Advanced Materials Research Vol. 497

Abstract: Traditionally, single point diamond turning (SPDT) can not process ferreous metals because of acute tool wear. Ultrasonic vibration-assisted cutting(UVC) provides a promising solution for the problem. In this paper, for the aim of directly obtaining mirror surface on die steels, UVC method was used combining with SPDT process. Experiments were carried out on an ultra precision turning machine, cutting parameters and vibration parameters were well-chosen, and two kind of feed rates, two kinds of prevailing die steels were experimented. Mirror surfaces were successfully achieved on face turning, with the best roughness of Ra16.6nm. And the surface roughness, surface texture and tool wear in machining process were discussed.

Abstract: In traditional manufacture of grinding wheel, a key problem is the randomly arrangement of the diamond abrasives, which results in randomly distribution of surface roughness. In this paper, through controlling the magnetic field during the forming process of the grinding wheel, arrangement of diamond abrasives is orderly to obtain a more orderly surface roughness. The forming process of diamond fine grinding wheel is studied under magnetic field controlling. The grinding experiment for aspherical mold was carried out on the tungsten carbide YG8 and the surface quality after grinding was also analyzed

Abstract: Cup wheel grinding and etching pretreatment are widely used in complex coated cemented carbide cutting tools machining process. The two processes determine different surface properties due to various mechanical and thermal loads in grinding and complex chemical reaction in etching pretreatment. In this paper, the effect of the grinding wheel speed, the grinding feed rate and the etching time with the Murakami and acid solution on the residual stress and surface topography of coated cemented carbide cutting tools are investigated. After each process, the samples are characterized by scanning electron microscopy and X-ray diffraction. It is found that the grinding wheel speed has a significant influence on residual stress measured in the WC phase. Etching by Murakami generated smooth surface, which partly removed the near-surface residual stress quickly but cannot eliminate.

Abstract: Demands of glass Fresnel lens is increasing in solar panel in order to increase power efficiency. Glass lens is usually molded by glass molding method with tungsten carbide molds. In this study, large Fresnel lens molds made of tungsten carbide are tested to be ground by simultaneous 2-axis (Y, Z) controlled grinding method. The resinoid bonded diamond wheel was trued with a rare metal truer to improve the sharpness of the wheel edge. In the grinding test of the tungsten carbide mold, a form accuracy of less than 0.8 μm P-V and surface roughness of 18 nm Rz were obtained, and it is clarified that the proposed grinding method is useful for the Fresnel grinding.

Abstract: In the process of grinding precision balls, the motion state of balls has an important influence on the efficiency and quality. However, the normal movement of balls will be damaged because of slipping, so it must be avoided. Besides, to process different materials of balls, it should use different processing parameters. This paper studies a numerical analysis on the kinematic characteristics of the motion of balls, analyzes processing parameters which impact the motion of balls during grinding and the difference of the motion state of bearing balls and resin balls. Study shows grinding pressure and plate speed have a great influence to the motion of balls during grinding.

Abstract: In the present study, sawing forces of Al2O3 ceramic and wear of metal-bonded diamond cut-off wheel were examined by counting the statistical data of diamond wear and analyzing the force signals under different sawing conditions. The experimental results demonstrated that normal grinding force reduced with the increasing of sawing speed, and rose with the increasing of workpiece feed rate and grinding depth. In all of the variables, sawing depth made the greatest effects on normal grinding froce. The percentage of whole crystal or pull-out crystal decreased and fractured crystal increased as the sawing depth increased or the sawing speed decreased. Among machining factors, sawing speed was the greatest effectors on the wear of diamond cut-off wheel.

Abstract: The TiAlN and AlTiN coated carbide cutting tools were adopted for high-speed turning of α+β phase titanium alloy Ti-6Al-4V. Both the wear pattern and wear mechanism were investigated in this research. Results show that: MQL condition can greatly prolong the tool life of AlTiN coated carbide tool but has minor influence on improving the tool life of TiAlN carbide tool. AlTiN coated carbide tool was found to be qualified to obtain better cutting performance and longer tool life and is more suitable for processing titanium alloy TC4 compared with TiAlN coated tool under the same cutting parameters. In dry cutting condition, both adhesive and oxidation wear were observed to be the main wear types in these two coated carbide tools. However, in MQL condition, TiAlN coated tool may only suffer adhesive wear while the AlTiN coated carbide tool suffer adhesive, diffusion and oxidation wear.

Abstract: Three kinds of whisker toughened composite ceramic tools were prepared by carbothermal reduction process and their fracture performance was investigated in cutting the quenched 45 steel. The results suggest that the ratio of C to N has an effect on the fracture resistance of ceramic tool, and the whisker in tool material can inhibit the crack propagation and desquamation of grains. At the low cutting speed, the main fracture mode was conchoidal desquamation on the tool rake face and severe oxidation wear and some diffusion wear happened. At the medium cutting speed or high cutting speed, a combination of mechanical load and thermal load applied on the tool and adhesion was caused between workpiece material and tool material, and so the fracture mode was break-off of the cutting edge.

Abstract: The performances of different coated carbide drills when drilling cast GH625 nickel-based alloy were evaluated in terms of tool wear and cutting force. Wear pattern observation and cutting force measurement were conducted under different cutting conditions. It was found that the drill coated with TiAlN/TiN showed the best overall performance among all the drill types tested. This drill type gave the longest tool life in terms of number of holes partly due to the excellent wear resistance of TiAlN/TiN multilayer. Besides, the thrust force and torque produced with this drill type were lower, which could be attributed to its good adhesion resistance and chip-ejection ability.