools Turning Nickel-Based Superalloy

The nickel-based superalloy GH4169can work under high temperature, oxidation and corrosion condition, and has been widely used in aviation and aerospace industries. But this kind of maetrial is considered to be one of the most difficult-to-machining material because of its worse cutting performance. During the process of turning GH4169, it is easy to generate burrs in both sides of chip due to the chip’s plastic side flow under high temperature, and also easy to appear sawtooth chip. Both chip burrs and sawtooth chips can effect the cutting tool life. To solve this problem, some experimental researches were carried out as followed in this paper.First, the orthogonal cutting experiment of GH4169using PCBN tools was implemented. By measuring the cutting force, the width of chip and observing the chip morphology, some conclusions were drawed:the cutting force showns a trend of first increased and then decreased as the cutting speed increases; there is a positive correlation between cutting force and feed; as the feed, tool flank wear and negative chamfering angle increase, the chip width are increased and more chip burrs are generated, and thus the phenomenon of chip side flow is more and more serious; with the increase of cutting speed, the chip side flow phenomenon abates gradually, and when the speed increases to62.4m/min, it starts to keep steady; cutting tool’s materials and egde radius almost have no impact on chip side flow.Then, the investigation was conducted on the chip formation process when turning GH4169and some conclusions were drawed through the observation of chip microstructure using the metallographic microscope:as the cutting speed increases, the chip morphology has in turn experienced three types which are the ribbon chip,the critical sawtooth chip and the sawtooth chip:with the increase of feed and the cutting depth, the segment degree of sawtooth chip is intensified; adiabatic shear theory is considered to be the mechanism of the sawtooth chip formation.Finally, the investigation was conducted on the tool wear when using PCBN tools to cut GH4169. By comparing and analysing the tool life under different conditions, it can be concluded that the tool life at low cutting speed (v=33.8m/min) is four times at high cutting speed (v=121.7m/min);DBW85with-28°chamfer is the best cutting tool to turing GH4169and the wet cutting can improve tool life about2times.The experiment observations show that the main wear forms of tool are rake face wear, flank wear, groove wear and tool fracture, and groove wear is most significant. Using EMS and X-ray spectrometer analysis.it is considerd that the reasons of tool wear are abrasive wear.adhesive wear, diffusion wear oxidation and phase transition wear.and at high cutting speed oxidation wear is more significant. Under different cutting conditions,all of the wear reasons both exist and have a mutual influence each other.