Titanium Alloy Workpiece Research Articles

Study on Surface Layers of Aluminum and Titanium Alloys and Analysis of their Scuff Resistance

To reduce the risk of scoring copper or zinc coatings were applied to the samples in molten salts at a temperature of 350-500°C. Using ion sputtering and Auger electron spectroscopy the depth of the surface layers and the grain size in the coating were determined. Samples were plates 0.5-0.7 mm thick made of titanium and aluminum alloys. For copper-coated alloys a coating zone up to 10 μm and a diffuse zone up to 6 μm which is intermediate between the coating and the substrate can be distinguished in the surface layers. For zinc-coated aluminum alloys there is one zone of 5-7 μm which is an aluminum-zinc alloy of variable composition across depth. Thus, a soft metal formed on the surface of the titanium and aluminum alloys when processed in the salt melt is connected to the base metal with metallic bonds. Moreover, the higher the temperature and the longer the holding time in the salt melt, the thicker the coating is. While investigating the score resistance a dependence of the friction moment change on the path travelled to a score appearance was obtained. It has been established that the score resistance of the titanium and aluminum alloys is directly dependent on the inhomogeneity factor which is sharply increased when there is a softer (compared with the base metal) coating on the surface of the metal processed. Experimental stamping-drawing of cups made of the titanium alloy workpieces preliminary copper-coated in the salt melt was carried out. The production cycle was significantly reduced, and the surface quality of the products after the coating removal was high, the scoring was not observed. Thus, the use of soft (compared with the base metal) metal coatings applied in salt melts is promising for titanium and aluminum alloys.

Design, preparation and characterization of iron nitride magnetic abrasives

In order to effectively polish the surface of the titanium alloy workpiece, a novel type of iron nitride magnetic abrasives was designed, prepared and characterized. Theoretically, first-principles were used to analyze the effects of phase compositions of iron nitrogen compounds on the mechanical and magnetic properties of the abrasive, and ε-Fe3N and γ′-Fe4N were determined as the grinding phase compositions with the simultaneously improved properties of hardness, ductility and magnetism. In the experiments, the core-shell structured iron nitrogen compounds were prepared by nitriding the iron powders of about 250 μm with ammonia at 600 °C, and the effects of nitriding time, ammonia pressure and cooling method on the product were investigated. The composition, morphology, magnetic properties and mechanical properties of the product were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), magnetometer and nanoindenter, respectively. Under experimental conditions of ammonia pressure of 0.2 Mpa, nitriding time of 3 h and water quenching, the abrasive was obtained with the external grinding phase of ε-Fe3N and γ′-Fe4N in a thickness of 35.10 μm and the internal ferromagnetic phase of α-Fe. Its magnetic saturation intensity and hardness were 148.5 A m2 kg−1 and 8.15 GPa, respectively. Grinding with this abrasive, the surface roughness of Ti–6Al–4V alloy plate was effectively reduced from 0.305 μm to 0.077 μm.

Analysis of Chip Reduction Coefficient in Turning of Ti-6Al-4V ELI

Titanium alloys are generally used in aerospace industries due to its ability to retain its high strength at elevated temperatures. Present paper deals with Taguchi optimization approach applied to optimize process parameter in turning of Ti-6Al-4V ELI (grade 23) titanium alloy workpiece with coated carbide tool under dry condition. The trails carried out by employing L9 orthogonal array. Linear regression modelling was adopted to develop a model for prediction of experimental results. The predicated results lay proximal to the experimental value. Main effects plot and ANOVA are used to analyse the effect of input variables namely speed (v), feed (f) and depth of cut (d) on chip reduction coefficient. The optimal parameter setting obtained for chip reduction coefficient is d3-fl-vl i.e (d = 0.4 mm; f = 0.04 mm/rev; v = 46 m/min).

