Research On The Preparation Of Vitrified Bond CBN Abrasive Tools For Double Side Grinding

Vitrifed bond cubic boron nitride (CBN) abrasive tool is becoming one of themost promising tools in double side grinding field owing to its outstanding properties.In this work, the formula and controlled pore morphology of vitrified bond CBNabrasive tools used in double side grinding were investigated. The effects of abrasivegrain size, the content of vitrified bond, molding density, the content and the size ofdifferent pore formers on the properties of abrasive tools were discussed, respectively.The porosity of abrasive tools was determined by the Archimedes method. Besides,the bending strength, Rockwell hardness and microstructures were measured byuniversal testing machine, Rockwell hardness tester and scanning electron microscope,respectively.The results indicated that, for coarse-grained abrasives, the coarser the abrasivegrains, the lower the porosity, bending strength and Rockwell hardness of the abrasivetools. For fine-grained abrasives, the porosity decreased with the increasing abrasiveparticle size, but the bending strength and Rockwell hardness increased firstly andthen decreased. In certain extent, the increasing content of vitrified bond resulted in adrop in porosity and a rise in both bending strength and Rockwell hardness of theabrasive tools. As the content increased further, the bending strength decreasedsomewhat, and the hardness increased slowly. The increasing of molding densityresulted in a drop in porosity and a rise in mechanical strength.Activated carbon, activated carbon/starch composite and polymethylmethacrylate(PMMA) were chosen as the pore formers in the work. The increasing content of poreformer caused a rise in porosity and a drop in both bending strength and hardness,independent of the type of pore former used. The specimen prepared with activatedcarbon showed a mass of irregular pores with various sizes. Its total porosity wasnegligibly higher than those of specimens prepared with activated carbon/starchcomposite and PMMA, while the bending strength and Rockwell hardness wereobviously lower than the other two in the same conditions. The specimen preparedwith composite pore former exhibited the highest hardness. The specimen preparedwith PMMA demonstrated quasi-spherical pores with relatively uniform pore sizedistribution, and highest bending strength. As the size of PMMA increased, the total porosity remained almost unchanged, while the bending strength and hardnessdecreased frstly and then increased.