Cutting Titanium Alloy Research Articles

An analytical model for predicting the depth of subsurface plastic deformation during cutting titanium alloy

An analytical model for predicting the depth of subsurface plastic deformation during cutting titanium alloy

Comparison of Surface Morphology and Tool Wear in the Machining of Ti-6Al-4V Alloys with Uncoated and TiAlN Tools under Dry, Minimum Quantity Lubrication, Flood Cooling, and Low-Temperature Spray Jet Cooling Conditions.

TiAlN-coated carbide tools have been used to machine Ti-6Al-4V alloys in aviation workshops. However, the effect of TiAlN coating on surface morphology and tool wear in the processing of Ti-6Al-4V alloys under various cooling conditions has not been reported in the public published literature. In our current research, turning experiments of Ti-6Al-4V with uncoated and TiAlN tools under dry, MQL, flood cooling, and cryogenic spray jet cooling conditions were carried out. The machined surface roughness and tool life were selected as the two main quantitative indexes for estimating the effects of TiAlN coating on the cutting performance of Ti-6Al-4V under various cooling conditions. The results showed that TiAlN coating makes it hard to improve the machined surface roughness and tool wear of a cutting titanium alloy at a low speed of 75 m/min compared to that achieved by uncoated tools. The TiAlN tools presented excellent tool life in turning Ti-6Al-4V at a high speed of 150 m/min compared to that achieved by uncoated tools. From the perspective of obtaining finished surface roughness and superior tool life in high-speed turning Ti-6Al-4V, the selection of TiAlN tools is feasible and reasonable under the cryogenic spray jet cooling condition. The dedicative results and conclusions of this research could guide the optimized selection of cutting tools in machining Ti-6Al-4V for the aviation industry.

Finite element asnalysis of Ti1-xAlxN coated tools cutting performance and tool wear during Ti–6Al–4V milling

Ti–6Al–4V alloy, as a typical difficult-to-machine material, is prone to problems such as large cutting forces, high cutting temperatures, and serious tool wear during the cutting process. Ti1-xAlxN coated tools are widely used in machining Ti–6Al–4V alloys. The main wear forms of Ti1-xAlxN coated tools are coating cracking and delamination. After the coating has been delaminated, the tool substrate is in direct contact with the workpiece material, aggravating tool wear and shortening the tool life. Therefore, the milling process of Ti1-xAlxN coated tool cutting Ti–6Al–4V alloy was performed using FEM. The effects of Al contents (Ti0·48Al0·52N, Ti0·38Al0·62N), coating thickness (2, 3, 4 μm), and tool substrate (Cemented Carbide Grade K, M, P) of Ti1-xAlxN coated tools on the cutting performance (cutting force, cutting temperature, maximum principal stress, the temperature and stress of coating-substrate interface) and tool wear were discussed. The influence of the maximum principal stress, the temperature and stress of coating-substrate interface on tool wear were analyzed. This paper can provide a reference for the design and optimization of Ti1-xAlxN coated tools by investigating the wear of Ti1-xAlxN coated tools cutting titanium alloys, which can be used to slow tool wear and prolong tool life.

Finite Element Simulation of Bending Thin-Walled Parts and Optimization of Cutting Parameters

Aiming at the problems of large elastic deformation and low machining accuracy in cutting titanium alloy thin-walled parts, this paper establishes the finite element model of milling titanium alloy thin-walled parts, and simulates and analyses the milling process of titanium alloy thin-walled parts by the statics analysis module of ANSYS 15.0 software. The maximum deformation point of the workpiece in the milling process is determined. Then the combination of cutting parameters that can minimize the deformation is determined by the orthogonal experiments of four factors and four levels. This paper designs the single factor experiments, which study the distribution of the milling force and the deformation law of the parts in the milling process. Moreover, this paper carries out the optimal design of the cutting parameters by orthogonal experiments, which provides a reference for the selection of the cutting parameters for the bending thin-walled parts of titanium alloy.

