Advanced Materials Research Vol. 1136

Abstract: The use of hard and brittle materials for manufacturing optical parts, such as dies and molds are required in order to extend mold life. Although, cobalt-free tungsten carbide is one of the hardest materials, micro-cutting is very difficult due to its hardness and its brittleness. This paper investigates face turning of cobalt-free tungsten carbide using a nanopolycrystalline diamond [NPD] tool and Zinc dialkyldithiophosphate (ZnDTP) fluid. Surface roughness of the cobalt-free tungsten carbide achieved was 22nmRz, which is far larger than the theoretical value. That is, traditional cutting theory does not directly apply for face turning of cobalt-free tungsten carbide using NPD tool and ZnDTP fluid.

Abstract: A titanium alloy and stainless steel is an excellent material having properties such as high intensity and high corrosion resistance. Therefore, a titanium alloy and a stainless steel are used as material of steam turbine blade. However, the machining efficiency of a titanium alloy and a stainless steel is a low because of difficult-to-cut materials. Especially, it is a major problem that the cutting point temperature is high and the tool life is short. In the conventional study, it is reported that the cutting point temperature is low and the tool life becomes long by cutting at the suitable cutting speed corresponding to material characteristics. This concept is known as high speed milling. In recent years, the high speed milling is actually used for the metal mold machining. In this study, the high speed milling of the titanium alloy and the stainless steel was tried for the purpose of high efficiency cutting of a steam turbine blade. In the experiment, the cutting tool used the TiAlN coating radius solid end mill made of micro grain cemented carbide. The diameter of endmill is 5mm. The corner radius is 0.2mm. And, the work piece is the titanium alloy Ti-6Al-4V and stainless steel 13Cr. The cutting speed carried out at 100m/min~600m/min. As the result, when the tool life and the surface roughness was a valuation basis, the optimum cutting speed of titanium alloy was 300m/min. On the other hand, In the case of the stainless steel, the flank wear becomes large in proportion to cutting speed. The feature of high speed milling was not able to be confirmed in the range of this experimental condition.

Abstract: AlMgB₁₄ is a novel hard and brittle material which need be improved toughness for utilizing as cutting tool materials. In present study, intermetallic compound Ni₃Al were attempted to dope the synthesised AlMgB₁₄ materials. The microstructure of the AlMgB₁₄-Ni₃Al composites was analysized by scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) and an X-ray diffractometer (XRD). The density, hardness and fracture toughness of AlMgB₁₄-Ni₃Al composites were also measured. The results showed that the major phases in AlMgB₁₄-Ni₃Al composites were AlMgB₁₄, MgAl₂O₄ , Ni₃Al and NiAl as well as W₂B₅. With the increasing of the amount of Ni₃Al, more transgranular fractured features can be found in the fractured surface, the density of the AlMgB₁₄-Ni₃Al composites was increased, the hardness and fracture toughness of the AlMgB₁₄-Ni₃Al composites were decreased.

Abstract: The chip formation mechanism during precision cutting of metallic glass (Zr₅₅Cu₃₀Ni₅Al₁₀ at%) was investigated around the glass transition temperature (673 K). Orthogonal cutting of metallic glass are conducted on a fly-cutting machine at various cutting speeds. The new surface of the chips was slightly shiny while the free surface exhibited lamellar slip structure. The cutting temperature was a proportional to the cutting ratio and chip shear angle. The surface integrity worsened with an increased flow of cutting chip due to an increase in the cutting speed. An increase in the cutting temperature caused the chips formation to change from flow type chips to discontinuous chips. When the cutting speed exceeded 300 m/min, the shear angle increased while the shear pitch of the chips decreased. It appears that when the cutting temperature exceeded the glass transition temperature, the strength of the metallic glass decreased and the ductility mode changed due to viscous flow.

