Advanced Materials Research Vol. 1017

Abstract: Cutting technology is one of the important methods to fabricate small-sized precision components in the semiconductor, electro-mechanics, and automobile industries. This paper focuses on high efficiency machining of small hole drilling for PPS (Polyphenylene Sulfide). In this paper, drilling experiments were designed to investigate the influence of the depth of cut on the burr formation. The experimental results obtained are as follows, (1) The thrust force and radial force increase with the increase in feed per revolution and depth-of-cut. (2) On the prevention of burr formation, the step feed is better than the non-step feed. Also, the burr formation decreases with the increase in the feed per revolution. (3) The hole straightness increases with the increase in depth-of-cut.

Abstract: Pull broaching fir-tree slots of gas turbine is one of the most productive precision machining processes when machining simple surfaces or complex contours. Tool edge chipping and wear of uncoated broaching tool become a serious problem in the currently broaching of gas turbine discs. Therefore, tool coating can be used to improve the wear resistance of broaching tool. AlCrN-based coatings have been developed as a high hardness coating for cutters due to excellent resistance to oxidation which is higher than that of conventional coatings. However, few researches had paid attention to investigating AlCrN-based coating tool performance in the broaching process, especially in machining of heat-resisting material of heavy-duty gas turbine discs. In this paper, experiments of broaching heat-resisting material X12CrMoWVNbN1011 were investigated. In order to obtain suitable and ideal broaching tool, the AlCrN coated or uncoated T15 broaching tools were also compared. Cutting force, cutting temperature, and tool wear were measured in the broaching experiments. Results showed that: (1) with a little changed cutting load and tool edge radius, AlCrN-based coating was found to have more significantly influence in improving the tool life as comparing to uncoated tool. The similar wear forms was observed by comparing coated tool and uncoated tool. The conclusions of the study can help to improve heavy-duty gas turbine disc broaching process and broaching tool. (2) Owing to AlCrN coating’s unique combination of heat resistance and hardness, broaching tool could reach higher cutting performance levels. AlCrN coated tool compared with uncoated tool have much better performance in term of cutting strains or cutting temperature.

Abstract: This paper describes an influence of the cutting atmosphere and the carbon content on the surface roughness and tool wear in CO₂-blow cutting of carbon steel with a diamond tool. The cutting tests were carried out by changing the cutting atmosphere and carbon contains in order to investigate the effect on the improvement of surface finish and the reduction of tool wear. The results indicated that the roughness on finished surface was improved by cutting in CO₂ gas blow atmosphere and the tool wear increased with a decrease in the carbon content.

Abstract: Ultrasonic cutting is a technique that can improve machinability such as fine surface, reduce tool worn out and etc. To improve processing speed of ultrasonic cutting is difficult due to the effects of tool oscillation are invalidated when cutting speed exceeds maximum tool oscillating velocity. In previous report, high speed principal direction ultrasonic turning without thrust direction vibration experiments for stainless steel were carried out to improve processing speed and products quality. In ultrasonic turning, tool worn out and built up edge generation were reduced compare with ordinary turning. Fine surface without thrust direction periodically cut marks were obtained in ultrasonic turning experiments. In this study, the effects of chip breaker shape and insert material were investigated. Surface roughness, chip worn out and built up edge generation were investigated in this study.

Abstract: This paper describes the effect of oil-immersion treatment on the surfaces of cutting tools. In this study, the ‘oil-immersion treatment’ refers to the modification of the tool’s surface by immersing the tool in a treatment solution and heating under pressure. Our previous study demonstrated that such treatment reduces the wear on cutting tools. In this study, the effect of oil-immersion treatment on a carbide cutting tool was investigated by EPMA (electron probe microanalysis) and XPS (x-ray photoelectron spectroscopy). SEM (scanning electron microscope) and EPMA examination revealed that oil-immersion treatment reduces the amount of cobalt on the tool’s surface and forms sulphur deposits. XPS analysis of the chemical bonds on the surfaces revealed the presence of cobalt sulphide and inorganic carbon. In addition, friction tests showed that the oil-immersion treatment reduces the friction coefficient of the tool.

