Effect of Vitrified Bond on the Performance of Diamond Grinding Wheel

Compared with metal bonded abrasive tools and resin bonded abrasive tools, ceramic bonded superhard material grinding wheels have the advantages of good heat resistance, porous structure for easy heat dissipation, easy chip removal, small grinding elastic deformation, high grinding accuracy, good self-sharpening, etc., and are widely used in various industries. The performance of ceramic bonded abrasive tools depends largely on the performance of ceramic bond, and the performance of ceramic bond is related to its composition and preparation process.

 

As a commonly used diamond abrasive in the superhard material industry, it has poor high temperature resistance, so the required binder should have a low sintering temperature and suitable fluidity and thermal expansion coefficient. R2O- Al2O3-B2O3- SiO2 system is a common ceramic binder system for diamond grinding wheels. Different components have different effects and have different effects on the performance of abrasive tools.

 

We conducted sintering analysis by changing the content of Al2O3, B2O3 and SiO2 in the binder, and explored the influence of different component contents on the various properties of the binder, in order to provide some valuable guidance for everyone to use ceramic binders and improve the performance of diamond grinding wheels.

 

1 Refractoriness analysis of binder

The refractoriness of binder is a performance index that directly affects the firing temperature of abrasive tools. B2O3 has the effect of reducing the refractoriness in ceramic binder, while SiO2 and Al2O3 in ceramic binder will increase the refractoriness of binder, and the effect of Al2O3 on the refractoriness of binder is greater than that of SiO2.

 

 

2 Fluidity analysis of binder

Fluidity of binder is a parameter that reflects the viscosity change of binder in high temperature molten state. The higher the fluidity of binder, the better its bonding performance with abrasive. B2O3 has the effect of improving the fluidity of binder in ceramic binder, while Al2O3 will reduce the fluidity of ceramic binder.

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3 Analysis of thermal expansion coefficient of binder

In order to make the ceramic binder and abrasive have better holding force during sintering and avoid thermal stress between the binder and abrasive interface, the thermal expansion coefficient of the ceramic binder needs to match the thermal expansion coefficient of the abrasive. The thermal expansion coefficient of the ceramic binder is determined by the content of each component and the network structure formed. When the molar ratio of Al2O3 + B2O3 and Na2O in the binder is n(Al2O3 +B2O3) / n(Na2O) <1, Al2O3 and B2O3 will combine with the oxygen ions in Na2O to form [AlO4] and [BO4], and participate in the network structure of the binder, making the network structure of the binder denser, thereby reducing the thermal expansion coefficient of the binder; when n(Al2O3 + B2O3) / n(Na2O) > 1, the oxygen ions in Na2O are insufficient, Al2O3 and B2O3 form [AlO3] and [BO3] triangles, which reduces the density of the network structure and causes an increase in the thermal expansion coefficient.

 

Affected by the combined contents of Al2O3, B2O3 and SiO2, the increase of Al2O3 and SiO2 contents can usually improve the flexural strength of the binder, while the effect of B2O3 varies with the content of Al2O3.

 

4 Microhardness analysis of binder

When the mass fraction of SiO2 is 65%, the mass fraction of B2O3 in the binder increases from 10% to 25%, and the microhardness of the binder increases by 35 MPa; when the mass fraction of Al2O3 is 15%, the mass fraction of SiO2 in the binder increases from 15% to 30%, and the microhardness of the binder increases by 60 MPa; when the mass fraction of B2O3 is 20%, the mass fraction of SiO2 in the binder increases from 55% to 70%, and the microhardness of the binder increases by 93 MPa. Therefore, it can be inferred that the influence of each component on the improvement of the microhardness of the binder is SiO2> B2O3> Al2O3.

 

 

 

The ceramic binder used in diamond grinding wheels often has as few as five or six components, and as many as more than ten. According to the glass network theory, each component is divided into network formers, network modifiers, and network intermediates, with different functions and influences. Most of the professional research on ceramic binders in the superhard products industry is in colleges and universities. Due to the complexity of glass, even the theory of glass formation has not been determined yet. In addition, the importance of its performance, the research value is still very large. As you can see, there are many research results on different glass systems and different components in colleges and universities, but there is another indisputable fact: most superhard product manufacturers lack relevant research and have been sticking to one or two ceramic binders for many years, resulting in a difficult qualitative breakthrough in grinding wheel products.