Machining Of Titanium Alloys Research Articles

A Fuzzy Logic Model for the Analysis of Ultrasonic Vibration Assisted Turning and Conventional Turning of Ti-Based Alloy.

Titanium and its alloys are largely used in various applications due its prominent mechanical properties. However, the machining of titanium alloys is associated with assured challenges, including high-strength, low thermal conductivity, and long chips produced in conventional machining processes, which result in its poor machinability. Advanced and new machining techniques have been used to improve the machinability of these alloys. Ultrasonic vibration assisted turning (UVAT) is one of these progressive machining techniques, where vibrations are imposed on the cutting insert, and this process has shown considerable improvement in terms of the machinability of hard-to-cut alloys. Therefore, selecting the right cutting parameters for conventional and assisted machining processes is critical for obtaining the anticipated dimensional accuracy and improved surface roughness of Ti-alloys. Hence, fuzzy-based algorithms were developed for the ultrasonic vibration assisted turning (UVAT) and conventional turning (CT) of the Ti-6Al7Zr3Nb4Mo0.9Nd alloy to predict the maximum process zone temperature, cutting forces, surface roughness, shear angle, and chip compression ratio for the selected range of input parameters (speed and depth-of-cut). The fuzzy-measured values were found to be in good agreement with the experimental values, indicating that the created models can be utilized to accurately predict the studied machining output parameters in CT and UVAT processes. The studied alloy resulted in discontinued chips in both the CT and UVAT processes. The achieved results also demonstrated a significant decline in the cutting forces and improvements in the surface quality in the UVAT process. Furthermore, the chip discontinuity is enhanced by the UVAT process due to the higher process zone temperature and the micro-impact imposed by the cutting tool on the workpiece.

Study of TiB2 Coated Hard Alloy Tool Wear Resistance During Titanium Alloy Machining

Study of TiB2 Coated Hard Alloy Tool Wear Resistance During Titanium Alloy Machining

An Investigation of Cutting Performance and Action Mechanism in Ultrasonic Vibration-Assisted Milling of Ti6Al4V Using a PCD Tool.

A polycrystalline diamond (PCD) tool is employed in cutting various titanium alloys because of its excellent properties. However, improving the cutting performance of titanium alloys is still a challenge. Here, an experimental investigation on the influence of ultrasonic vibration-assisted machining (UVAM) of Ti6Al4V titanium alloy on the cutting performance and action mechanism was studied using a PCD tool. Cutting force, machined surface, surface adhesion, and wear morphology were analyzed. The results indicated that UVAM can effectively improve cutting performance. It was found that there was serious adhesion and wear of slight fragments close to the cutting edge after ultrasonic-assisted dry milling. Furthermore, the action mechanism of UVAM in improving cutting performance was discussed and analyzed from the perspective of intermittent cutting.

Comparison between the machinability of different titanium alloys (Ti–6Al–4V and Ti–6Al–7Nb) employing the multi-objective optimization

Titanium and its alloys are amongst the most important metallic materials used by many industries, such as those pertaining to the aerospace, automotive, and biomedical sectors. This is due to the reliability and functionality of titanium components, in addition to their high strength-to-weight ratio and corrosion resistance. Thus, titanium and its alloys are of great importance to the challenging operations of these sectors. The manufacturing of titanium requires great accuracy to ensure that resulting products meet quality requirements, due to its difficult machinability. In this study, the cutting forces and surface roughness of the turning were analysed to compare different titanium alloys, Ti–6Al–4V and Ti–6Al–7Nb, with CVD-coated and uncoated inserts. The effect of control factors on the response variables was measured using ANOVA. Response surface methodology was applied to the creation of a model of responses and to a bi-objective optimization process via the normalized normal constraint method. The Pareto-optimal sets of both alloys were achieved, which may be applied to practical situations to achieve optimal results for these responses. The models and optimization results confirmed the similarity of machinability values between the Ti–6Al–4 V and Ti–6Al–7Nb alloys. The uncoated inserts yielded the best surface roughness and cutting force results when used with both titanium alloys.