A novel bionic micro-textured tool with the function of directional cutting-fluid transport for cutting titanium alloy

The need for high-precision titanium alloy components is rising exponentially in the biomedical engineering. However, ultra-precision cutting of titanium alloy is challenging due to the high cutting heat because of its low thermal conductivity, which results in severe tool wear and poor surface finish. Therefore, machining titanium alloys requires excellent cooling and lubricating solution. In this research, inspired by the microstructural surface of the Nepenthes' peristome, a bionic micro-texture (BMT) with the function of directional cutting-fluid transport is developed aiming to improve cooling and lubrication condition in cutting zone. The BMT is designed and fabricated by employing a femtosecond laser on the tool surface after theoretically evaluating the fluid transporting behavior of the BMT and its essential geometry parameters. From the directional fluid transport and ultra-precision cutting tests, it is found that the BMT surface offers a high directional fluid flow rate of 3.7 m/s. Moreover, the BMT tool produces lower cutting force, and generates defect-free morphology and nanoscaled roughness. Furthermore, the BMT tool results in reduced flank wear by 84% and 82% at a cumulative cutting distance of 900 m comparing with the none-texture (NT) and micro-groove-texture (MGT) tools respectively, and exhibits excellent chip adhesion resistance. Therefore, it is feasible and promising to apply the BMT tool in ultra-precision cutting of titanium alloys components.

Multi-Physics Analysis of Machining Ti-6Al-4V Alloy: Experimental Characterization and a New Material Behavior Modeling

Titanium alloys are considered difficult-to-cut materials due to their low machinability. Understanding the physical mechanisms occurring during cutting titanium alloys is of particular interest to improve their machinability. Experimental and numerical investigations on Ti-6Al-4V alloy machining are proposed in this paper. Orthogonal cutting tests are performed. The chip microstructure is characterized using SEM observations coupled with the EBSD technique to reveal the deformation mechanisms occurring inside the microstructure. Based on these microscale observations, a new hybrid flow stress model considering the link between the microstructure and damage evolutions is proposed. The model was implemented FE code to simulate the cutting process. The morphology of generated chips and microstructural parameters were deeply analyzed and compared with experimental data. The effect of the dynamic recrystallization phenomenon and its interaction with damage on the cutting process was discussed. The model can be applied for machining simulations of Ti-6Al-4V and other titanium alloys to better choose adequate cutting conditions.

Inverse Identification of the Ductile Failure Law for Ti6Al4V Based on Orthogonal Cutting Experimental Outcomes

Despite the prevalence of machining, tools and cutting conditions are often chosen based on empirical databases, which are hard to be made, and they are only valid in the range of conditions tested to develop it. Predictive numerical models have thus emerged as a promising approach. To function correctly, they require accurate data related to appropriate material properties (e.g., constitutive models, ductile failure law). Nevertheless, material characterization is usually carried out through thermomechanical tests, under conditions far different from those encountered in machining. In addition, segmented chips observed when cutting titanium alloys make it a challenge to develop an accurate model. At low cutting speeds, chip segmentation is assumed to be due to lack of ductility of the material. In this work, orthogonal cutting tests of Ti6Al4V alloy were carried out, varying the uncut chip thickness from 0.2 to 0.4 mm and the cutting speed from 2.5 to 7.5 m/min. The temperature in the shear zone was measured through infrared measurements with high resolution. It was observed experimentally, and in the FEM, that chip segmentation causes oscillations in the workpiece temperature, chip thickness and cutting forces. Moreover, workpiece temperature and cutting force signals were observed to be in counterphase, which was predicted by the ductile failure model. Oscillation frequency was employed in order to improve the ductile failure law by using inverse simulation, reducing the prediction error of segmentation frequency from more than 100% to an average error lower than 10%.

Modelling and analysis of the effect of nonlinear time-varying contact deformation on flexible precision grinding process

Belt grinding is gradually considered to be an effective method for precision machining those aeronautical parts with weak rigidity and complex surface. However, the characteristic of flexible grinding makes it difficult to precisely control the machining process and hinders its further development. In this paper, a series of detailed numerical studies are conducted to study the effect of complex contact deformation on the flexible precision grinding operation of titanium alloy. The flexible process of belt grinding was simulated numerically, and the spatial trajectory equation of abrasive grains in nonlinear time-varying contact state was obtained. Subsequently, the finite element simulation modelling and analysis of a single abrasive grain cutting titanium alloy workpiece under three different boundary conditions (no contact deformation, sinusoidal transformation contact deformation, nonlinear time-varying contact deformation) were performed. The characteristics of grinding morphology and the variation trends of grinding force obtained by simulation were almost consistent with the results of scratch experiments. On this basis, a series of orthogonal simulation studies were conducted to obtain the optimal processing parameters of belt grinding, in consideration of the changes in the spatial positions of abrasive grains caused by the time-varying contact deformation. The above research provides a theoretical framework for investigating the effect of nonlinear time-varying contact deformation, which is of great significance to reveal the mechanism of belt flexible grinding and expand its application in precision machining of aviation parts.

