Key Engineering Materials Vols. 375-376

Abstract: Two kinds of specimen made of a kind of Ta-W alloy material with high melting point about 3000°C were processed by a traditional EDM (TEDM) and a powder mixed EDM (PMEDM) separately, and its surface characteristics were tested. After processing, their surfaces had the roughness of Ra 0.542μm and Ra 0.174μm, respectively. Moreover, their surface wear-resistance was studied on a CJS111A friction and wear tester. The micro-appearances on the wear surfaces were observed and analyzed by using a SEM. The test results indicated that the better wear-resisting ability the specimen, the higher wear rate displayed during the test the grinding balls. The wear rates of grinding balls corresponding to the two processed surfaces are 2.4×10-5 mm3/m for the TEDM and 1.4×10-4 mm3/m for the PMEDM, and the latter is 5.8 times of the former. The results show that the PMEDM is better at improving the wear-resistance, roughness and hardness than the TEDM, which means that the technique of PMEDM has a great potential in processing the special material.

Abstract: In this paper, the measurements of microhardness and tensile properties are performed to the electroformed Ni-Mn alloys which the mean grain size is near to or less than 100nm. It is studied that the effect of average deposition current density on microhardness and tensile properties of the alloys and the effect of post-electroforming annealing on microhardness of the alloys. The results show that with the increment of average current density, microhardness and strength of the alloys increase and elongation decreases because of the increment of Mn content and the decrement of grain size of the alloys. Microhardness of the alloys are slightly improved after annealing.

Abstract: Based on analysis of the mechanism of Electrical Discharge Machining (EDM) and the characteristics of deposition processing, the processing conditions of micro EDM Deposition (micro EDD) are determined. Micro EDD is a new EDM method taking air as machining medium, using narrow pulse width, long pulse interval, low discharge current and connecting the tool electrode with the anode of pulse generator. Using EDM shaping machine and brass, tungsten and steel as tool electrode respectively, micro cylinders are deposited on high-speed steel surface. And then the microstructure of deposit is analyzed detailedly. Results show that elements of the deposited material distribute uniformly, whose components depend on the tool electrode material. As the high cooling rate of the solidification process, the deposit grain size refines obviously, which leads to the hardness of tungsten or steel deposit increasing. Moreover, the Metallurgical bonding has occurred on the interface between deposit and high-speed steel base, whose thickness is about 5μm.

Abstract: Green Manufacturing is a sustainable development model in modern manufacturing. From the perspective of green manufacturing, the environmental impacts of cutting fluid in cutting process was analyzed, the design strategy without cutting fluid in green cutting technology was studied, and some measures on machine tool design and the thermal deformation reduction of workpiece and machine were presented.

Abstract: In this paper, the development and mechanical, physical properties on cermet cutting tool material are described. By using the cermet insert NT7 developed in recent years and WC based carbide insert YT14, the tool wear, impact and cutting force tests to high strength steel 38CrNi3MoVA (hardened and tempered, HRC36~40) are processed respectively. The results of these tests demonstrate that NT7 cutting tools have better performance on some characteristics, such as wear resistance, tool life and cutting force. And its ability of impact resistance is similar to YT14. These researches will benefit to the poplarizaion and application of cermet cutting tool.

Abstract: This article illustrates the production method and mechanical & physical properties of polycrystal cubic boron nitride (PCBN) cutting tool material. As shown by the turning machining of hardened steel, cold-hardened cast iron and composite materials, PCBN cutting tool is superior in cutting performance to cemented carbide and ceramics cutting tools. In recent years, with great improvement in production process and overall mechanical properties of PCBN cutting tool material, it can effectively make rough machining of ferrous metal. This article contributes to the popularization and application of this cutting tool.

Abstract: Green cutting is ecologically desirable and have been a tendency in the industry field. Water vapor can be introduced in metal cutting as coolant and lubricant due to its pollution-free, generating easily and unneeded disposal. Therefore, water vapor is an environment-friendly coolant and lubricant in machining. This study attempts to understand the effect of water vapor as coolant and lubricant on chip formation. In the comparison experiments to dry and wet cutting, water vapor jet flow from a developed generator is applied into cutting zone directly. When YG8 (K20 in ISO) tools are used to turn titanium alloy TC4 (Ti-6Al-4V), Ni-based super alloy GH3030 and stainless steel 1Cr18Ni9Ti in orthogonal cutting, through quick-stop tests, the photos of polished chip sections microstructure were obtained. And the results suggest that the application of water vapor produces the least BUE, tool-chip contact length but the largest deformation coefficient and shear angle. The water vapor as coolant and lubricant could be a substitution of cutting fluid to carry out green cutting in the machining of difficult-to-cut materials.

Abstract: For the cutting of the difficult-to-machine materials, such as stainless steel and dead-hard steel, is always puzzling and restricting manufacturing, it is necessary to deeply study and search after new machining methods in respect of both theory and practice. This paper chose waved-edge milling inserts and flat-groove milling inserts of different materials to make cutting force contrast experiments on stainless steel ZG0Cr13Ni5Mo, chose ultrafine-grain inserts, YT14 inserts (local product) and CY250 inserts(foreign product) to make cutting life contrast experiments on dead-hard steel ZG35CrMo, then researched in theory the disrepair appearance, the BSE image and the granularity. The research results show that the integrated cutting capability of ultrafine grain waved-edge milling insert is excellent for difficult-to-machine materials.

Abstract: Johnson-Cook (JC) constitutive model is extensively used in the simulation of metal machining. There are several different sets of JC material constants for titanium alloy Ti6Al4V fitted by split-Hopkinson bar (SHPB) tests. However, few researches have been done to study their sensitivity on the behavior of cutting. In this work, four different sets of material constants were performed in a 2D numerical model to simulate the cutting process of titanium alloy Ti6Al4V. The effects of the four sets of material constants on the predicted cutting forces, chip morphology and temperature were studied. It is shown that all the considered process outputs are very sensitive to material constitutive constants. Some quantitive comparisons with experimental results reported in the literature were also made.

Abstract: By cutting experiments, this paper investigates the effect of various chamfer widths and chamfer angles on cutting force, cutting temperature, and chip morphology when hardened steel GCr15(HRC60+2) is machined with PCBN tools. The research results indicate that with the enlargement of chamfer angle both cutting temperature and main cutting force increase gradually, and especially, radial force increases more significantly. In addition, it is shown that as chamfer width increases both cutting force and cutting temperature rise. The analytical results of chips derived from cutting experiments reveal that chamfer angle being 20º, chips are the thickest and less serrated. Furthermore, chip thickness diminishes gradually with the increment of chamfer width.