Study On The Structure And Properties Of Super-high-speed Vitrified Bond CBN Grinding Wheels

Vitrified bond CBN abrasive is suitable for high-speed, high efficiency and highprecision grinding and it is the most important one of the ultra-high speed grinding tools. Theinfluence of modifying of the vitrified bond， the abrasive manufacturing process (includingthe firing temperature and time, forming density and molding process), and the porousformers to the structure and properties of the low vitrified bond and the grinding tool wasstudied by using DTA-TG analysis, X-ray diffraction analysis, testing of the mechanicalproperties and microscopy. And the best formula and process of the super high speed vitrifiedbond CBN abrasive tools was researched.Three kinds of additives, T1, T2and T3, were added in R2O-B2O3-Al2O3-SiO2system inorder to improve the flowability of the vitrified bond and its wetability to the abrasives.Thereby interfacial adhesion of the bond and the abrasives could be improved. The threekinds of additives all can reduce the softening temperature of the vitrified bond, and improveits liquidity. The adding of T1and T2can improve the mechanical properties of the bond, andthe effect of performance improvement of T2is most apparent. When the mass fraction of T2is6%, the bond has the best mechanical properties. The flexural strength is64.95MPa, andthe microhardness is752.73MPa. T3can induce coarse grains in the vitrified bond, andreduce the mechanical properties of the bond. The effect of Additives on the mechanicalproperties of the abrasive is not entirely consistent with the impact on the bond. T3cansignificantly improve the liquidity of the bond, which is beneficial to the interfacial bondingof the bond with the abrasives. Thus the mechanical properties of the abrasive tool can beimproved. When the mass fraction of T3is2%, the mechanical properties of the abrasiveachieve the maximum value. The bending strength is57.89MPa, and the Rockwell hardness is104.7HRH. Compared with the abrasive samples without additives, which are produced at thesame sintering process parameters, they are respectively improved18.24%and12.22%. Through the study of the process parameters, the results show that the abrasive sampleshave the best overall performance when the firing temperature is840℃, heating time is150min, the preformed density is2.4g/cm3, and the forming technology is cold isostaticpressing. At this point, the bulk density, the flexural strength and Rockwell hardness of thesamples reach the maximum, which respectively are2.57g/cm3,87.61MPa and120HRH. Atthis time, the porosity of the abrasive is18.54%.Three types of porous formers A1, A2, A3, B, C1, C2, C3were added in abrasive toolsin order to improve the porosity, pore size and its distribution in the abrasive. The sampleswith addition of A1and C1, have the uniform pore distribution. And compared with thesamples without the pore-forming agent, the decrease of their bending strength is not obvious.The pore forming effect of A1is better than C1, but C1can increase the impact toughness ofthe specimens. When the mass percentage of C1is8%, the abrasive specimen has the bestintegrated performance, the distribution of the pore is uniform, the porosity is30.82%, thebending strength is49.89MPa, and the impact toughness is1.73KJ/m2.