An Improved Abrasive Flow Processing Method for Complex Geometric Surfaces of Titanium Alloy Artificial Joints

Precise processing for complex geometric surfaces of titanium alloy artificial joints has higher technical difficulties. This paper addresses the matter by proposing an improved abrasive flow processing method. According to the micro-cutting principle, the processing mechanism on curvature surface of the titanium alloy workpiece by the abrasive flow is analyzed. A new material removal model of abrasive flow is proposed to reveal the processing regularities for complex geometric surfaces of titanium alloy artificial joints. Based on the model, in combination with the realizable k-ε turbulence model, the total force affecting on a wall region of constrained flow passage is obtained to estimate the quantity of material removal. A multi-segment profiling constrained flow passage is designed, and an optimized flow passage scheme is provided. Numerical results show that the optimized flow passage can improve the pressure/velocity profile uniformities of abrasive particles; by the product of velocity and pressure, the cutting coefficient for complex surface is obtained. A processing experimental platform is developed, and the processing experiment results indicate that the proposed material removal model can estimate the processing effects and removal regularities, and the size accuracy and surface quality of the titanium alloy surface are improved.

Tool Condition Monitoring in Micro-End Milling using wavelets

In this work, Tool Condition Monitoring (TCM) strategy is developed for micro-end milling of titanium alloy and mild steel work-pieces. Full immersion slot milling experiments are conducted using a solid tungsten carbide end mill for more than 1900 s to have reasonable amount of tool wear. During the micro-end milling process, cutting force and vibration signals are acquired using Kistler piezo-electric 3-component force dynamometer (9256C2) and accelerometer (NI cDAQ-9188) respectively. The force components and the vibration signals are processed using Discrete Wavelet Transformation (DWT) in both time and frequency window. 5-level wavelet packet decomposition using Db-8 wavelet is carried out and the detailed coefficients D1 to D5 for each of the signals are obtained. The results of the wavelet transformation are correlated with the tool wear. In case of vibration signals, de-noising is done for higher frequency components (D1) and force signals were de-noised for lower frequency components (D5). Increasing value of MAD (Mean Absolute Deviation) of the detail coefficients for successive channels depicted tool wear. The predictions of the tool wear are confirmed from the actual wear observed in the SEM of the worn tool.

Machinability of titanium alloy (Ti-6Al-4V) in environmentally-friendly micro-drilling process with nanofluid minimum quantity lubrication using nanodiamond particles

This paper discusses the experimental characterization on micro-drilling process of titanium alloy (Ti-6Al-4V), which is one of representative difficult-to-cut materials, with the nanofluid minimum quantity lubrication (nMQL). The miniaturized machine tool system is set up, and then, a series of micro-drilling experiments are performed under compressed air (CA), pure MQL and nMQL for a comparison. For the nanofluid, nanodiamond particles with the sizes of 35 nm and 80 nm are chosen, and the base fluid is vegetable oil. For the micro-drilling process, an uncoated carbide twist drill having the diameter of 300 μm is used for drilling holes in the titanium alloy workpiece. The experimental results show that the nMQL can reduce the drilling torques and thrust forces, but its effect is more obvious at a low feed rate (10 mm/min). In addition, the edge corner radii and hole circularity errors are significantly reduced in the case of small size (35 nm) and high weight concentration (0.4 wt. %) of the nanodiamond particles at the low feed rate. It is also found that the nMQL effectively mitigates chip adhesion of drill tool and burr of drilled holes.

Research of thread rolling on difficult-to-cut material workpieces

In medicine production Ti-6Al-4V Grade 5 alloys are used. One of the most important tasks is to increase the strength of the products and decrease in value. The possibility to roll special thread on Ti-6Al-4V Grade 5 alloy workpiece on 2-roller thread rolling machine has been studied. This is wrought alloy, treatment of which in cold condition causes difficulties due to low plasticity. To obtain Ti-6Al-4V Grade 5 alloy product with thread by rolling is rather difficult. This is due to large axial workpiece displacements resulting from large alloy resistance to cold plastic deformation. The provision of adequate kinematics requires experimental researches and the selection of modes - speed of rolling and pressure on the movable roller. The purpose of the work is to determine the optimal modes for rolling thread on titanium alloy workpiece. It has been stated that, after rolling, the product strength has increased up to 30%. As a result of the work, the unit has been made and recommendations to choose the optimal rolling process modes have been offered.

