Preparation And Microstructure Control Of Nanocrystalline Corundum Abrasive

Ceramic corundum abrasive is a new alumina-based abrasive . It is a promisingabrasive of high performance due to excellent self-sharpening, high precision grinding ,lower grinding cost and long service life in superior machining field , as compared tothe conventional single crystalline fused-corundum abrasive. In the present workmorphology-controlled ceramic corundum abrasives were prepared by pressurelesssintering based on the sol-gel technology. The influences of no additives and nano Alpower, SiO₂, CaO, MgO, B₂O₃, fluoride, Fe₂O₃ and CoO single phase additives andtheir multiphase additives on the microstructure and mechanical properties wereinvestigated. The effects of different additives, additives proportion and sinteringprocess on the microstructure and single particle compressive strength were analyzedsystematically by SEM and diamond single particle compressive strength tester．The results showed that the samples with additives had higher single particlecompressive strength and denser microstructure than that without additives. Themicrostructure of samples was more dense, the single particle compressive strengthwas higher. The single particle compressive strength of crystalline grain withequiaxed or spherical microstructure was higher than that with plate-likemicrostructure. Nano Al power, SiO₂, B₂O₃, fluoride, Fe₂O₃ and CoO were conductiveto the formation of axial or spherical ceramic corundum grains and CaO and MgOwere conductive to the formation of plate-like ceramic corundum grains.As the molar ratio of sintering additive s with SiO₂-MgO, SiO₂-MgO-CaO was 2:1and 2:1:1, respectively and the content of fluoride in the CMS-F and B₂O₃ in theCMS-B₂O₃ were both 1.0wt.%, ceramic corundum abrasives with fine grainmicrostructure and high mechanical properties were obtained. The microstructure andmechanical properties of four phase additives containing Fe₂O₃ or CoO was betterthan that with three or two phase additives.The sintering process had a significant effect on the properties of the ceramicalumina abrasive. The best parameters of tra ditional pressureless sintering processwere investigated. The effects of two-step sintering temperature on the microstructureand mechanical properties were also investigated. The two-step sintering of ceramiccorundum abrasive would reduce the abrasive grain size and promote densification of samples at low temperature.The formation mechanism of hexagonal platelets ceramic corundum abrasive waspreliminary studied, assuming that appropriate amount, proportion and uniformdistribution of additives promoted the grain growth as its growth habit.