Study On Surface Treatment Of Granular Diamond And Silicon Carbide By Spark Plasma Coating

Due to the small sizes of diamond grits or silicon carbide(SiC)particles in industry,they were always bonded with binders to prepare composites for various applications.But the interface bonding between diamond(SiC)and the binder was poor since they have high interfacial energy with the binder.In this work,preparing coatings on diamond(SiC)by spark plasma coating(SPC)was used to improve the interface bonding between the diamond(SiC)and the binder in composites.The specific research contents were listed as follows:(1)The Ti coatings,Si coatings,Mo coatings,and W coatings on diamond grits were prepared by discharge treatment on the mixture of diamond grits and the corresponding metal powders in SPS system.By controlling the content of metal powders,the mixture could not be sintered as a bulk that they were separated by the standard screen.During the discharge treatment,the chemical reactions were took place at all of the interfaces among Ti,Si,Mo,and W powders and diamond grits.And the coatings on diamond grits were consisted with their related carbides and elements.For the sintered metal-bonded diamond composites,the interface bonding strength between the Ti-coated,Mo-coated,and W-coated diamond grits and Fe-based matrix were improved by 225 MPa,347 MPa,and 499 MPa,respectively.Meanwhile,with the help of the Si coatings,the bending strength and wear resistance of the vitrified-bonded diamond composites were improved by 19.1 % and 23.5 %,respectively.(2)The Ti coatings,Mo coatings,and W coatings on SiC particles were prepared by discharge treatment on the mixture of Si C particles and the corresponding metal powders in SPS system.By controlling the content of metal powders,the mixture could not be sintered as a bulk that they were separated by the standard screen.During the discharge treatment,the chemical reactions were took place at all of the interfaces among Ti,Mo,and W powders and SiC particles.During the discharge treatment,the chemical reactions were took place at all of the interfaces among Ti,Mo,and W powders and Si C particles.And the coatings on SiC particles were consisted with their related carbides,silicides,and elements.With the aid of the Ti coatings,Mo coatings,and W coatings,the interface bonding strength between Si C particles and Fe-based matrix in the composites was improved by 200 MPa,308 MPa,and 401 MPa,respectively.(3)The Mo coatings and W coatings on polycrystalline diamond(PCD)bulks with chemical bonding were also prepared by discharge treatment on the mixture of polycrystalline diamond bulks and the corresponding metal powders in SPS system.In air,the PCD bulks with Mo coatings or W coatings could be brazed on cemented carbide substrate by the brazing alloy as polycrystalline diamond composites.With the aid of the Mo coatings and W coatings,the shear strength between the PCD bulks and cemented carbide substrate was 36.8 MPa and 87.8 MPa,respectively.In addition,the interface bonding strength between the diamond grits and binders in composites was also improved by etching diamond grits,which were etched by high temperature water vapor based on the water gas shift reaction.After etched,the pits on the {111} and {100} surfaces of diamond grits were triangle-shaped and rectangular-shaped,respectively.The bending strength and wear resistance of the vitrified-bonded diamond composites within the ected diamond grits were higher by 12.1 % and 13.9 % than the cases of the ones within the raw diamond grits,respectively.