Effect Of V₂O₅ On The Wettability Of Vitrified Bond And Diamond Abrasive

Vitrified diamond composites have the advantages of high machining quality and less grinding heat can thus be widely used in the precision machining of cemented carbide materials,optical glass,industrial ceramics,and other materials.However,most diamond abrasives have a smooth surface and low chemical activity,which leads to poor wettability between vitrified bond and diamond abrasive,and diamond easily falls off in advance during grinding,thereby violently reducing the service life of the grinding wheel.In order to improve the wettability of vitrified bond to diamond and the mechanical properties of diamond composite,this paper makes an in-depth study on the modification of vitrified bond and diamond,Results are as following:1)V₂O₅was added into the vitrified bond formula,and the results showed that:The refractoriness of the vitrified bond with 4 wt.%V₂O₅reached 555°C,17°C lower than that of the vitrified bond without V₂O₅.During sintering,vanadium ions in the bond was enriched on the diamond surface and combined with the unsaturated carbon atom existed on the surface of diamond to form V-C bond,which can improve the wettability between vitrified bond and diamond abrasive.The wetting Angle decreases with the increase of V₂O₅content,when the content of V₂O₅was 4 wt.%,the wetting Angle was the smallest and the wettability was the best.Li₂Si₂O₅p Hase began to precipitate in bond when addition of V₂O₅content reached 2wt.%.As the amount of V₂O₅increased,the crystals grew rapidly.When the amount of V₂O₅added was 4 wt.%,cracks appeared at the interface between the crystal and the bond.;The Flexural strength and Rockwell hardness of the composites with 2 wt.%V₂O₅were significantly improved from 83.7 MPa and 87.4 HRB to 112.6 MPa and 108.1 HRB,34.5%and 23.7%higher than those of diamond composites without V₂O₅,respectively.2)A V₂O₅thin film was prepared on the surface of diamond to improve the wettability of vitrified bond to diamond and the properties of diamond composite by sol-gel method.The results showed that V₂O₅sol was prepared by melt quenching.When the mass ratio of H₂O/V₂O₅was 50,the melting temperature was 850°C and the holding time was 20min,the sol was best.a uniform and compact V₂O₅film formed on the diamond surface at a temperature of 600°C by heat treatment when V₂O₅sol had a viscosity of 2 m Pa·s.During the process of heat treatment,the unsaturated carbon atoms on the diamond surface combined with V₂O₅film to form O-V-C and V-O-C bonds.During the sintering process of vitrified diamond composites,V₂O₅film on the diamond surface dissolved in the vitrified bond,which would reduce the surface tension and refractoriness of vitrified bond at the interface,and improve the wettability of vitrified bond to diamond.When the sintering temperature was at650°C,the flexural strength and rockwell hardness of the diamond composites coated with V₂O₅film were 92.8 MPa and 99.4 HRB,which are about 8.4%and 13.5%higher than those of the uncoated composites at 85.6 MPa and 87.6 HRB,respectively.3)The performance of the diamond grinding wheel prepared by adding 2 wt.%V₂O₅to the vitrified bond was improved,The roundness and straightness errors of the 50^thzirconia workpiece in one dressing cycle decreased from 3.31 and 2.11?m to 3.02 and 1.9?m,respectively,as compared with the vitrified diamond wheel without V₂O₅.The grinding performance of the grinding wheel prepared by the diamond coated with V₂O₅film was obviously improved.Compared with the uncoated sample,the roundness and straightness errors of the 50^thzirconia workpiece decreased from 3.35m and 2.14m to 3.13m and 1.99m respectively in one dressing cycle.