Structure Regulation For Vitrified Bonded Diamond Tools

Vitrified bonded diamond tools has strong grinding force.Under grinding,the temperature of the tool is low.The wear and tear of the tool is low.When grinding,the tool keeps good shape stability.The tool can repair by itself easily.Compare with metal bonded diamond tools and resin bonded tools,vitrified bonded diamond tools are used less.During the synthesis process of the vitrified bonded diamond tools,the shrinkage of the tools was inevitable.But the huge shrinkage was detrimental to the properties of the diamond tools,which makes the strength declined since the cracks and stress occurred.In addition,there is more workload added during the dressing process,resulting in the production efficiency declined.Therefore,the little shrinkage of tools is better.In this work,when the tools has no shrinkage was experimentally explored.The low-temperature vitrified binders were selected since the diamond was prone to oxidization while the atmosphere temperature was up to 800?.Based on the main constitute of SiO₂?Al₂O₃?K₂O and Na₂O,the bonders named N68,N73 and N78 were produced by self-developed.The refractoriness of the them were 680,730,and 780?,respectively.Two different diamond grits with US meshes from 230 to 270?low-grade RVD and a high-grade MBD-6?were used in this work.The samples are prepared through the cold press sintering.The results showed that the shrinkage of the tools was declined with the content of the diamond grits rising.When the RVD diamond was in the percent of 47.5vol.% and the MBD-6 diamond was in the percent of 52.5 vol.% the tools had no shrinkage.Some pores appear when the percent of diamond beyond the 47.5 vol.% or 52.5 vol.%.With the increasing of the amount of diamond,the porosity decreased.With the increase of the amount of diamond,the flexural strength decreased.Begin with the appearance of pores the bending strength decreased.To avoid diamonds taking off from the tool early we tried a series of experiments.Trough grinding the bonder became more fine.The flexural strength of the tools improved by 36.4%,16.1%,26.4%.In this paper,through water vapor etching made the surfaces of diamonds rough.There was the water gas reaction between carbon and water vapor.Compare with the etching of the strong oxidizing reagents?such as KNO₃,HClO₄,KMnO₄ e.g?,this method has non-polluting and high safety.The RVD diamond can be etched well by water vapor under 900° C for 30 minitues.The MBD-6 diamond can be etched well by water vapor under 900° C for 60 minitues.After the etching of the diamond,its holding force in vitrified bonder increase obviously.In the same proportion the flexural strength value of the diamond tool increased which improved 3.8% to 8.5%.for the original sample.