Enhancement of machinability and surface quality of Ti-6Al-4V by longitudinal ultrasonic vibration-assisted milling under dry conditions

Longitudinal ultrasonic vibration-assisted milling (LUVAM) was performed to improve the machinability and surface quality of titanium alloys Ti-6Al-4V under dry conditions. Effects of ultrasonic amplitude on the three-component cutting forces, cutting temperature, surface topography and 3D surface roughness (Sa and Sq) were investigated. The results show that, the cutting forces in both longitudinal and feed directions decrease with the increasing amplitude from 0 to 6 µm, as well as the average and maximum cutting temperature. Accordingly, the surface topography of Ti-6Al-4V becomes more uniform when ultrasonic amplitude reaches to 6 µm. Sa and Sq decrease by 35.1% and 34.0%, respectively, when the ultrasonic amplitude increases from 0 to 6 µm. The machinability and surface quality of Ti-6Al-4V are improved via this dry LUVAM, duo to the thermal-mechanical coupling resulted from large-amplitude ultrasonic vibration. The established approaches have potential applications in dry or near dry cutting of difficult-to-machine alloys with LUVAM.

The Influence of Polymeric Ester-Type Additives on the Performance of Metal Cutting Fluids for Machining of Titanium Alloy

The Influence of Polymeric Ester-Type Additives on the Performance of Metal Cutting Fluids for Machining of Titanium Alloy

Improving material removal rate in macro electrolyte jet machining of TC4 titanium alloy through back-migrating jet channel

In electrochemical machining (ECM), increasing the material removal rate (MRR) can improve machining efficiency. For the macro electrolyte jet machining (macro-EJM), increasing the working area of the tool front-end face can increase the MRR. However, the available tool structures cannot increase the working area of the front-end face by setting the jet channel at the center of the electrode. Therefore, to increase the working area of the front-end face, tools with back-migrating jet channels were proposed for the macro-EJM of TC4 titanium alloy in this paper. The distributions of the flow field and electric field of tools with different back-migration distances of the jet channel were numerically simulated, and experiments were carried out. Results showed that compared with the standard tool with a central jet channel, tools with back-migrating jet channels significantly increased the electricity quantity at each point on the surface of workpiece. This promoted the removal of more matrix materials from workpiece surface, improving the MRR of macro-EJM. When the back-migration distance of the jet channel was increased to 1.5 mm, the MRR increased by 41%, the machining depth increased by 33%, and the taper angle decreased by 15% compared with those of the standard tool with a central jet channel. In addition, the machining localization of the groove edge can also be improved by increasing the back-migration distance of the jet channel. When the back-migration distance of the jet channel was 1.5 mm, the reflected electrolyte was no longer in direct contact with the non-machined areas, leading to a sharp groove edge.

Multi-objective optimization of machining parameters during green machining of aerospace grade titanium alloy using Grey–Taguchi approach

This paper presents multi-objective optimization of aerospace-grade titanium alloy using the Gray–Taguchi approach. Experimentation has been conducted with varying cutting conditions according to Taguchi's L9 orthogonal array. Tool nose wear, tool flank wear, surface roughness and material removal rate are employed as process characteristics. The experimental outcomes are statistically analyzed using the Grey–Taguchi approach. Statistical and sensitivity analysis are also performed. Studies revealed that cutting speed and feed rate are having a significant influence on process performances. Micro analysis of cutting tool is also performed to study the kind of wear. Furthermore, chips were also analysed using scanning electron microscope to study its features and morphology to obtain a better insight into the process.

Investigation of a new water-based cutting fluid for machining of titanium alloys

Titanium alloys are difficult-to-cut materials and difficult to be lubricated. In this paper, a new synthetic water-based cutting fluid for titanium alloys is developed. The main ingredients which contain polar groups are easy to adsorb on titanium alloy and form a stable boundary lubricant film. The lubricating and anti-wear properties of the developed cutting fluid were tested and the results show that the use of the developed cutting fluid leads to a low friction coefficient. Moreover, the machining performance of the developed cutting fluid was further tested through tapping, milling, and drilling. The tapping torque, machining force, tool wear, and machined surface roughness were used to evaluate the cutting fluid. It was found that the developed cutting fluid could decrease both the machining force and tool wear and get good surface quality owing to its good lubricating ability for titanium alloys.