Optimization the machining parameters by using VIKOR Method during EDM process of Titanium alloy

The objective of this work is to estimate the optimised Electrical discharge machining (EDM) parameters for maximum productivity and minimum surface integrity using combined RSM (Response Surface Methodology) and VIKOR method. The effect of four process parameters; namely Pulse on time (Ton), Peak current (Ip) Duty Cycle (Tau), and Supply Voltage (V) on the responses such as Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) have been considered. Thirty experiments were conducted on Ti-6Al-4V (Titanium alloy) work piece with copper tool using Central Composite Design (CCD).The optimal Condition of experiment were determine using the Pi value obtained from VIKOR method, a multi criteria decision making method which determines the raking list based on the particular measure of closeness to ideal solution. From the analysis it is found that the Ip = 12A, Ton=100μsec, Tau=18%, V=30V provides highest Pi values.so found to better best equilibrium. As per the Computed means of VIKOR index Ip is the most vital parameter followed by Tau, Ton, and V respectively. The result is confirmed by conducting conformation test and found to be comparable with the result. The findings of the study provides the valuable information regarding the regulate the machining parameters, the responses and confirm higher MRR and accuracy of the EDMed products.

Parametric study of ultrasonic-assisted hole sinking micro-EDM of titanium alloy

Making miniature holes of acceptable tolerances in titanium alloys by conventional drilling is difficult due to frequent tool failure because of its poor thermal conductivity, high hardness, and high chemical affinity with cutting tool materials. Micro-electrical discharge machining (micro-EDM) has been found as a suitable method of machining of miniature holes in titanium alloys but it faces some problems such as improper flushing of the debris, arcing, short-circuiting, frequent adhesion of tool electrode with workpiece, and poor machining rate. To overcome all these problems, authors have developed a new ultrasonic-assisted micro-EDM setup and fitted to already available ZNC-EDM machine. The objective of the present work is to study experimentally the effect of gap current (I g), pulse on-time (T on), pulse off-time (T off), and ultrasonic power (U P) on material removal rate (MRR), tool wear rate (TWR), and hole taper (T a) due to ultrasonic-assisted hole sinking micro-EDM (UA-HS-MEDM) in titanium alloy workpiece. Experimental results reveal that introduction of ultrasonic vibration in hole sinking micro-EDM (HS-MEDM) has significant effect on MRR, TWR, and T a. A comparative observation regarding recast layer and circularity of microholes made by HS-MEDM with and without ultrasonic vibration has also been reported.

티타늄 합금의 나노유체 극미량 윤활 밀링 공정 열특성에 관한 수치 해석 연구

This paper presents a numerical study on the thermal characteristics of a milling process of titanium alloy with nanofluid minimum-quantity lubrication (MQL). The computational fluid dynamics (CFD) approach is introduced for establishing the numerical model for the nanofluid MQL milling process, and estimated temperatures for pure MQL and for nanofluid MQL using both hexagonal boron nitride (hBN) and nanodiamond particles are compared with the temperatures measured by thermocouples in the titanium alloy workpiece. The estimated workpiece temperatures are similar to experimental ones, and the model is validated.

Assessment of material removal capability with vibration-assisted wire electrical discharge machining

Titanium alloys are prevalently used in automotive, aerospace and biomedical applications. It is identified as not easy to machine by conventional machining process because of fast tool wear. Hence, for machining of titanium alloy, non-conventional machining processes are generally recommended. In non-conventional machining, vibration assisted Wire Electrical Discharge Machining has shown promising results to improve the machining rate. The present work will focus on machining of titanium alloy workpiece by vibrating the wire in lateral direction with varied frequency of excitation to enhance the material removal rate and to obtain the required kerf width in Wire Electrical Discharge Machining. Experiments were performed on Ti-6Al-4V alloy material during a wire electrical discharging machine operation using zinc coated brass wire and brass wire electrode. Roughness with all those irregularities on machined surface, with varied vibration condition, are measured with contact stylus type surface roughness measuring instrument. Machined kerf size was measured using non-contact optical Co-ordinate Measuring Machine. White layer formed and surface integrity were examined through Scanning Electron Microscope with provision of Energy Dispersive Spectroscopy. The developed vibrating system worked effectively, improved material removal rate and their surface modification has been obtained and reported.

