Fabrication And Wear Of Monolayer Polycrystalline CBN Grinding Wheels Based On Induction Brazing Technology

Polycrystalline cubic boron nitride(PCBN for short)grains are sintered under high pressure and high temperature by using the microcrystalline CBN particles and AlN ceramic binder.PCBN grains remain the outstanding performance of cubic boron nitride(CBN)material,moreover,they could generate sequentially micro-fracture behavior to recover the sharpness of grinding wheel in the grinding process.On the other hand,high-frequency induction brazing could realize high heating efficiency and small shape deformation of the metallic wheel matrix,therefore it becomes a favorable method to achieve a firm bonding between abrasive grain and wheel matrix,especially for the wheels with large dimension and high precision.In the current work,the PCBN grains were utilized to fabricate the monolayer grinding wheel by induction brazing.The reaction mechanism during induction brazing was discovered.The grinding performance and wear behavior of the PCBN wheel were investigated.The outcomes acquired could promote the application of the PCBN abrasive tools in the high efficiency and precision grinding process of difficult-to-cut materials,i.e.nickel-based superalloy.The main work consists of three parts,which are shown as follows:(1)The PCBN grains were brazed to AISI 1045 steel matrix using Ag-Cu-Ti filler alloy based on the high-frequency induction heating technique under different processing parameters.The compressive strengths of brazed grains were measured.Morphology,chemical composition and phase components of the brazing resultants around PCBN grain were also characterized.Under the given experimental conditions,the optimum heating parameters are determined as current magnitude of 20-24 A and scanning speed of 0.5-1 mm/s.(2)The single-layer brazed grinding wheel with PCBN grains was fabricated.The grinding experiments of nickel superalloy GH4169 were conducted in order to test and compare the impacts of grinding parameters on grinding force,force ratio,temperature and specific grinding energy.As a result,the wheel presented good grinding performance,and the change of grinding characteristics was observed.(3)The wear patterns of the brazed PCBN grinding wheel were tested and analyzed,the morphology variation of PCBN grains,the height change of grains,the variation of grinding force and other parameters along with the process of grinding were investigated.All the results indicate that the self-sharpening behavior of PCBN grains helps the grinding wheel retain a stable sharpness level.