Fabrication And Performance Of Porous CBN Grinding Wheel With Three-dimension Controllable Grain Arrangement

Cubic boron nitride(CBN) grinding wheels, as the executor and tool guarantee, play an important role in removing materials efficiently in grinding high strength and toughness materials, such as nickel-based superalloy. In the present days, the imbalance of porosity and strength of multilayer grinding wheels, and the short life of monolayer counterparts as well, has become the barrier to further improve the performance of CBN grinding wheels.In the current investigation, The porous metal-bonded CBN grinding wheels with three-dimension controllable grain arrangement is developed. The strength and microstructure of the porous metal bond, the design and fabrication technology of the grinding wheel and the grinding performance and wear characteristic of this new type wheel are studied.The main work and results are summarized as follows:(1) The influence of the alumina bubble particles on the strength and microsturcuture of the porous metal bond is investigated. The results obtained demonstrate that the strength and pore structure of the metal bond could be controlled by adjusting the size and volume fraction of alumina bubble particles. The strength of the porous metal bond is higher than 60 MPa when the content of alumina bubble particles is lower than 50 vol.%, which could fulfil the requirement of the grinding wheels used in high-efficiency grinding. In addition, little effect is taken on the bonding interface between CBN grains and the metal bond caused by the alumin bubble particles.(2) The fabrication techonolgies of the grinding wheel, such as the design of the wheel matrix structure, the selection of the abrasive layer texture and the realization of the three-dimension controllable grain arrangement, is investigated. The grinding performance of the porous CBN wheel is evaluated in high-efficiency grinding of GH4169 nickel-based superalloy. The grinding force, grinding temperature and specific grinding energy are discussed. The energy partion transferring into the workpiece is studied. The results display that, during high-efficiency deep grinding with the porous CBN wheels, 2%~6% of the total heat transfers into the workpiece, which is generally lower than the vitrified bonded grinding wheels(4%~8%).(3) The wear of the porous CBN grinding wheel is investigated. With the material removal volume increases, the grains in the grinding wheel surface mainly experience attrition, fracture and then dislodge. The grinding force, grinding temperature and the number of the dislodged grains are characterized by a slowly increase at the primary steady wear stage and a rapid increase in the later wear stage. Most grains at the surface of the grinding wheel dislodge because of attrition and fracture wear and the metal bond is adhered by the ground workpiece material when the material removal volume is beyond 16000mm3.