Multilayer-growth of TiAlN/WS self-lubricating composite coatings with high adhesion and their cutting performance on titanium alloy

Tool coatings with a high coefficient of friction (COF) form a built-up edge between the tool and the piece of work when cutting titanium alloy, creating a high cutting temperature, decreased tool life, and lowing the cutting quality. TiAlN/WS self-lubricating composite coatings with high adhesion were prepared via the multilayer growth of WS with low COF and TiAlN with high wear resistance. The TiAlN/WS coating had high adhesion (135.4 N), low COF (0.261), and unchanged hardness (14 GPa). The low COF and high wear resistance originated from the self-lubricating wear-resistance debris at the micron scale with TiAlN coated with amorphous WS. The coating reduced the adhesive wear. By comparing the machining results of the TiAlN/WS coating with those of the TiAlN coating, the flank wear was 45.9% lower for the same cutting length, the machining speed increased from 41 m/min to 100 m/min, the cutting length was over 200% higher at the same flank wear of 0.3, and the self-lubricating composite coating showed good results under dry cutting conditions. Therefore, this coating provides a method for use in high-speed and environmentally-friendly machines for difficult-to-cut materials.

Application of pre-stressed cutting to aviation alloy: The effect on residual stress and surface roughness

The state of residual stress on the machined surface seriously affects its service performance and service life. Theoretically, pre-stressed technique is an efficient and convenient method to adjust the residual stress during the machining. In this paper, theoretical derivation, numerical simulation, and experiment are combined to study the influence of pre-stress on cutting ring parts. According to the principle of pre-stressed cutting, the elastic mechanics analysis and calculation of the pre-stressed load of ring parts are carried out. The relationship between applied pre-stress and radial deformation of the ring parts is set up. The maximum pre-stress that can be loaded is also deduced. Then, a two-dimensional finite element model (FEM) of pre-stressed cutting titanium alloy is established. Finally, a novel pre-stressed loading device for ring parts is developed to perform pre-stressed cutting experiment. The simulated cutting force, chip morphology, and residual stress are consistent with experimental data, which verify the validity of the FEM. Experimental results demonstrate that with the pre-stress increasing from 0 to 410 MPa, the cutting force does not change significantly. The serrated degree of the serrated chip fluctuates around 0.5. And the residual stress of the machined surface decreases sharply from 207 to −49 MPa. Further, a slight reduction in surface roughness and fewer defects on the surface morphology are observed.

Investigation of the result of plastic deformation from the processing conditions of titanium alloys

The research results of the dependence of the magnitude of plastic deformation on the rate of its flow using the example of processing materials by cutting titanium alloys are given in the paper. The process of plastic deformation in titanium alloys is the most interesting. Chip shrinkage characterizes the flow of plastic deformation. The influence of the feed rate on the shrinkage of the chips during turning of the titanium alloy ВТ6 (Russian State Standard GOST 19807-9) has been experimentally determined.

Numerical analysis of performance of different micro-grooved tools for cutting titanium alloy Ti-6Al-4V

To achieve a better performance, a novel cutting tool has been developed with micro-grooves on its rake face. Such tools have great potential in manufacturing. However, micro-grooves of improper directions and shapes may adversely affect cutting tools. This paper investigates the performance of newly designed cemented carbide (WC/Co) cutting tools with micro-grooves on the rake face in the machining of titanium alloy Ti-6A1-4V using finite element (FEM) simulation. The objectives are to explore the influence of the directions and geometrical shapes of micro-grooves on the performance of cutting tools in dry turning of the titanium alloy and to compare it with conventional cutting tools. Specifically, the following aspects are compared: cutting temperature, cutting force, chip morphology, and stress distribution. It is found that these micro-grooved cutting tools generate lower cutting force and cutting temperature and increase chip curling. The maximum reduction of cutting force and cutting temperature occurs under different machining parameters. Compared with linear micro-grooves, the curvilinear micro-grooves diffuse the tool stress and weaken the stress concentration on cutting edges. In addition, the secondary cutting phenomenon of micro-grooved tools is analyzed, which can be effectively alleviated by reducing the width of micro-grooves and setting a reasonable radius of the secondary cutting edge.