Influence of Cutter Orientations on Cutting Force in Ball End Milling of TC17

In order to improve the ball end milling multi-axis milling titanium alloy workpiece machining method, the influence of cutter orientations on cutting force is studied in this paper by experiment. This paper uses the tool rotation angle and the tool inclination angle to describe the cutter orientations. Analyse the cutting force under different milling posture. The results prove that, when the tool inclination angle is constant, the change of tool rotation angle will cause changes in the value and direction of the cutting force. Though maintain the tool rotation angle, the change of the tool inclination angle will change the cutting speed, thus make the cutting force decrease first then increase.

Comparison of machining performance of hole-sinking micro-EDM without and with ultrasonic vibration on titanium alloy

Titanium alloys are highly demanding in aerospace industries due to its high strength-to-weight ratio and high hot hardness, and termed as difficult-to-machine materials. Creating microholes of high accuracy in these materials is challenging task for manufacturing industries. Conventional twist drills are generally failed in the micromachining of Titanium alloys due to the low thermal conductivity of these alloys. In consideration of all these problems, authors used self-developed hole-sinking micro-EDM (HS-MEDM) setup without and with the assistance of ultrasonic vibration (UV) to create microholes in Titanium alloy (Ti-6Al-4V) workpiece. Comparative study regarding machining performance in terms of material removal rate (MRR), tool wear rate (TWR), hole taper (Ta) and overcut (OC) at different gap current, pulse on-time and pulse off-time has been reported without and with assistance of UV. It was found that HS-MEDM with UV is more advantageous in producing microholes with higher MRR, lower TWR, Ta and OC, and smoother surface.

Comparison of machining performance of hole-sinking micro-EDM without and with ultrasonic vibration on titanium alloy

Titanium alloys are highly demanding in aerospace industries due to its high strength-to-weight ratio and high hot hardness, and termed as difficult-to-machine materials. Creating microholes of high accuracy in these materials is challenging task for manufacturing industries. Conventional twist drills are generally failed in the micromachining of Titanium alloys due to the low thermal conductivity of these alloys. In consideration of all these problems, authors used self-developed hole-sinking micro-EDM (HS-MEDM) setup without and with the assistance of ultrasonic vibration (UV) to create microholes in Titanium alloy (Ti-6Al-4V) workpiece. Comparative study regarding machining performance in terms of material removal rate (MRR), tool wear rate (TWR), hole taper (Ta) and overcut (OC) at different gap current, pulse on-time and pulse off-time has been reported without and with assistance of UV. It was found that HS-MEDM with UV is more advantageous in producing microholes with higher MRR, lower TWR, Ta and OC, and smoother surface.

Machined Surface Quality in Nano Aluminum Mixed Electrical Discharge Machining

The development of implants in biomedical engineering application nowadays requires materials with good mechanical and physical properties. Conventional machining of high strength alloy materials is a challenge. Non-conventional machining processes such as electrical discharge machining (EDM) of high strength material have its limitations. Among the limitations are surface modification, induced corrosion, residual stress and reducing of fatigue performance during the EDM process. Nano aluminum mixed electrical discharge machining (PMEDM) is envisaged able to address some of the above mentioned problems. In this study, PMEDM machining performance on biomedical grade titanium alloy workpiece using nano aluminum powder is assessed to establish its improvement for biomedical application. The characteristics analyzed are surface roughness (Ra) and surface morphology. Process variable machining parameters used are peak current, ON-time (pulse duration), gap voltage and nano aluminum concentration. Results of nano aluminum PMEDM on titanium alloy material show slight improvement in terms of surface roughness (Ra) and surface morphology as compared to conventional EDM. PMEDM results show fewer defects in terms of cracks, craters and voids.

