Papers by Keyword: Vitrified Bond

Abstract: In this study, a vitrified bond diamond wheel was prepared with alumina bubbles as a pore former. The effect of the size and content of the alumina bubble on the flexural strength, porosity, and hardness of the prepared wheels has been studied. The results showed that the porosity of the grinding wheel samples increased with the rise of the content of the alumina bubble. The porosity of the grinding wheel with finer alumina bubbles is higher than that of the coarser one. The hardness and flexural of the samples with finer alumina bubbles are lower than those with the coarser ones. The research result shows that the content and the size of the alumina bubble have a great influence on the flexural strength and hardness of grinding wheel samples.

Abstract: To investigate the effect of Li₂O, K₂O and ZnO on SiO₂-Al₂O₃-B₂O₃-Na₂O vitrified bond for CBN grinding wheels, the refractoriness and fluidity of specimens with different additions were studied. The bending strength was measured by three-point bending tester and the microstructures were observed by super Depth-of-Field microscope. The results show that Li₂O, K₂O and ZnO can reduce the refractoriness and increase the high-temperature fluidity. Li₂O and K₂O make a contribution to improving the bending strength; however ZnO is harmful to specimens’ mechanical property. Additionally, the fluidity is important to control the number of gas bubbles in specimen according to the microstructure analysis.

Abstract: Wetting agent plays one of the most important roles in matrix designing of vitrified bond tools. In this paper, we studied the impact of wetting agents, resin liquid, sodium silicate and dextrin liquid, in different types and amount on the formability and bending strength of abrasive tools. It shows that tools using resin liquid as moistening agent by adding 4wt%～5wt% of the amount of bond and diamond to forming materials has the best performance in formability and bending strength of green and finished abrasive segment.

Abstract: A kind of vitrified bond was selected to be sintered with diamond powders to prepare diamond abrasive. The effect of the additive of CeO2 and sintering parameters on the performance of vitrified bond diamond abrasive was investigated. The mechanical properties of diamond abrasives were tested on ZMC-Ⅱ type diamond static strength tester and the interfacial bonding states between diamond powders and vitrified bonds were studied by Scanning Electron Microscopy (SEM). The results indicated that CeO2 improved the performance of diamond abrasive by means of strengthening the bonding between diamond grits and vitrified bond. The admirable diamond abrasive was achieved when the sample was sintered at 800°C holding for 120min.

Abstract: CBN particles coated with borosilicate glass-aluminum composite coating (Glass-Al-CBN) were prepared by a multilayer coating method. The coated composite particles were sintered at 800°C for 2h. XRD, DTA-TG, SEM techniques were used to characterize the samples. It was found that AlN was formed by the reaction of Al and CBN. The mechanical properties and the oxidation resistance of the composite was improved due to the presence of the glass coating and alumina.

Abstract: Two kinds of vitrified bonds, bond L (low temperature bond) and bond G (high strength bond), were blended by ball-milling in producing diamond wheels. Proper Sintering techniques were employed by analyzing properties of the wheel through DSC testing and fracture strength. The wheels were applied in machining PDC in comparison with similar product on market. It showed that the blended bond reached its highest fracture strength when bond L amount was about 20wt~24wt%; combination of this two kinds of vitrified bonds would improve the wheel’s comprehensive properties by raising its fracture strength to 89MPa when bond L takes up 22wt%; service life of wheels prepared by this blended bond was 30~50% longer than similar market product and efficiency improved by more than 20%.

Abstract: Nano-Cr2O3 was added to vitrified bond CBN grinding tools to improve their properties. Effects of nano-Cr2O3 on properties and microstructures of vitrified bond CBN grinding tools were investigated. The samples were characterized by differential thermal analysis (TG-DTA), scanning electron microscopy (SEM) and related detecting techniques. Results show that the refractoriness of vitrified bond firstly decreases and then increases with the addition of nano-Cr2O3, but the fluidity has the opposite change. Compared with basic vitrified bond, the refractoriness and fluidity of vitrified bond (4 wt.% nano-Cr2O3) are reduced by 25°C and increased by 5.4%, respectively. The bending strength of CBN grinding tools can be enhanced obviously with the addition of nano-Cr2O3, and it has the maximum bending strength (59.27MPa) when adding 4 wt.% nano-Cr2O3. SEM result shows that CBN grinding tool has the most dense structure and the least pore when adding 4 wt.% nano-Cr2O3.

Abstract: The purpose of this paper was to investigate the grinding performance of two types of cobalt and vitrified bond diamond tools produced by the hot press for the vertical flat grinding polycrystalline diamond. The worn diamond type and the diamond protrusion observed by the toolmaker or SEM after grinding under two different feed rates of 1 and 5 mm/min and the depth of cut of 2 µm with total depth of 10µm were studied. In addition, the grinding efficiency and the workpiece surface roughness produced were analyzed as well. The experiment results showed that when the feed rate of 1 mm/min during the flat grinding PCD was used, a lower percentage of the good diamond, a higher percentage of flat diamond and pulled-out hole on the worn surface of the cobalt bond diamond tool were obtained. For the vitrified bond diamond tool, the good diamond produced showed a higher percentage and flat grit and pulled-out hole displayed a relatively lower percentage. This may be due to the result of the relatively moderate strength and grit retention of the vitrified bond. Furthermore, the diamond protrusion and the grinding efficiency produced for the vitrified bond diamond tool were better than those for the cobalt bond tool. And the PCD surface roughness obtained was better as well.

Abstract: Grinding tests and trials on production equipment is a most expensive proposition. The expense is not only with respect to the monetary cost, but also the down time associated with interrupting a production line to make special runs and set-ups. That high cost is generally the reason given why not to conduct production grinding tests. Testing is more easily justified in a laboratory environment, however the testing can become “clinical” such that it is far removed from the real world of production grinding and the results are often unrealistic. It has been the object of this project to target an industry and simulate, as closely as possible, a production grinding environment, in the laboratory, to encompass all of the realism of bearing production but with quick-changeover features that allow frequent and accurate adjustments to the process with respect to the set-up but moreover, the grinding fluid. The end result is test data that is meaningful, directly relevant, acceptable and understandable to the industry. It has also provided a platform for further investigative work with respect to the surface texture produced by certain fluid chemistries.

Abstract: The use of cubic boron nitride (CBN) over conventional abrasives in ferrous and superalloy grinding has resulted in improved manufacturing throughput and beneficial mechanical properties on workpiece surfaces. However, through the innovative use of crystal synthesis techniques, the grinding performance can be further improved over existing CBN crystals. In this study, such a new CBN crystal is developed, characterized, and its grinding performance is compared to a commercially available CBN crystal. Grinding tests are conducted in AISI M2 steel and Inconel-718 superalloy using a vitrified bond configuration with applicability in a wide range of end-use applications.