Wear and Breakage Detection of Integral Spiral End Milling Cutters Based on Machine Vision.

Tool wear and breakage detection technologies are of vital importance for the development of automatic machining systems and improvement in machining quality and efficiency. The monitoring of integral spiral end milling cutters, however, has rarely been investigated due to their complex structures. In this paper, an image acquisition system and image processing methods are developed for the wear and breakage detection of milling cutters based on machine vision. The image acquisition system is composed of three light sources and two cameras mounted on a moving frame, which renders the system applicable in cutters of different dimensions and shapes. The images captured by the acquisition system are then preprocessed with denoising and contrast enhancing operations. The failure regions on the rake face, flank face and tool tip of the cutter are extracted with the Otsu thresholding method and the Markov Random Field image segmentation method afterwards. Eventually, the feasibility of the proposed image acquisition system and image processing methods is demonstrated through an experiment of titanium alloy machining. The proposed image acquisition system and image processing methods not only provide high quality detection of the integral spiral end milling cutter but can also be easily converted to detect other cutting systems with complex structures.

Experimental Investigation on Machinability of Titanium Alloy by Laser-Assisted End Milling

The Machining of titanium alloys is challenging because of their high strength, low thermal conductivity, high chemical reactivity, and high stresses at the cutting tool edges. Laser-assisted machining is an effective way to improve the machinability of titanium alloys. This paper presents an experimental investigation of the machinability of cutting force and surface roughness in laser-assisted end milling of titanium alloy Ti-6Al-4V. The absorptivity of Ti-6Al-4V was determined by conducting preheating experiments using a high-power diode laser with a wavelength of 940–980 nm. A thermal analysis was performed using the finite element method to predict temperature distribution. The depth of cut was determined where tensile strength decreased sharply, and the predicted surface temperature is presented in the analysis results. The experiments were performed with conventional machining and laser-assisted machining. Surface roughness, tool wear, and cutting force were evaluated. In contrast to the results of conventional end milling, laser-assisted end milling improved surface roughness. Moreover, laser-assisted end milling proved more effective than conventional end milling in terms of cutting tool damage. Our results proved that heat assistance significantly influenced the magnitude of the cutting forces—while the actual reduction in forces varied slightly depending on the force component, cutting tool, and cutting conditions, force components showed a reduction of roughly 13–46%.

Analysis of abrasive belt wear effect on residual stress distribution on a grinding surface

Owing to elastic grinding and other favorable processing characteristics, belt grinding has been widely used in many industrial applications, including machining titanium alloys of difficult-to-cut metals. Abrasive belt wear inevitably occurs in the grinding process, but its mechanism and effects have not been fully understood, especially its effect on the residual stress (RS). To overcome this shortcoming, this study experimentally investigates the abrasive wear influence on the surface RS distribution of titanium plate belt grinding through a synthetic cause analysis. First, abrasive belts with different wear stages are prepared according to the wear law throughout the abrasive belt life cycle, and their wear degrees are quantitatively evaluated. Then, comparative grinding experiments of the TC4 flat plate are conducted using the prepared abrasive belts. Finally, the surface RS distribution of the grinding traces and stress differences induced by the abrasive belt wear are analyzed and discussed comprehensively. The results indicate that the more severe the abrasive belt wear is, the greater the accumulation of grinding heat and the greater the ratio of the grinding energy will be, which will further lead to residual tensile stress (RTS) generation, especially in the grinding direction. In addition, owing to the fast heat dissipation on both sides of the contact wheel, the surface RS along the grinding traces' vertical direction obeys an approximately symmetrical distribution, having low values on the sides and a peak in the middle. The strong accumulation of grinding heat caused by severe wear makes the difference between the stress distribution extremums increase with the abrasive belt wear.

