Study On The Bond Of PCBN Cutting Tool Used For Cutting Titanium Alloy

Aiming at resolving the problem of hard machining of titanium alloy, this paperinvestigates the interacting rules among some PCBN bonding formulas, its cutting toolperformance and its wears through analyzing and comparing the different bondssynthesized PCBN bars under HTHP，making different cutting tools and the tests ofTi-alloy cutting.Firstly this paper introduces the characters of Ti-alloy cutting and its hardprocessing, summarizes the current situation of the development of PCBN cutting tool,and the products wide used. Subsequently different bonds for PCBN have designed,which was suit for machining titanium alloys by theory. This paper researches andanalyzes the performance of PCBN which synthesized by CBN powder and bond underhigh temperature and high pressure. The synthetic parameters such as heatingpower,synthetic pressure and heat preservation time were explored and beoptimized.Finally, this experiment makes out the best technique parameters are heatingpower7kw, synthetic pressure was70Mpa, heat preservation period12min. Based onthese parameters PCBN bars with different metal bonds, ceramic bonds, metal ceramicbonds synthesized. Furthermore by testing its microhardness and the abrasion ratio,observing the phase composition and microstructure by XRD, SEM， the relationshipbetween the phase composition, microstructure and the performance of PCBN has beenrevealed.Under this process, the performance of PCBN with metal bond and metalceramic bond was better than the performance of PCBN with pure ceramic bond. Themetal aluminum powder plays an important role in the sintering process, there is noreaction between ceramic bond and CBN under this process, and there was no newphase formation, the performance of PCBN can be improved by increasing the heatingpower to some extent.Through processing of making acceptable PCBN bars as lathe bit and to turn titanium alloy TC4with same cutting tool parameter and same turning feed, the resultsshow that cutting performance of PCBN with metal bond is the best as well as surfacequality of the workpiece. The cutting performance of ceramic bond PCBN lathe bit isthe worst. The life of PCBN bit which contains titanium bond was the shortest, in theprocess of cutting, stick knife phenomenon of this PCBN bit is serious. The wear ofPCBN tool mainly occurs in the flank surface of cutting tool, cutting edge or point ofthe tool. There is less wear and tear in the rake face of the tool. Analyzed by the SEMand EDS methods, the main wear mechanisms involve in mechanical wear, adhesivewear, adhesion wear, oxidative wear and diffusion wear. Adhesive wear is the mostobvious and the most serious among them. The life of the cutting tool would beextended if reduced the cutting speed.