Study On Preparation And Grinding Properties Of Vitrified Bond Diamond Wheel

Contraposing the current development and existent issues of the vitrified bonddiamond wheel, the main researches of this paper were focused on the preparation ofthe high-performance diamond wheels’ vitrified bond and systematically discussed theeffects of the components of the vitrified bond on the vitrified bond’s performance.Originality, with the TiO₂sol as the film medium, the diamond abrasive surface wascoated with a compact TiO₂film by Sol-Gel technology, which actualized themodification of the diamond surface with the inorganic membrane. After optimizingthe components of the vitrified bond diamond wheels and the preparation technology,the vitrified bond diamond wheels were prepared and applied to grind the excircle ofthe monocrystalline silicon. The effects of the grinding parameters on theperformance of the grinding wheels were investigated.This paper was first researched on the preparation of the vitrified bond. It wassystematically discussed the effect of the varieties and contents of the alkali metal onthe vitrified bond’s refractories, bend strength, expansion coefficient, water resistanceand the effect of the wettability of the fusion vitrified bond on the diamond in thesystem of R2O-Al₂O₃-SiO₂-B₂O₃vitrified bond. Through the experiments, it hadfirstly proved that the double alkali would have great influence on the performance ofthe vitrified bond and expounded the mechanism. It had been introduced thehighoxide ZrO₂and discussed the effect of the content of ZrO₂on the performance ofthe vitrified bond. When the ZrO₂content was less than2mol%, the Zr⁴⁺would enterinto glassy network as mending nets and agglomeration composition. With theincreasing of ZrO₂, the vitrified bond’s refractoriness, bent strength, water resistance,and expansion coefficient were decreased. It was also found that the wetting anglebetween the vitrified bond and diamond got small for enrichment of Zr⁴⁺on diamondsurface. When ZrO₂content was more than2mol%, there was a little of ZrO₂existingin vitrified bond as ZrO₂particles, playing the role of nucleating agents andpromoting the separation of spodumene.In consideration of improving the interface bonding strength between thediamonds and the vitrified bond, the diamond abrasive surface was originality coatedwith a compact TiO₂film by Sol-Gel technology. This paper was first discussed thefilming mechanism of the TiO₂sol coating on the diamond’s surface, the interface structure and the bonding situation between the TiO₂film and the diamond, and thevariation in properties of the TiO₂film coated diamond. The results were showed thatthe TiO₂film was beneficial to the inoxidizability of the diamonds, as the uncoateddiamonds started oxidation was at687℃in the air flowing while the diamondscoating TiO₂film three times was at762℃.During the process of sintering with thevitrified bond, the TiO₂film coating on the diamond’s surface was slowly spreaded inthe vitrified bond, formed the transition layer between the vitrified bond and thediamonds, and improved the holding force between the vitrified bond and thediamonds.The vitrified bond diamond wheel was prepared by the traditional pressingsintering method. It was systematically researched on the effects of the coateddiamonds, the particle size, the content of vitrified bond, the sintering process, thetype and the content of the pore-forming material on the performances of the vitrifiedbond diamond wheel.Abrasive size had great effect on diamond wheels performance:putting the vitrified bond content as a constant24wt%, for un-coating diamond wheels,when diamond abrasive size was140/170#, the bent strength and hardness of wheelsreached its max value,77.2MPa and HRB102.8, on the other hand, when diamondabrasive size was120/140#,the wheels’ grinding ratio for grinding monocrystallinesilicon at its max value981.6; for coating diamond wheels, following theincreasement of diamond size the bent strength and hardness was put on, whendiamond abrasive size was100/120#,the wheels’ grinding ratio for grindingmonocrystalline silicon at its max value1728.1. The content of the vitrified bond hadalso great effect on diamond wheels performance: when the diamond abrasive sizewas140/170#, at the vitrified bond content26wt%, for un-coating diamond wheels,the bent strength, the hardness and the grinding ratio of the wheels reached its maxvalues,80.1MPa, HRB105.4,902, respectively. However, for the coating diamondwheels, following the increasement of the content of vitrified bond, the intensity andthe hardness of the wheels was increased and the grind ratio was decreased. At thevitrified bond content26wt%, the wheels’ grinding ratio for grinding monocrystallinesilicon at its max value1421, the surface roughness Ra of monocrystalline silicon wasminimum,0.32.Pore-forming agent content had great effects on diamond performance:with the increasing of pore-forming agent content, the wheels’ bent strength andhardness were reduced while the grinding efficiency and surface roughness wereincreased。 Adding the same content pore-forming agent, the surface roughness Ra ofmonocrystalline silicon that was grinded by adding naphthalene wheels was lower. When the vitrified bond diamond wheels were prepared and applied to grind theexcircle of the monocrystalline silicon, it was found that the grinding ratio of thevitrified bond diamond wheels was close to the metal bond diamond wheel. After theprocess of the grinding, the surface roughness Ra of monocrystalline silicon wasreached the requirements, which was not the corrosion of HF.The grinding parameterhad great effects on the performance of the diamond grinding wheels. The relationshipbetween grinding parameters and grinding wheels performance was showed that:when the cut depth was constant, as the grinding wheels speed turning faster, thetangential grinding force was smaller, so the speed of diamond abrasive falling offwas slower, thereby the grinding ratio on monocrystalline silicon increased andsurface roughness Ra of monocrystalline silicon reduced. Under the condition thatgrinding speed was constant, for the grinding wheels prepared by the uncoateddiamonds, the grinding ratio reduced with the increasing the cut depth. And there waslittle fluctuation on surface roughness. The diamond fell off from the grinding wheelin form of the whole-grain.But,for the TiO₂film coated diamond, with the increase ofcut depth, the mode of diamond fell off turned whole-grain type to breakage type.Compared with the uncoated diamonds, the grinding ratio on monocrystalline siliconwas smaller and surface roughness Ra value improved.Dressing cycle also affectedthe performance of wheels’ grinding. The dressing cycle was shorter; the grindingwheel was sharper. And the power output by spindle motor was smaller thereby thegrinding ratio of the grinding wheel was also smaller.