Papers by Keyword: Cubic Boron Nitride (CBN)

Abstract: The efficiency of using of CBN grinding wheels highly depends on the dressing process as well as on the coolant lubricant used. The Institute of Grinding and Precision Technology (KSF) investigated the performance of vitrified CBN grinding wheels -being dressed using different parameters- while using two different grinding oils and two different water-miscible coolant lubricants. The obtained results show that the performance of the vitrified CBN grinding wheels regarding the quality of the workpiece surface, the grinding forces as well as the wear of the grinding wheel, highly depend on the dressing conditions and the type of the coolant lubricant used. Compared to the water-miscible coolant lubricants, the grinding oils show better results.

Abstract: In many grinding applications, the material removal rate (MRR) is constrained by undesired thermal surface damages like burns and tensile residual stresses as well as dimensional inaccuracy. In dry grinding, due to lack of coolant, the limitation to achieve higher MRR is more critical as the major part of the heat, generated on the contact zone, is transferred to the workpiece. That is why the lower heat generation is a most important target by dry grinding. This paper presents some of the very interesting results by a comparison between a structured electroplated CBN wheel and a conventional one during surface grinding of steel. One of the grinding wheels has the normal structure and the other has special macro-structure topography developed for dry grinding. The results show a considerable reduction in grinding forces and less thermal damages using the novel electroplated CBN wheel comparing to conventional wheel.

Abstract: In this study, turning of the cemented carbides that their WC particle size was standardized were carried out with the PCD and the cBN tools. The WC particle diameter of cemented carbides was about 2µm and the Co contents were 10, 15, 20 and 25%, respectively. The influence of the WC particle size and Co contents was investigated. Summary of results are shown as follows: (1) In turning with the PCD tool, the more the Co contents increase, the more the tool wear increases. (2) In turning with the cBN tools, the more the Co contents of the work material increase, the more the tool wear decreases. (3) In turning of the cemented carbides contained the larger quantity of Co, the cBN tools are more effective than the PCD tool.

Abstract: SiAlON-cubic boron nitride (cBN) composite was prepared by spark plasma sintering (SPS) using -SiAlON and cBN powders as starting materials, and the effect of holding time on densification, phase transformation and hardness of the composite was investigated. The SiAlON-cBN composite containing 20 vol% cBN sintered at 1650oC for 60s was densified to >97% of theoretical density. cBN phase transformed to hexagonal boron nitride (hBN) in the SiAlON-cBN composite with increasing holding time at 1650oC. Vickers hardness of the SiAlON-20vol%cBN composite sintered at 1650oC for 60-300s was 17.7GPa, and the hardness decreased with increasing holding time.

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.

Abstract: Ultrasonic vibration cutting experiments have been carried out for the machining of the plasma-sprayed Al2O3 coatings. The optimized value of V/Vc for the vibration cutting was obtained by a series of tests. The comparing experiments of the ultrasonic vibration cutting and the traditional cutting for the machining of the plasma-sprayed Al2O3 coatings by the cube nitride boride (CBN) and YC09 (hard alloy) lathe tools have been executed. The results indicate that the valid cutting time for the vibration cutting is 3-4 times longer than that for the traditional cutting, at the same time, the surface roughness values of the coatings machined by the vibration cutting are less than that machined by the traditional cutting. CBN and YC09 have been optimized as the candidates to machine the Al2O3 coatings through a series of vibration cutting tests carried out on the lathe tools of CBN and three hard alloys of YC09, YH3 and YGHT. The cutting parameters, such as V, aP and f, for the vibration cutting of the Al2O3 coatings by CBN and YC09 were obtained through the orthogonal tests and regression analysis. The obtained parameters have been utilized to machine the plasma-sprayed Al2O3 coatings for validation, and the results indicate that the ultrasonic vibration cutting is a competitive method to machine the plasma-sprayed Al2O3 coatings.

Abstract: In this paper microcrystalline CBN abrasives are prepared with CBN powders and vitrified bond additives by pressureless sintering method. Mechanical properties of the products are measured by using single particle compressive strength tester and three-point bending strength tester. The effects of vitrified bond additives, the CBN powders particle size and the sintering temperature on the performance of microcrystalline CBN abrasives are investigated. The microstructure characteristics of microcrystalline CBN abrasives are examined. The results showed that the performance and microstructure of microcrystalline CBN abrasives are significantly influenced by particle size of CBN powder and the addition amount of vitrified bond.

Abstract: Ultrasonic-vibration-based hardened-gear honing is creativity technique in the domain of gear finishing. The honing technique is improved by introducing ultrasonic machining to improve the accuracy and surface quality of hardened-gear. With respect to the design and manufacture of ultrasonic-vibration-based gear honing machine, the paper refers to reasonable project and trial-manufacture. The electroforming technique of spur gear CBN honing-wheel is helpful to improve the comprehensive performance of honing-wheel. Finally the characteristic and advantage of ultrasonic vibration based gear-honing technique is described.

Abstract: The present study was undertaken to compare the consumed power in surface grinding of three different materials with a vitrified CBN wheel. High speed steel, stainless steel, and natural granite were used as the workpiece materials in the experiments. Two different depth of cut and workpiece velocity were combined to give different material removal rates. The spindle power was in-process monitored in each pass of grinding. The radius wear of the grinding wheel was also measured and the morphologies of CBN grains were observed during the grinding of high speed steel and granite. The power for the grinding of high speed steel was found to be the lowest under any operating parameters. For other two materials, the results became complex. At shallower depth of cut, the power for the grinding of stainless steel was higher in most cases. However, the power for the grinding of granite was higher under larger depth of cut. It was found that the grinding wheel failed much earlier in the grinding of granite as compared with the grinding of high speed steel.

Abstract: βSiAlON-cubic boron nitride (cBN) composites were prepared from β-SiAlON and cBN powders using spark plasma sintering (SPS) at firing temperature of 1600-1900oC under pressure of 100MPa, and densification, phase transformation and hardness of the composites were investigated. The phase transformation of cBN to hexagonal BN (hBN) was inhibited in βSiAlON-cBN composite. βSiAlON-cBN composites containing 10-30 vol% cBN fired at 1650oC were densified to 95-98% of theoretical density with no transformation of cBN to hBN. Vickers hardness of the βSiAlON-cBN composite containing 20 vol% cBN fired at 1650oC was 17.5 GPa in maximum value, and the hardness significantly decreased as cBN phase was transformed to hBN in the composites.