Research on micro-texture placement position and cutting performance of negative chamfering ball-end milling cutter

In order to optimize the position of the micro-texture on the negative chamfering edge ball-end milling cutter, the experiment of milling titanium alloy with the negative chamfering micro-texture ball-end milling cutter was carried out. The effects of micro-texture at different placement positions (rake and flank faces of cutting tools) on cutting performance were compared when the cutting depth was 0.3 mm, and the effects of negative chamfering and micro-texture parameters on cutting performance of the cutter were studied. Finally, the negative chamfering and micro-texture parameters were optimized based on genetic algorithm. The results show that the micro-texture of the flank face can improve the cutting performance, and the negative chamfering angle and width have the greatest influence on the cutting performance. The parameter optimization results are: the negative chamfering angle is 10.016°, the negative chamfering width is 199.995 μm, the micro-pit diameter is 49.996 μm, the micro-pit spacing is 174.004 μm, and the micro-pit distance from the edge is 109.993 μm. The above research realizes high efficiency and high-quality machining of titanium alloy.

Study on design, manufacture, and cutting performance of circular-arc milling cutters for machining titanium alloy

Titanium alloy is widely used for manufacturing structural parts of high-end equipment due to its excellent mechanical properties, despite difficulty in being machined. Nowadays, titanium alloy parts are mostly machined by ball-end milling cutters (BEMC), but the cutting edge structure of the BEMC limits the improvement in machining efficiency and surface quality of the parts. In this paper, a circular-arc milling cutter (CAMC) with large-curvature cutting edge was proposed; the differential geometry method was used for establishing the geometric model for the contour surface of the CAMC and the mathematical model for the spiral cutting edge line; the conversion matrix between grinding wheel and workpiece coordinates was introduced to derive the equation of grinding wheel trajectory when the rake face of the CAMC was ground; the self-designed CAMC was ground and tested in accuracy. The comparative research was conducted experimentally on the side milling of titanium alloy TC4 with the CAMC and BEMC, and consequently the variation laws of milling forces, wear morphology, and machined surface quality were obtained about the two types of milling cutters. The results indicated that the CAMC can effectively reduce the main milling force and keep the milling process stable. Moreover, the CAMC was worn slower and produced better surface quality than the BEMC.

Influence of Internal Structure on the Machining of VT6 Titanium Alloy Produced by Additive Technology

Influence of Internal Structure on the Machining of VT6 Titanium Alloy Produced by Additive Technology

High-temperature wear behavior of micro- and ultrananocrystalline diamond films against titanium alloy

In the present study, we conducted tribological experiments to study the wear behavior of micro- (MCD) and ultrananocrystalline diamond (UNCD) films against titanium alloy at temperatures up to 700 °C. We found that at comparatively low temperatures (25–500 °C), the wear of diamond films is basically induced by the strong adhesion between diamond and titanium, which promotes the formation of Ti C bonds and detaches the carbon atoms from the diamond surface. When the temperature increases to 600 °C, oxygen starts to significantly etch the diamond films, producing gaseous CO/CO 2 and causing more loss of carbon atoms. At 700 °C, the UNCD film is systematically etched by oxygen, and the film is dominated by WO 3 , with drastically decreased wear resistance. The MCD film still maintains certain wear resistance at 700 °C, but it is also severely etched by oxygen, with substantially shrunk MCD grains. This work provides significant insights into the high-temperature wear behavior of diamond films and the application of diamond-coated cutting tools for machining titanium alloy and other high-cutting-temperature materials. • Adhesive wear and oxidation are main wear patterns of microcrystalline (MCD) and ultrananocrystalline diamond (UNCD) films • Adhesive wear can be induced by the formation of interfacial Ti-C bonds • Both MCD and UNCD films are substantially etched by oxygen when the temperature is higher than 600 °C • Drastic decrease of wear resistance occurs in UNCD films at 700 °C due to the intense oxidation of the UNCD film

