Strengtenhing And Toughening Of Vitrified Bond With Nano Rare Earth Oxides For Cubic Boron Nitride Grinding Wheel

Vitrified bond binded-cubic boron nitride(cBN)grinding wheel is restricted for wider applications due to the high brittleness,this papper therefore selects the wellperformed vitrified bond as the based vitrified bond by comparing the quality of various vitrified bonds,and try to add rare-earth oxides in nanoscale size to enhance the tougheness of vitrified bond,such as cerium oxide,oxidation samarium,yttrium oxide,lanthanum oxide and erbium oxide.In order to obtain the optimum composite vitrified bond,the type and the content of rare-earth oxides adding into the vitrified bond were investigated respectively.Thereafter,the optimum composite vitrified bond mixed with cubic boron nitride was sintered.X-ray diffraction(XRD),Scanning Electron Microscope(SEM),Differential Scanning Calorimetry(DSC)and thermal dilatometer were deployed to analysize the phase,microstructures,thermal effect and coefficient of thermal expansion.And three-point bending and single edge notch beam were applied to measure the bending strength and fracture toughness.The experimental results show that sintering temperature of selected based vitrified bond is within a range of 670 °C to 700 °C,the maximum bending strength and the fracture toughness are 165 M Pa and 1.3 MPa?m1/2,respectively.Besides,vitrified bond sintered with c BN shows good wettability;Rare-earth oxides have no effect on the main phase composition of vitrified bond;Grains of based vitrified bond is refined when adding 2 vol.% of lanthanum oxide or 2 vol.% of erbium oxide,which is attributed to the improvement of bending strength reaching The maximum bending strength is 187 MPa when adding lanthanum oxide and the maximum bending strength is 194 MPa when adding erbium oxide,compared with that of the based vitrified bond,each of the bending strength value increased by 13.3% and 17.6% respectively.Adding all of these five kinds of rare-earth oxides can be implemented on toughening the based vitrified bond,among which toughening effect of adding erbium oxide is the most effective,when the adding 2.5 vol.% content,the fracture toughness is 2.7 MPa?m1/2,in comparison with the based vitrified bond,which increased by 108.2%.Erbium oxideadded vitrified bond mixes with cBN,concentration of cBN grinding tool in control at 200%,the experimental results show that the composite vitrified bond has good wettability with cBN,and the bending strength is 102 MPa.