Effect of composition and content on properties of vitrified bond
Objectives:Vitrified bonded diamond grinding tools are widely used in the machining industry,but the high-temperature resistance of diamond is poor.Therefore,there are high requirements on sintering temperature,flowability,and thermal expansion coefficient of vitrified bond materials.The influence of the content of Al2O3,B2O3,and SiO2 in vitrified bond on its properties is investigated.By changing the content of these three components and comparing the changes in the properties of the bonds,a more suitable vitrified bond for diamond grinding tools is obtained.Methods:Using a ternary phase diagram,the content of Al2O3,B2O3,and SiO2 in the R2O-Al2O3-B2O3-SiO2 bond system is adjus-ted.Sixteen different formulas were designed to prepare 5 mm×6 mm×30 mm sample strips under a pressure of 5 MPa,and dried at 80℃for 12 hours.The refractoriness of each group of bonds was measured using a standard refract-ory cone,the flowability of the bonds was measured using the plane flow method,and the thermal expansion coefficient of the bonds was determined.According to the refractoriness data determined by each formula,sintering was carried out at a temperature 60℃higher than the refractoriness of the bond.A microcomputer-controlled electronic universal test-ing machine was used to determine the flexural strength of the bond using the three-point bending method.The micro-hardness of the bond was measured using a microhardness tester,and the microstructure of the bond was analyzed.Res-ults:From the analysis of the measured performance data,it can be concluded that:(1)B2O3 has the effect of reducing the refractoriness in vitrified bonds,while SiO2 and Al2O3 increase the refractoriness of the bonds.Al2O3 has a greater impact on the refractoriness of the bonds than SiO2.(2)B2O3 has the effect of improving the flowability of bonds,while Al2O3 reduces the flowability of bonds.The thermal expansion coefficient and the flexural strength of the bond will vary depending on the content of Al2O3 and B2O3.When the Al2O3 content in the bond is high,the thermal expansion coeffi-cient of the bond will first decrease and then increase with the increase of B2O3 content,and the flexural strength will first increase and then decrease with the increase of B2O3 content.When the Al2O3 content in the bond is low,the thermal expansion coefficient of the bond will increase with the increase of B2O3 content,and the flexural strength will decrease with the increase of B2O3 content.When the SiO2 content is fixed,the thermal expansion coefficient of the bond will increase with the increase of B2O3 content,and the flexural strength will increase with the increase of Al2O3 content.When the B2O3 content is fixed,the thermal expansion coefficient of the bond will increase with the increase of Al2O3 content,and the flexural strength will increase with the increase of B2O3 content.The influence of each compon-ent in the bond on the microhardness change of the bond is SiO2>B2O3>Al2O3.When the molar ratio of Al2O3+B2O3 to Na2O in the bond is less than 1,Al2O3 and B2O3 will combine with oxygen ions in Na2O to form[AlO4]and[BO4],which participate in the network structure of the bond and densify it.Breaking the dense network structure requires higher energy.Therefore,densification of the network structure in the bond can reduce its thermal expansion coefficient and improve its flexural strength and microhardness.When n(Al2O3+B2O3)/n(Na2O)>1,the oxygen ions in Na2O are in-sufficient,and Al2O3 and B2O3 form[AlO3]and[BO3]triangles,reducing the density of the network structure.The fluffy structure makes the network structure more sensitive to energy,increasing the thermal expansion coefficient of the bond and reducing its flexural strength and microhardness.Conclusions:A ternary phase diagram based on the content of Al2O3,B2O3,and SiO2 in the R2O-Al2O3-B2O3-SiO2 system bond can intuitively reflect the synergistic effect of the three components during sintering.The three components will exhibit different effects in bonds with different contents,and their impact on the performance of the bond will also be different.When designing the formula for vitrified bonds,it is necessary to consider the roles of different components in the bond and their interactions with other components.
vitrified bond componentsternary phase diagramthermal expansion coefficientmechanical property
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