Preparation And Properties Of Vitrified Bond Superhard Abrasive Composites

Vitrified bond superhard abrasive composites have been widely applied in high-efficiency and high-speed grinding field.However,there are still some problems in the flexural strength,toughness,pore structure,and wettability between diamond and glass bond of vitrified diamond composites.In this work,the effects of fly ash cenosphere,SiCw/SiCw@SiO₂,FA/FA@SiO₂ content on the constitution,microstructure,apparent porosity,fracture strength,as well as Rockwell hardness of the composites were investigated,respectively.The fractal dimension was used to evaluate the uniformity of diamond abrasive distribution;also,the finite element method was employed to simulate the grinding temperature field in a real abrasive distribution wheel model.?1?The porosity,pore shape and size of vitrified diamond grinding wheels were successfully tuned by controlling the content and size of the added fly ash cenospheres.The bending strength decreased exponentially with increasing pore former content and size.According to XRD analysis,the existence of albite implied that a reaction between SiO₂,Al₂O₃ and Na₂O occurred in the sample during sintering.The input parameters and their coupled influences on the open porosity and bending strength were obtained with RSM,and optimized fly ash cenosphere content?4wt%?and size?160?m?were determined for obtaining optimal ceramic bonded grinding wheels.?2?The mechanical behaviour and void structures of the samples were correlated with the microstructure evolution,including the whisker/matrix interaction.When the whisker added fractions were 4 wt%?SiC whisker?and 3 wt%?SiC@SiO₂ whisker?,the flexural strength of the samples reached their maximum values of about 72.13 MPa and71.60 MPa,respectively.?3?An effective and simple St?ber method has been carried out to deposit SiO₂layers on fly ash cenosphere.Compared to the composites using FA as pore former,FA@SiO₂ composites show?i?the improved pore structures,?ii?equally high porosity,?iii?the lower flexural strength loss and?iv?the lower grade loss.These excellent properties are benefited from the FA@SiO₂ core-shell structure.Porous FA@SiO₂specimens presented smooth pores surfaces and good interfacial debonding between FA@SiO₂ and glass matrix,enabling cracks to be stopped at the FA@SiO₂/matrix interface.These core-shell pore formers are promising candidates for applications in the fields of abrasive tools and other related machining tools industry.More details are required in the future regarding its interfacial reaction mechanism as well as its shell thickness related properties.?4?Based on digital image processing technology,the particle size and coordinates of abrasives have been obtained.Fractal dimension results showed that the distribution of abrasive particles was general uniformity.Real distribution diamond wheel with 110abrasives was established by assembly technology of pro/e software.Also,the study presented a finite element model for simulating the temperature field in at different grinding conditions,thus the best grinding parameters?Vs=40.035m/s;ap=400?m?could be defined.