Abstract: Potassium Dihydrogen Phosphate (KDP) crystal is widely used in laser frequency multiplications and electro-optical modulators, but its soft-brittle property and thermal sensitive characteristic make it a very difficult-to-machine material. In this paper, an in-house made diamond tool with one tooth is used to face-mill KDP crystal specimens on a high-speed micro CNC machining centre, based on a statistically designed experiment. The morphology and roughness of the milled KDP crystal surfaces are analyzed with respect to the process parameters. It has been found that cutting speed has the largest effect on surface roughness, while axial depth of cut and feed per tooth show a comparable effect on both the Ra and PV roughness measures. From this study, 3 m/s cutting speed, 3 μm axial depth of cut and 1 μm/z feed per tooth are recommended for single point diamond milling of KDP crystal.

Abstract: A diamond tip with included angle of 90° and fillet radius of 45 nm is developed combining precision grinding and focused ion beam. Relatively high speed scratching at 8.4 m/s induced by the developed diamond tip is conducted on silicon (Si) (111) plane using an ultraprecision grinder. Width at the onset of chip formation on a Si wafer is 193 nm. Width and depth at the onset of crack formation are 1125 and 94 nm, respectively. Calculated normal forces at the onset of chip and crack formations are 424 μN and 14 mN, respectively, corresponding to the depth of cut is 44 and 466 nm.

Abstract: Ductile removal behavior of hard and brittle material in the process of machining has always been a sticking topic. A series of nanoscratch tests of K9 glass were conducted with Berkovich probe on nanoindenter XP to investigate the ductile removal process, material deformation and crack damage. It was found that the scratches surface was free from crack damage in the range of the selected scratching parameters and excellent machinability of K9 glass was obtained. The observation also showed that the stable chips were distributed on the sides of the scratches and the deformation of chips was much larger than that obtained in the conventional machining. Meanwhile, a pile-up phenomenon was obvious and the residual depth of scratches was decreased with the increasing of scratch velocity under the same normal load condition.

Abstract: Precision grinding of a multilayered thin film solar panel is recognized as the bottleneck in its manufacturing process. A primary challenge is the significantly high stress induced at the thin film interfaces during grinding. Such stress concentration can result in interfacial delamination between two dissimilar materials and thus device malfunction. This study used a finite element modelling analysis to understand the stress evolution of the multilayer thin film structure during a single grit scratching that simulates the individual interaction between abrasive grits and work materials in grinding. The results demonstrated that significant tensile and shear stresses were formed at interfaces during scratching, which could be traced back to the experimental evidence obtained from the nanoscratching process. The maximum stresses undertaken by the interfaces were simulated.

Abstract: To improve surface planarity, a translational movement is added into the magnetorheoloigcal planarization process. To explore effects of some process parameters, including trajectory type, stroke and reciprocate velocity, on surface planarity, a set of finishing experiments are carried out. The results show that planarity is well improved when the trough reciprocates perpendicularly to the air gap. Surface planarity decreases as stoke increases but is hardly affected by reciprocate velocity. Using the magnetorheoloigcal planarization process with addition of translational movement, an ultra-smooth surface with planarity of micron order in PV is achieved on a K9 optical glass.

Abstract: Thinning of the silicon wafers and decrease in kerf loss can minimize the production costs of semiconductor products. Currently, the quantity of kerf loss is about the same as the volume of the wafer itself. If we drastically reduce kerf loss, we can easily lower production costs. Therefore, we studied techniques for slicing silicon wafers with reduced kerf loss using a wire tool. As a first step, we performed micro-grooving with a fine wire tool. In this paper, we discuss the micro-grooving performance of a fine wire tool made of tungsten. A borosilicate glass is used as the work material. The main conclusions are as follows: When a fine wire tool and small-diameter abrasives are used, the kerf loss decreases. However, the strength of fine wire tools is very low. The relative velocity and abrasive diameters have a significant influence on the micro-grooving characteristics. Fine wire tools are easily fractured at fast relative velocities and with large-diameter abrasives. However, the grooving rate increases. Groove depth and grooving efficiency do not depend on the relative velocity and are dependent on the abrasive diameter.