Corrosion resistance of Ti-Ta-Zr coatings in the Boiling Acid Solutions

In this study corrosion resistance of Ti-Ta-Zr coatings fabricated on VT14 titanium alloy workpieces using a high-energy electron beam injected in the atmosphere was investigated. Estimation of corrosion resistance of surface alloyed layers was carried out by the weight-change method. Boiling solution of 65 % nitric acid in water and 5 % of sulfuric acid in water were used as the corrosive environments. Investigation of samples after corrosion tests was carried out using a Carl Zeiss EVO 50 XVP scanning electron microscope.

Modeling and research of temperature distribution in surface layer of titanium alloy workpiece during AEDG and conventional grinding

Titanium and its alloys are widely recognized as the hardly machinable materials, especially due to their relatively high hardness, low thermal conductivity and possible subcritical superplasticity. Then, a thorough control of the machining process parameters shall be maintained. In this paper, we have concentrated on the grinding of the Ti6Al4V titanium alloy using cBN (boron nitride) grinding wheel combined with the AEDG (abrasive electrodischarge grinding) process. The mathematical model we have dealt with has been based mainly on Jaeger model of the heat taking over between sliding bodies with substantial upgrades related to: estimation of the frictional heat generating based on friction forces distribution, spatial, not only planar, shape of the contact area, generated heat partition between different parties of the grinding process, heat transfer in the multilayered environment. The experimental verification of the theoretical predictions has been carried out. Fundamental difficulty in such a research is placing temperature probes sufficiently close to the ground surface with possibly low space devoted for probes due to the temperature field deformation with relation to the real conditions of grinding. The temperature field in the machined workpiece has been investigated using electronic data logging and DSP methods. Obtained results exhibit clearly that distribution of heat generation in the contact zone could be of the relatively complicated shape due to the external cooling and the very specific heat transfer and accumulation in the titanium workpiece surface layer.

Influence of the stress state on the structure and properties of welded steel and alloy structures

The residual stress due to welding in steel and alloy structures is analyzed. The greatest residual stress is produced by cooling of the welded structure. The results of calculations are in satisfactory agreement with the experimental deformation of the structure in welding on a test bench. The tests reveal the direction of the internal stress and permit assessment of the geometry of parts on the basis of a model of the temperature fields in the butt welding of steel and titanium-alloy workpieces. A coercimeter may be used to assess the stress state of the material and its defect content. By that means, it is possible to predict the structural state and properties of weld joints. The dynamics of welding deformation may be understood on the basis of the internal residual stress and the structural transformations produced by the welding process.

Mathematical simulation and optimization of cutting modes in turning of titanium alloy workpieces

A predictive modeling technique of optimal cutting modes in machining of workpieces made of titanium alloys, different from the well-known ones, is offered. The influence of various factors on the process of cutting for the purpose of defining optimal parameters of machining in accordance with certain effectiveness criteria is examined in the present paper. Mathematical models of optimization, algorithms and computer programmes, visual graphical forms presenting dependences of effectiveness criteria on the master schedule parameters have been worked out. Verification of mathematical models in laboratory and working conditions has been carried out.

An approach for using iterative learning for controlling the jet penetration depth in abrasive waterjet milling

This paper presents a new methodology for controlling the jet penetration in abrasive waterjet milling. The generation of milled parts by means of abrasive waterjet is traditionally done by trial and error, relying mainly on the operator's expertise. An Iterative Learning Control (ILC) based approach is proposed to improve the prediction and correction of depth of the generated jet footprints in a systematic way every time the same part is milled. This approach utilizes a P-type (proportional) ILC algorithm to control the milling process, and uses a geometrical model based on non-linear partial differential equations for predictions of footprints to provide a fast convergence to the process input and reducing errors. The experimental validations of this approach were carried out using a Titanium alloy (Ti6Al4V) workpiece where a slope-varying profile was generated using 220 mesh grit-size abrasives with 0.04kg/min mass flow rate and 1380bar pressure. The results show that the achieved depth accuracy is indeed improved by more than 50% after four iterations when using this approach; providing basis for generating precision freeform surfaces using abrasive waterjet machines in a controlled manner.