Abstract: Carbon Fiber Reinforced Plastic (CFRP) is a high-strength and high-elastic-modulus composite material that is hardened by impregning carbon fiber with epoxy resin. Although, many sutdies of hole drilling of CFRP have been conducted, few sutdies of face milling of CFRP have been carried out. Face milling is necessary for surfaceing of aerospace parts, which is indispensable for airplane construction. Machining of CFRP is difficult because of the extreme tool wear and delamination that occur. The authors investigated face milling of CFRP using a newly developed Poly Crystalline Diamond (PCD) tool. The resultts show, that the cutting force and surface roughness are affected by the fiber orientation of the CFRP, and that delamination can easily occur in the outer layer of face-nilled CFRP.

Abstract: Binder-less nanopolycrystalline cBN (BL-PcBN) synthesized by direct conversion under high pressure and high temperature has a fine texture consisting of small cBN grains (<100nm), high hardness (40–50 GPa) and high transverse rupture strength (1.3–1.6 GPa). Their mechanical properties strongly depend on their starting materials and synthetic conditions. In this study, Ball-end mill tools prepared from several kinds of BL-PcBN synthesized under various conditions (8–20 GPa, 1500–2300oC) were examined for precision cutting of high-strength hardened steel comparing with conventional sintered cBN. A fine mirror-finish surface with Ra of 20 nm could be produced by precision BL-PcBN tools, while not by conventional sintered cBN tools. The tool wear of BL-PcBN synthesized from hBN at 10 GPa and 2200°C was four to five times less than that of conventional cBN. These results revealed that the BL-PcBN tools have excellent potential for precision cutting on ferrous materials.

Abstract: The core idea of the existing cooling methods in grinding process is making a large quantity of coolant into the contact zone. However, the practical quantity of coolant injected in the grinding zone is limited, and the large amount of coolant employed can cause pernicious effect to human health and the environment, and will largely increase the expenses. In order to solve this problem, an environmental friendly idea about enhancing heat transfer in the contact zone based on heat pipe technology is put forward in this paper. The new system, heat pipe grinding wheel (HPGW), based on this high-efficiency cooling technology is developed and its heat transfer principle is illustrated. Eventually grinding experiments with HPGW were carried out to verify the cooling effect by comparing with non-HPGW in grinding plain carbon steel. Results show that using HPGW can significantly reduce the grinding temperature with no coolant.

Abstract: Nickel-based alloy is known as one of the most difficult–to-machine materials and the milling process is one of the most common metal removal operations. Modeling and simulation of milling process have the potential for understanding the milling mechanism, improving cutting tool designs and selecting optimum conditions, especially in advanced applications such as high-speed milling. This paper presents a 3D coupled thermo-mechanical finite element model based on ABAQUS\Explicit for the simulation of Inconel 718 chip formation in metal cutting. In the simulations, a Lagrangian formulation with an explicit solution scheme and a penalty contact algorithm has been used. The material behavior is modeled with classical Johnson-cook plasticity constitutive model and dynamic failure criteria for element removal, coupled with adaptive meshing and mass scaling technology for limiting the calculation time. The milling tool is modeled in UG software according to the real tool geometry, and meshed as a rigid tool. In order to verify the accuracy of 3D simulation, results (cutting forces and cutting temperature) were compared with the experimental results under the same cutting conditions as the simulations. The results obtained indicate that the simulation methodology is capable of predicting the cutting forces and cutting temperature. It suggests that 3D finite element simulation model of cutting processes can be truly trusted.

Abstract: Wear characteristics of binder-less (single-phase) nanopolycrystalline diamond (NPD) and cubic boron nitride (BL-PcBN) were investigated by rubbing them against various ceramics such as SiO₂, Si₃N₄, Al₂O₃ and SiC. The wear rates of NPD and BL-PcBN against SiO₂ and Si₃N₄ at high speed rubbing (280-360 m/min) at a loading pressure of 55 MPa (starting condition) were considerably high, indicating the main wear process is a chemical reaction. BL-PcBN specimens were found to be worn at much higher (more than ten times) rates than NPD, suggesting that cBN highly reacts with these ceramics in comparison with diamond under the experiment condition.