Study On Performance Of Vitrified-metal Composite Bond CBN Grinding Wheels Fabricated By Melt Infiltration Process

The vitrified bond CBN grinding wheel has the advantages of high elastic modulus and low grinding force,which is often used in ultra-precision grinding of metal materials.However,due to the low impact toughness of vitrified bond,the grinding wheel has the problems of poor shape retention and low service life in the forming grinding of high-strength and high-toughness metal materials.Therefore,this paper first developed the vitrified bond with high mechanical properties and good interfacial wettability with CBN abrasive and prepared porous vitrified bond CBN preform.Then,the vitrified/metal bond CBN grinding wheel was prepared by infiltration method with Cusn₃₃as infiltrating agent.Finally,the vitrified/metal bond CBN grinding wheel was applied to the cylindrical groove grinding of INCONEL713nickel-based superalloy,the conclusions are as follows:（1）When the amount of TiO₂was 6wt.%,the thermal expansion coefficient of the vitrified bond was 4.6544×10^-6℃^-1,which matched best with the thermal expansion coefficient of CBN,and the fibrous rutile microcrystals began to precipitate in vitrified bond.With the increase of TiO₂content,the flexural strength of the vitrified bond increased rapidly due to the dispersion strengthening effect of microcrystalline.When the TiO₂content was 10wt.%,the flexural strength reached the maximum value of 118.19MPa,which was 27.22%higher than that of the formula without TiO₂.（2）With the continuous addition of TiO₂,the flexure strength and hardness of the vitrified CBN composites increased first and then decreased.When the TiO₂amount was 6wt.%,the flexure strength and hardness reached the maximum values of 116.18MPa and 128 HRB,which were 48.49%and 34.74%higher than those of the basic-formula bond CBN composites without TiO₂,respectively.During the sintering process,the vitrified bond could form the strong Ti-B chemical bond with CBN abrasive at the bonding interface,which greatly improved interfacial wettability between the CBN abrasive and the vitrified bond,and improved the mechanical properties of vitrified bond CBN composites.（3）When the pore former content was 20wt.%,the continuous interpenetrating pore structure was formed in the porous preform,and the infiltration effect was obviously improved.The interstitial rate of the Cu Sn₃₃infiltration phase reached up to54.25%.Meanwhile,adding 15vol.%infiltration enhancer to the porous body could significantly improve the interfacial wettability between the porous body and the infiltrated metal,and the interstitial rate reached up to 74.62%.（4）The grinding test results showed that the shape retention of the vitrified/metal bond CBN grinding wheel had been significantly improved due to the toughening and strengthening effect of the infiltration metal.The maximum peak-to-valley value of the surface morphology of the processed workpiece was 3.15μm,which was about49.94%lower than that of the pure vitrified CBN grinding wheel,and the service life was about 2.3 times that of the pure vitrified bond CBN grinding wheel.