Papers by Keyword: PCBN

Abstract: Polycrystalline cubic boron nitride (PcBN) composites were fabricated by spark plasma sintering (SPS). The SiC, Si₃N₄ and Si/B were used as binder. The effects of SPS sintering process parameters, such as the sintering temperature, holding time, heating rate and binder composition, on the properties of PcBN samples were investigated. PcBN composite with a hardness of 23.12GPa was fabricated efficiently by SPS. The hardness of PcBN sample increased first and then decreased with the increase of sintering temperature. As the holding time was 20 min, the hardness of PcBN sample was the highest. The PcBN performance at the heating rate of 50 °C/min was significantly better than that of 100°C /min. When the binder component of SiC, Si₃N_4, and Si was 63%:27%:10%, the hardness of PcBN was the highest. With an addition of Si, the PcBN samples had higher hardness than that of B.

Abstract: Polycrystalline cubic boron nitride (PcBN) composites were sintered by high pressure and high temperature sintering (HPHT) at 1450 °C for 3 min under a pressure of 5.0 GPa. Aluminium,boron carbide and carbon in the starting mixture reacts with cubic boron nitride (cBN) to form Al₃BC₃ and AlN bonding among cBN grains during sintering. X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to analyze phases and micro-structure of the sintered samples. The dense structure of super hard cBN grains bonded together with Al₃BC₃ and AlN offers superior hardness and high strength. The Vickers hardness of PcBN composites was 45±5 GPa, and the strength of PcBN composites was 345±15 MPa.

Abstract: SiC-Al₃BC₃-cBN composites with different contents of cBN were fabricated by high pressure and high temperature sintering (HPHT) at 1450 °C for 3 min under a pressure of 5.0 GPa using SiC, Al, B₄C and C as additives. The effect of SiC content on the density and mechanical properties of SiC-Al₃BC₃-cBN composites was investigated. X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to analyze phases and micro-structure of the sintered samples. The hardness of SiC-Al₃BC₃-cBN composites decreased with the increasing of SiC content, However, the fracture strength of SiC-Al₃BC₃-cBN composites increased with the increasing of SiC content.

Abstract: PCBN-inserts have a high potential in the cutting of hardened steel, cast iron and super alloys due to their high hardness and heat resistance. Nevertheless they have a high purchase price, which lowers the economic benefits for the end user compared to other cutting materials. This is caused by the high production costs of the inserts. The grinding of PCBN-inserts causes a major proportion of these costs as a result of the high grinding wheel wear. The primary wear mechanism is grain breakout followed by clogging of the grinding layer. This study shows that the efficiency of the grinding process can be increased significantly by applying low cutting speeds and high feed rates. In this case, splintering of the grinding grain is the main wear mechanism.

Abstract: Abstract: Corner radius as a non-main cutting parameters, study of corner radius about cutting vibration is relatively small.Turning experiments use PCBN tool in CAK4085 CNC lathe,cutting hardened steel HRC50-52 Cr12MoV and hardened steel HRC62-64 GCr15, eddy current sensor measure the tool vibration amplitude of each group parameters, analysis influence of the corner radius for tool vibration amplitude. With corner radius increases, tool vibration amplitude increases. Research will contribute to the development of high-speed machining of hardened steel.

Abstract: Precision grinding is one of the important processes for finishing of hardened steel parts. However, the grinding process might be quite costly providing the parts with shape complexity should be finished because a number of production steps are needed. Also, this process has some environmental issues, such as disposal of a large amount of grinding sludge and grinding fluid. Precision cutting would become a better alternative process to reduce cost and environmental burden because process steps can be simplified by use of CNC machine tools with PcBN cutting insert if deterioration of cutting tool edge by wear and chipping can be suppressed for long duration. In this study, to improve performance of a PcBN cutting insert, such as wear resistance and defect resistance by the applying of pulse laser processing to sharpen cutting edge in order to realize substitution of cutting for grinding. Precision cutting experiments for hardened steel are conducted by use of the PcBN insert with sharp and tough edges processed by pulsed laser and, for comparison, by use of the PcBN insert ground with diamond wheel. From the results of cutting experiments, it was found that precision cutting with PcBN insert processed by pulsed laser can provide a steady cutting state for a long cutting duration, and a smooth finished surface comparable to precision grindings.

Abstract: The paper presents the influence of various cutting regimes on the surface roughness, when a hardened bearing steel has been machined using both ceramic and PCBN cutting tools. There were used different cutting conditions varying cutting speed, feed rate and depth of cut in order to determine the influence of each cutting parameter on the surface finish.

Abstract: The high temperature strength of Ni-based superalloys coupled with excellent corrosion resistance make them ideal for aerospace applications. However, the difficulty in finish machining superalloys with the carbide tools presents the short tool-life. Polycrystalline Cubic Boron Nitride (PCBN) is potential to machine superalloys. To data, there are many researches about PCBN tool wear, but only little papers showing how the surface roughness and the wear speed are influenced by cutting parameter and the coolant during the differences periods of PCBN tool wear. This investigation has been conducted to show that the PCBN tool wear is slower with cooling that without cooling during cutting superalloys with PCBN tool especially in VB up to a certain value. It is shown that tool fracture can be reduced by using the cooling. In the process of PCBN tool wear, in addition, there are some differences of the effect of the cooling for roughness Ra values.

Abstract: In order to increase tool life and workpiece surface quality, cutting processes with geometrically defined cutting edges demand inserts with a targeted prepared edge. For example, chamfers are largely used in many processes to provide edge strengthening without damaging the chip flow. In order to achieve a stable and reliable cutting process, small and uniform chamfers are necessary. In this context, the influence of grinding parameters on the edge quality and on the chamfer width deviations is investigated. It was found that larger abrasive grains increase edge chipping and that elastic deformation during chamfer grinding at insert corner radius is the main responsible for chamfer width deviation.

Abstract: PCBN cutting tool is widely used in turning process and known as second best cutting tool after Diamond. This study investigates the suitability of PCBN cutting tool to cut variety types of steel. Experimental results for three major parameters which are cutting speed 150, 175 and 200 m/min, depth of cut 0.1, 0.2 and 0.3 mm, and feed 0.1, 0.2, and 0.3 mm/rev were converted into surface roughness analysis to look on the performance of PCBN to cut three different types of steels. The selected work materials of carbon steel AISI 1040, alloy steel AISI 4140 and tool steed AISI D2 were machined in dry tuning process with constant cutting length 50 mm and initial workpiece diameter 40 mm. At the end of this study, it is shown that higher cutting speed produced better surface roughness for AISI 1040 and AISI D2 but worsen the surface of AISI 4140. Low feed value is the most practical parameter to be used to produce fine surface finish using PCBN cutting tool. Fluctuate roughness value produced by increasing depth of cut use in turning parameters and no specific relationship can be concluded between depth of cut and surface roughness value.