Key Engineering Materials Vols. 407-408

Abstract: Ti6Al4V is a difficult to machine alloy with low cutting efficiency and server tool wear. A series of orthogonal turning tests with CBN (Cubic Boron Nitride) in higher speed scale was carried out on a CA6140 lathe. The experiential functions of tool life based on orthogonal experiment were developed. The tool wear morphologies were examined by scanning electron microscope (SEM) and energy disperse spectroscopy (EDS), adhesion, diffusion and micro-chipping were the major wear mechanisms of CBN tool. Finally, the cutting parameters of CBN tool in Ti6Al4V dry turning were optimized based on tool life-efficiency contour analysis, in same cutting efficiency, the higher cutting speed and small depth of cut are the better selection, it means that utilization of CBN tool enables the high cutting speed turning of Ti6Al4V.

Abstract: To accurately simulate the segmented chip formation of titanium alloy Ti6Al4V in high speed cutting process, the key techniques of the finite element modeling were investigated detailed, which included establishing the finite element model, material constitutive relation, chip separation criteria, material failure criteria. A high speed cutting case of titanium alloy Ti6Al4V were simulated with thermal mechanical analysis and adiabatic analysis respectively. Through the comparison of the two simulated results, it proved the segmented chip is formed because of the adiabatic shear. The results prove the finite element model established is correct.

Abstract: Micro carbide endmills suffer severe abrasive friction and impact wear in high speed milling of graphite. This paper focused on the study of the effect of Co content and WC grain size on the tool wear resistance of micro carbide endmills in high speed milling of graphite. The tool wear morphologies of cutting tools were examined at the initial wear stage and severe wear stage. The results showed that the abrasive resistance of micro carbide endmill increased with the decrease of Co content and WC grain size. The best impact resistance can be obtained with medium Co content and smaller WC grain size. The fine-grained carbide 0.2WC-8%Co is considered as the optimum tool material for high speed milling of graphite.

Abstract: Taguchi design methodology is applied to experiments of flank mill machining parameters of titanium alloy TC11 (Ti6.5A13.5Mo2Zr0.35Si) in conventional and high speed regimes. This study includes three factors, cutting speed, feed rate and depth of cut, about two types of tools. Experimental runs are conducted using an orthogonal array of L9(33), with measurement of cutting force, cutting temperature and surface roughness. The analysis of result shows that the factors combination for good surface roughness, low cutting temperature and low resultant cutting force are high cutting speed, low feed rate and low depth of cut.

Abstract: Nowadays, an increase on demands of aerospace components has led to implementation of high speed machining (HSM). The principal factors in the performance of aerospace materials are strength-to-weight ratio, fatigue life, fracture toughness, survivability and of course, reliability. However, when HSM is coupled with dry or near dry machining, it will present considerable technical challenges to the manufacturing sector especially when the integrity of the machined surface is concerned. In this investigation, the effect of high speed drilling (HSD) conditions on the performance and surface integrity of Inconel 718 were studied. Hole was drilled individually using TiAlN coated carbide insert drill (14 mm in diameter) under minimum quantity of lubrication (MQL) condition. Results showed that uniform flank wear and chipping were the dominant tool failure modes. Moreover, the results showed an increase in cutting temperature with increasing cutting speed and feed rate. Thrust force and torque decreased linearly with the increasing cutting speed but significantly increased when higher feed rate is employed. Cutting speed significantly influenced the distribution of surface roughness value. Variations of hardness readings were recorded beneath the machined surfaces, they were due to the hardening effects caused by concentration of high temperature and stresses on the workpiece.

Abstract: In order to remove the reaction products generated from the interelectrode gap of the electrochemical micro-machining, an angle adjustable electrochemical micro-machining equipment has been developed, which consists of angle adjustment unit, feed system unit, etc. Small holes have been drilled on thin stainless steel 304 by using our developed equipment. The experimental results show that the adjusted cathode working angle and high speed of cathode rotation improves micro-ECM performance characteristics.

Abstract: A newly surface treatment method was proposed by the combination of the high-speed laser scanning with Galvano scanner and the single-mode pulsed fiber laser with Master Oscillator Power Amplifier, and various periodic structures could be formed by this technique. The surface roughness of irradiated area increased almost proportionally with increasing the number of laser scan, and it could be controlled by the number of scan. The repellency of surface could be increased by the laser irradiation compared to that of ground surface under nitrogen atmosphere condition, while the hydrophilic property of surface could be improved by the laser scanning under air atmosphere condition. Moreover, it was found that the corrosion resistance of the surface could be improved by laser irradiation.

Abstract: Sintered NdFeB magnet is widely used in many areas because of its excellent magnet. This paper studies the effect of ultrasonic vibration of tool on electrical discharge machining of it. Experiments were carried out on self-made equipment and material removal rate(MRR) against pulse-on time, MRR versus peak current and machined surface results with and without ultrasonic employment were analyzed. Results show that MRR of the ultrasonic assisted electro-discharge machining would be up to five times higher than MRR of the conventional EDM for small pulse durations and low discharge currents. The machined surface of US/EDM is finer than EDM because of less arcing and short circuit pulses. There are less cracks on the surface.

Abstract: The specification of the vibration cutting loading is a decision factor for the generation of stress wave and the stress wave propagation has a significant impact on its micro-mechanism. Making the stress waves’ generation in the cutting area of vibration cutting for entry point, the analysis of internal inflection wave, inflection fracture and dynamic stress intensity factor has been carried out, the simulation of vibration cutting has also been done by finite element method, the essential of energy concentrated role, shear angle increment and cutting quality improvement has been explained.

Abstract: This paper deals with EDM characteristics of newly develops electrically conductive ceramics. Titanium boride (TiB2) is widely used as die and mold materials because of its high hardness, high-temperature resistance and so on. The EDM characteristics of the titanium boride, such as electrode wear rate, removal rate and surface roughness were investigated. Experimental results show that EDM with low electrode wear rate is possible when copper electrode is used with positive polarity. The removal rate becomes much higher when graphite electrode is used with negative polarity.