Recast Layer Formation during Wire Electrical Discharge Machining of Titanium (Ti-Al6-V4) Alloy

Recast Layer Formation during Wire Electrical Discharge Machining of Titanium (Ti-Al6-V4) Alloy

Research progress on formation mechanism of surface integrity in titanium alloy machining

Titanium alloy is the main application material for the key components of aero-engine due to its excellent properties, such as light weight, high strength, high temperature resistance, and fatigue resistance. Because of its small elastic modulus, low thermal conductivity, and strong chemical affinity, it produces greater cutting force and higher cutting temperature in the machining process. Different thermal mechanical coupling effects can change the surface structure, composition, and mechanical properties of the material, resulting in different surface integrity state characteristics. This paper expounds the effects of process parameters, tool materials and properties, and lubrication methods on cutting force, cutting temperature, surface roughness and morphology, residual stress, microhardness, and microstructure based on the formation mechanism of surface integrity. It is pointed out that the existing researches mainly focus on the description of phenomena and laws. The research on the formation mechanism of surface integrity based on the thermal-mechanical coupling on the processing interface is lack, and the qualitative characterization system of surface integrity is not perfect. Therefore, the object of titanium alloy machining needs to be upgraded from test block to component, and the influence of the change of contact state of the processing interface caused by the time-varying machining trajectory on the surface integrity should be considered. Moreover, the quantitative evaluation of plastic deformation and grain characteristics is completed to accurately predict the gradient distribution of surface integrity. Taking fatigue performance as the goal, the surface integrity distribution meeting the service performance of components is deduced and designed, and then the processing conditions meeting the requirements are determined to realize the surface integrity processing.

Characterization of electric discharge machining of titanium alloy utilizing MEIOT technique for orthopedic implants

In this research work, medical grade titanium alloy Ti4Al6V was electric discharge machined with an objective of attaining mirror finish for orthopedic implants. Experiments were conducted by varying tool materials, discharge current, pulse on time and pulse off time whereas the responses chronicled are material removal rate, electrode wear rate and surface roughness. The aluminium (A), copper (C) and aluminium alloy reinforced with graphite particles of various weight percentage (5-A1,10-A2,15-A3) were used as tool materials. The composites were fabricated using stir casting technique. The findings showed that the titanium alloy machined with A1 composite tool offers the highest MRR, the C tool has the lowest EWR, and the A2 composite tool results in good surface finish. The surface of specimens produced using A1 tool exhibits poor surface quality owing to the eczema surface. Specimens machined with the C tool have a remelted layer, pockmarks, and an uneven fusion structure, which were not present in specimens machined with the A2 tool. MOORA-ELECTRE Integrated Optimization Technique (MEIOT) was applied to select the best parametric combination and the best electrode material.

Machining of titanium alloys for medical application - a review

Titanium alloys for their characteristics have acquired a prominent position in numerous industrial applications. Due to its properties, such as high resistance to corrosion, reduced density, high specific strength, and low Young’s modulus, titanium alloys became indispensable as a biomaterial with high use in medical devices, with special emphasis in the area of orthopedics. Problems associated with its manufacturing by conventional machining processes, such as milling, turning, and drilling are well known and studied. Its low thermal conductivity, high chemical reactivity, high hardness at high temperatures make it classified as difficult to machine material. Despite the already extensive knowledge about machining titanium alloys problems, and the constant technological development to overcome them, it is not yet possible to machine this material like other metals. This work is based on research and review papers from Scopus and Scholar from 2010 to 2020 and addresses the main issues related to the machining of titanium alloys used in medical devices manufacturing and current solutions adopted to solve them. From the research consulted it was possible to conclude that it is consensual that for milling, turning, and helical milling cutting speed can reach up to 100 m/min and up to 40 m/min in drilling. As for feed rate, up to 0.1 mm/tooth for milling and helical milling and up to 0.3 mm/rev for turning and 0.1 mm/rev for drilling. Also, that Minimum Quantity Lubrication is a valid and efficient solution to mitigate titanium alloys machining problems.