| The vitrified bond cBN abrasive tool has many outstanding advantages,such as good chemical stability,wide grinding fields,high machining accuracy,sharpness and self-sustaining.It is easy to be reused after dressing and has great economic benefits.It has unique advantages in grinding materials of difficult machinability.However,High speed,high efficiency and high precision grinding in aerospace,shipbuilding and machine processing and other aspects need to be improved,the traditional vitrified abrasive performance is still not enough to meet the requirements of modern manufacturing.Thus,it is imperative to develop cBN ceramic abrasives with better performance.Developing high performance ceramic binder is the most important.This thesis mainly discussed the preparation and performance of nano ceramic binder for cBN abrasives.Based on R2O-RO-Al2O3-SiO2-B2O3 system,the properties of the ceramic binder are improved by adding a certain amount?mass percentage?of nano-additives?titanate nanowires,titanium oxide nanowires and titanium oxide nanoparticles?.The properties of ceramic binders and cBN abrasives were studied by electronic multifunction tester,differential thermal dilatometer,microhardness tester,Rockwell hardness tester,friction and wear tester,X-ray powder diffraction?XRD?,energy spectrometer and scanning electron microscope?SEM?.After a series of tests and analysis,the action mechanism of additives on ceramic bond is analyzed.The performance of two kinds of binder cBN grinding tools was compared,and the influence of sintering temperature on two kinds of grinding tools was discussed,and the high performance c BN grinding tools were prepared.The results show that:?1?When the adding content of titanate nanowires was0.5wt%,the performances of vitrified bond were improved.The thermal expansion coefficient of ceramic binder was reduced,and its flexural strength,microhardness and fluidity were improved.The thermal expansion coefficient was 5.72×10-6?-1.the bending strength and microhardness were 76.29MPa,846.23MPa.And the fluidity was136.8%.?2?When the adding content of titanium oxide nanowires was 0.2wt%,the performances of vitrified bond were the best.The thermal expansion coefficient of ceramic binder was reduced,and its flexural strength,microhardness and fluidity were improved.The thermal expansion coefficient was 5.37×10-6?-1.the bending strength and microhardness were 85.96MPa,853.19MPa.And the fluidity was 140.6%.?3?When the adding content of titanium oxide nanoparticles was 0.2wt%,the performances of vitrified bond were improved.The thermal expansion coefficient of ceramic binder was reduced,and its flexural strength,microhardness and fluidity were improved.The thermal expansion coefficient was 5.89×10-6?-1.The bending strength and microhardness were 65.24MPa,839.87MPa.And the fluidity was 129.1%.?4?The effects of three additives on the structure and properties of ceramic bonds were comprehensively compared.It was found that the ceramic bond with 0.2wt%titanium oxide nanowires had the best performance.And,it was used for comparison between cBN Abrasives preparation and ceramic binder cBN ceramics without addition.The flexural strength of cBN abrasives with 0.2wt%titanium oxide nanowires was63.27MPa,and the flexural strength?45.02MPa?of the base ceramic binder was 40.5%higher than that of the base ceramic binder.The Rockwell hardness was 61.5HRB,and the cBN grinding tool?48.5HRB?was 26.8%higher than that of the base ceramic binder?48.5HRB?;The porosity of the grinding tool was reduced to 48.9%.The grinding ratio was 22.3,and the base ceramic binder?15.1?was improved by 47.7%,and the overall performance of the grinding tool was improved. |
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