Experimental Investigation on the Advantages of Dry Machining over Wet Machining during Turning of AISI 1020 Steel

In this study, the experiment was conducted to investigate the advantage of dry machining over wet machining during turning of AISI 1020 steel using cemented carbide tool on a CNC lathe machine. Surface roughness and cutting temperature were measured by VOGEL surface roughness tester and infrared thermometer respectively. The experiments were conducted based on Taguchi L9 orthogonal array design. Surface roughness, cutting temperature, tool life, and machining cost were analyzed graphically. The average surface roughness and cutting temperature achieved with wet machining was 2.01 μm and 26.540C, which was 17.41% and 44.86% respectively, lower than dry machining. The high cutting temperature in dry turning result in short tool life, which was 41.15% shorter than wet turning. The machining cost of wet turning was about 56% greater than the cost of dry turning. The cost of coolant in wet turning is 42.88% greater than that of the cutting tools. The highest cost was shared by tool cost, which was 81.33% of the total cost for dry turning, while 70.00% of the total cost was shared by coolant cost for wet turning. Results revealed that dry turning is more economical than wet turning.

Influence of Graphene Nanosheets on Thermo-Physical and Tribological Properties of Sustainable Cutting Fluids for MQL Application in Machining Processes

This study investigates the effects of applying two vegetable and one mineral-based cutting fluids with 0.05 %wt and 0.1 %wt dispersion of graphene sheets on the tribosystem generated at the interface between the cemented carbide tool and the AISI 1045 steel workpiece. The fluids are firstly characterized (viscosity, thermal conductivity and diffusivity, and wettability) and tested in reciprocating and ramp milling tests. The results show that the graphene sheets alter the thermo-physical and tribological properties of the cutting fluids; in this case, vegetable-based cutting fluids, even in minimum quantities and with graphene nanoparticles, have a high potential for increasing the efficiency and sustainability of the milling process.

Manufacturing of high-precision surface micro-structures on stainless steel by ultrasonic impact peening

Ultrasonic impact peening (UIP) is not only a mature technique of surface treatment, but also a promising method of surface texturing for promoting performance and functionalities of components and devices. In the present work, we demonstrate the feasibility of applying UIP in the manufacturing of high precision surface micro-structures on 316L stainless steel using a YG6 cemented carbide tool. Specifically, analytical investigation of the material deformation map under UIP is carried out, which is validated by corresponding finite element simulations based on a combined nonlinear isotropic/kinematic hardening model, as well as experiments performed on home-made UIP apparatus. Finally, surface micro-structures of aligned grooves with a depth of 2 µm and a periodicity of 240 µm are fabricated by using UIP, and are subsequently subjected to linear reciprocating ball-disk sliding tests. Corresponding experimental results show that the micro-structures fabricated by UIP possess comparable accuracy of groove morphology and frictional properties with that fabricated by using ultrasonic elliptical vibration cutting using a single crystal diamond tool. The present work sheds lights on the low-cost fabrication of high precision surface micro-structures on ferrous metals by mature UIP technique.

Investigation on hardness testing of cemented carbide tool based on finite element method

Hardness is a critical mechanical property of cutting tools, which significantly affects the cutting performance and wear resistance. Therefore, it is of great significance to obtain the hardness of the tool surface accurately. This paper presents a method based on finite element method (FEM) for studying the hardness of carbide tools. The microstructure of the carbide tool is obtained by scanning electron microscope(SEM). Combined with stereo principle, and secondary treatment, a three-dimensional multi-crystal model of carbide tool and indentation is established, and the model and hardness value obtained by different calculation methods are verified by microhardness test. The results show that the real hardness of the cemented carbide tool can be obtained by the indentation FEM model. The hardness values of cemented carbide tools are then calculated by the traditional method, Oliver-Pharr (OP) method and indentation method, respectively. It is found that the hardness value of the traditional method is the largest and fluctuates greatly, while the hardness values calculated by the OP method and indentation method are similar, and the fluctuation range of the hardness value calculated by the OP method is larger. In conclusion, the hardness calculated by the indentation work method is the best.

Assessment of wear micromechanisms on a laser textured cemented carbide tool during abrasive-like machining by FIB/FESEM

The combined use of focused ion beam (FIB) milling and field-emission scanning electron microscopy inspection (FESEM) is a unique and successful approach for assessment of near-surface phenomena at specific and selected locations. In this study, a FIB/FESEM dual-beam platform was implemented to docment and analyze the wear micromechanisms on a laser-surface textured (LST) hardmetal (HM) tool. In particular, changes in surface and microstructural integrity of the laser-sculptured pyramids (effective cutting microfeatures) were characterized after testing the LST-HM tool against a steel workpiece in a workbench designed to simulate an external honing process. It was demonstrated that: (1) laser-surface texturing does not degrade the intrinsic surface integrity and tool effectiveness of HM pyramids; and (2) there exists a correlation between the wear and loading of shaped pyramids at the local level. Hence, the enhanced performance of the laser-textured tool should consider the pyramid geometry aspects rather than the microstructure assemblage of the HM grade used, at least for attempted abrasive applications.

Influence of Cemented Carbide Composition on Cutting Temperatures and Corresponding Hot Hardnesses

During metal cutting, high temperatures of several hundred-degree Celsius occur locally at the cutting edge, which greatly impacts tool wear and life. Not only the cutting parameters, but also the tool material’s properties influence the arising cutting temperature which in turn alters the mechanical properties of the tool. In this study, the hardness and thermal conductivity of cemented tungsten carbides were investigated in the range between room temperature and 1000 °C. The occurring temperatures close to the cutting edge were measured with two color pyrometry. The interactions between cemented carbide tool properties and cutting process parameters, including cutting edge rounding, are discussed. The results show that cemented carbides with higher thermal conductivities lead to lower temperatures during cutting. As a result, the effective hardness at the cutting edge can be strongly influenced by the thermal conductivity. The differences in hardness measured at room temperature can be equalized or evened out depending on the combination of hardness and thermal conductivity. This in turn has a direct influence on tool wear. Wear is also influenced by the softening of the workpiece, so that higher cutting temperatures can lead to less wear despite the same effective hardness.