Authors: Bang Yan Ye, Jin Xu, Xiao Chu Liu, Yan Ming Quan
Abstract: In this article, the micro-topography and texture characteristics of machined surface
under the condition of high speed cutting are analyzed based on experimental observation. The forming process of machined surface and cause of the appearance are also discussed. The experimental results show that furrow and ridges, surface white layer and molten metal daub by the feed motion of cutting tool are found on machined surface due to the effect of high cutting temperature and rotating of workpiece in high speed turning process.
238
Authors: Armansyah Ginting, Mohammed Nouari, Nadhir Lebaal
Abstract: In this paper, the surface integrity is studied when machining the aeronautical titanium alloys. Surface roughness, lay, defects, microhardness and microstructure alterations are studied. The result of surface roughness judges that the CVD-coated carbide fails to produce better Ra value than the uncoated. Lay is characterized by cutting speed and feed speed directions. Feed mark, tearing surface, chip layer formation as built up layer (BUL), and deposited microchip are the defects. Microhardness is altered down to 350 microns beneath the machined surface. The first 50 microns is the soft sub-surface caused by thermal softening in ageing process. Microstructure alteration is observed in this sub-surface. Down to 200 microns is the hard sub-surface caused by the cyclic internal work hardening and then it is gradually decreasing to the bulk material hardness. It is concluded that dry machining titanium alloy is possible using uncoated carbide with cutting condition limited to finish or semi-finish for minimizing surface integrity alteration.
1059
Authors: Bao Yun Qi, Ning He, Liang Li, Wei Zhao
Abstract: It is commonly believed that the white layer formed during hard machining of steels is caused primarily by a thermally induced phase transformation resulting from rapid heating and quenching. The focus of this study is to investigate the white layers produced on the machined surfaces and on the inner side part of the chips in dry hard turning GCr15 with PCBN tools. Samples of machined workpiece and chips were metallographically processed and observed under a microscope to determine whether white layers were present or not. Some properties of white layers were deduced in order to verify some of the prevalent theories. More specifically, chip shapes were studied to determine how they developed during machining with potential appearance of white layers, with a view to correlating the chip shapes with the white layer formation.
241
Authors: Jin Ming Zhou, Volodymr Bushlya, Ru Lin Peng, Jan Eric Stahl
Abstract: There is considerable industrial significance to understand the nature of subsurface deformation under the machined surface for correct prediction of surface properties in machined components based upon the machined conditions and material behaviors that give rise to them. In this study, high speed machining of Inconel 718 was carried with whisker reinforced ceramic cutting tool under different conditions of tool wear, coolant state and cutting parameters. The objective of the present investigation was to determine the effect of both cutting parameters and tool wear on the plastic deformation in the subsurface region of Inconel 718 after the finishing machining with above process conditions. The surface and subsurface region of machined specimens were examined using a high resolution scan electron microscope (HRSEM) and EBSD technique, microhardness measurements were also conducted on the test samples, accordingly plastic strain analysis were carried out.
1681
Authors: Yang Qiao, Xing Ai, Zhan Qiang Liu
Abstract: Powder metallurgy (PM) nickel-based superalloy is regarded as one of the most important aerospace industry materials, which has been widely used for engine components. As the demands of the service performance increase, the surface characteristics are becoming more and more important. However, the machined surface of PM nickel-based superalloy is easily damaged due to its poor machinability. A series of milling experiments in a wide range of speeds were carried out to investigate the effects of dry milling parameters on the surface characteristics of PM nickel-based superalloy. The machined surface is evaluated in terms of surface roughness and work hardening. The results show that, milled surface characteristics of PM nickel-based superalloy are sensitivity to the cutting speeds. The machined surface roughness increases with increase of the cutting speed, but with further increase of cutting speed between 70 to 90 m/min and 150 to 170 m/min two decreases in surface roughness appear. For work hardening, it can be seen that the machined workpiece surface hardens seriously.
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