Investigation on the Machinability of Metastable β Titanium Alloy M28

Oriented to the application of new generation strategic aircraft, M28 (Ti-4Al-5Mo-5V-6Cr-1Nb) is a novel metastable β titanium alloy with outstanding strength. A better understanding of its machinability is the cornerstone of the manufacture. In this work, milling experiments were made with the uncoated WC-Co carbide insert to investigate its machinability. Compared with milling Ti-6Al-4V, the cutting force is much higher and the tool life is considerably shorter in the milling of M28, especially in the high-speed cutting. Serious edge breaking is found at normal cutting speed. While a continuous band of flank wear with significant chip adhesion, which covers comb cracks in the cutting edge, is found in the high-speed cutting tool. The machinability of M28 is considerably poorer than that of Ti-6Al-4V. The hard-to-machine performance of M28 is considered to be subject to the material property of the metastable β titanium alloy as well as the competing mechanism among work hardening, strain rate hardening and the thermal softening in the cutting. According to the detection of the scanning electron microscope (SEM) and the energy dispersive spectrometer (EDS), the diffusion of C and Co generates a negative influence on the cutting edge and accelerates the tool wear.

Drilling of Additive Manufactured Poly Lactic Acid Modified byDrilling of Additive Manufactured Poly Lactic Acid Modified by Ultrasonic Vibration Ultrasonic Vibration

Complex geometries can be produced by using additively manufacturing method (AM). As usual, the AM parts have rough surfaces in which post processing operations are needed. One of the useful operations is ultrasonic drilling process. In this process, an additional movement is added to the cutting tool to improve the machinability factors. In this study, poly lactic acid(+) was selected as workpiece where the quality of the holes generated by ultrasonic drilling, were investigated. The examination parameters were delamination, circularity, and cylindricality. As a result, it was shown that UD process could properly improve the examination parameters. It was explained that harmonic movement of drill bit in UD improved the stability of the process by a decrease in cutting forces and chip adhesion. Moreover, a significant reduction was observed in delamination factor by using ultrasonic vibrations.

Improvement of Removal Rate of Tape Lapping by Applying Fluid with Ultrasonic Excited Cavitation

Lapping with a lapping tape refers to a finishing process in which a new tape is continuously supplied to its processing area and pressed down with a pressure roller during its relative motions. In response to the growing demand for lapping high-hardness materials with high efficiency, lapping tapes with superabrasive grains formed in a textured structure with a bond have been recently utilized. In this study, we supply a working fluid that has passed through the slit between ultrasonically oscillating blades to processing points. Variations of sound pressure generate cavitation in the working fluid. Impulse waves due to the collapse of cavitation bubbles inhibit chips from getting adhered to the chip pockets of the lapping tape. We have lapped hardened SUJ2 with plural lapping tapes of different characteristics. In lapping with a lapping tape using diamond abrasive grains, we have improved the time constant for the changes in surface roughness in relation to the lapping time from 18.9 s to 7.6 s by superimposing ultrasonic oscillations; consequently, the lapping speed improved. We have compared the effects of ultrasonic oscillations for three types of lapping tapes and discovered that fewer abrasive grains and lower chip adhesion firmness due to the abrasive grains formed in a textured structure increased the effects of ultrasonic oscillations.

Fundamental Machining Characteristics of Ultrasonic-Assisted Electrochemical Grinding of Ti–6Al–4V

The Ti–6Al–4V is a widely used alloy in the aerospace industry. In order to improve the grindability of Ti–6Al–4V, a hybrid material removal process is proposed in this study. This process is a combination of ultrasonic assisted grinding (UAG) and electrochemical grinding (ECG), hereafter called ultrasonic assisted electrochemical grinding (UAECG). For confirming the feasibility of the proposed technique, an experimental setup was constructed and the fundamental machining characteristics of UAECG in the grinding of Ti–6Al–4V were experimentally investigated. The results obtained from the investigation can be summarized as follows: (1) the normal and tangential forces in UAECG were decreased approximately 57% and 56%, respectively, comparing with conventional grinding (CG). (2) The work-surface roughness Ra both in ECG and UAECG was negative correlation to the electrolytic voltage, UI, and the surface damage; (3) the wheel radius wear in UAECG was considerably smaller than that in ECG when UI < 10 V. The chip adhesion and the grain fracture mainly affected the working lives of the wheels in ECG and UAECG, whereas the wheel wear in CG was predominantly attributed to the grain drop out; (4) a titanium dioxide (TiO2) layer, which had a 78 nm thickness was achieved on the work surface in the condition of UI = 20 V, leading that the Vickers microhardness of work surface in ultrasonic assisted electrochemical was lower than that in CG by 15%.

Investigation of Grinding Fluid for Prevention of Chip Adhesion in Miniature Drilling of Glass Plate Using Electroplated Diamond Tool

In the hole drilling process, produced chip cannot be released from the inside hole which leads to broken glass plate due to the adhered chip on tool. Chip discharge method was announced by many researchers. However, the method using the tool-only with drilling command is rarely seen. In this laboratory, we have developed a tool in order to discharge chip. The developed tool is capable in preventing chip adhesion and producing high quality and efficient hole drilling process. The developed tool has several hundred times longer tool life than a conventional tool. However, the amount of adhered chips on cutting tool increase as the number of hole drilling process increases. The chip adhesion condition is different according to the kind of grinding fluid. Adhesion of chips on tool can be related to the properties of grinding fluid. Thus, in this study, the types of grinding fluid used during the hole drilling process were investigated to determine the state of chip adhesion. Three types of grinding fluid used are Emulsion, Soluble and Solution and all of them include surfactant which is considered to have an effect on prevention of chip adhesion. The main conclusions obtained in this study are as follows. Chip adhesion state was investigated after drilling process and it was found that instead of grinding fluid properties, surfactant also has significant effect on chip adhesion on tool by absorbing the adhered chip from the tool. The results showed that grinding fluid with long-chain surfactant has small amount of chip adhesion whereas grinding fluid with short-chain surfactant has large amount of chip adhesion. Therefore, it can be concluded that grinding fluid with long-chain surfactant is capable in preventing chip adhesion during hole drilling process.

Chip Adhesion and Tool Wear in Driven Rotary Cutting of Stainless Steel

In driven rotary cutting of stainless steel, adhesions sometimes occur on the tool, causing increased wear. The type of coolant supplying methods and tool rotation speed affects largely on the adhesion because it depends on the temperature and lubricating performance. Results showed that in a circumferential velocity ratio of 1.0, which means tangential component of tool peripheral speed is equal to work surface speed, there is no adhesion on the tool after cutting. In a circumferential velocity ratio of 2.0, adhesion occurred with overcooling of the flood coolant, and wear increased by adhesions to the rotating tool. It was found that the thermal cracks on the cutting edge was one of the factors of increased wear and chipping. Adhesives on the tool edge also accelerated the chipping.