Performance analysis of double-groove cutter based on ABAQUS numerical simulation

In order to study the influence of double-slotted cutter on chip forming, this paper uses the general finite element simulation software ABAQUS, and builds a finite element model based on Johson-cook material model and Johson-cook fracture criterion. This paper analyzes the changes in cutting force and cutting temperature obtained when cutting titanium alloys with three different double-slot structures. This paper draws the cutting force and cutting temperature change curve at the tool tip, and analyzes and compares the post-processing results of the three geometries. The test results show that the double concave arc groove cutter has less cutting force and cutting temperature during cutting, and the cutting process is relatively stable, which is more suitable for cutting than other groove types.

Thermal Behavior of Single-Crystal Diamonds Catalyzed by Titanium Alloy at Elevated Temperature

Single-crystal diamonds are considered as the best tool material for ultra-precision machining. However, due to its low thermal conductivity, small elastic modulus and strong chemical activity, titanium alloy has poor machinability and is a typically difficult-to-machine material. Excessive tool wear prevents diamonds from cutting titanium alloy. This study conducts a series of thermal analytic experiments under conditions of different gas atmospheres in order to research the details of thermochemical wear of diamonds catalyzed by titanium alloy at elevated temperatures. Raman scattering analysis was performed to identify the transformation of the diamond crystal structure. The change in chemical composition of the work material was detected be means of energy dispersive X-ray analysis. X-ray photoelectron spectroscopy was used to confirm the resultant interfacial thermochemical reactions. The results of the study reveal the diffusion law of the single-crystal diamond under the action of titanium in the argon and air environment. From the experimental results, the product of the chemical reaction corresponding to the interface between the diamond and the titanium alloy sheet could be found. The research results provide a theoretical basis for elucidating the wear mechanism of diamond tools in the titanium alloy cutting process and for exploring the measures to suppress tool wear.

Study of the effect of sharpness of cutting tools on the formation of defects in the surface finish in micro cutting titanium alloys

The quality of machining of titanium alloys in the aviation and medical fields, characterized by the presence of micro vias, scales and surfacing on the treated surface, as well as the level of roughness is important in the manufacture of key parts. The quality parameters of the treated surface are influenced by many factors - cutting modes (cutting speed, depth and feed), cutting tool parameters (geometry of the cutting part, hardening coating, sharpness of the cutting wedge, etc.), technological equipment parameters (rigidity and accuracy), etc. The aim of the work was investigation of treated surface of titanium alloy VT1-00 when milling with small thicknesses of the shear layer, commensurate with the sharpness of the cutting wedge of the cutter. Method. The method of investigation of the treated surface during milling of titanium alloy on the micro level with the use of standard and high-quality carbide cutting tools is proposed. Results. Operating experience of the received carbide tool has shown that sharpness of a cutting wedge influences quality of the processed surface characterized by microwaves, scales and burrs, also by the roughness of the treated surface. On the basis of carried out researches it is established that for maintenance of conditions of normal cutting and chip formation it is necessary to provide sharpness of the cutting wedge characterized by the conditional entered radius of a blade rounding having values less than values of the sizes of grains of a processed material, that is re < 5 μm. Field of application. The obtained results of work allow to substantiate the recommendations on the required sharpness of carbide cutting tools used for milling of titanium alloys at the micro level. Conclusions. Experiments on the study of the process of cutting of titanium alloy VT1-00 at the micro level to determine the effect of cutting tool sharpness on the quality of the treated surface (microwaves, scales and burrs), allow to form recommendations on its initial state and determine performance.

Investigation on surface quality of high-speed cutting titanium alloy Ti6Al4V based on Split-Hopkinson pressure bar

High-speed cutting technology has the characteristics of high material removal rate and excellent processing quality. To investigate the surface quality of high-speed cutting Ti6Al4V alloy, the orthogonal cutting experiment is the cutting device based on improved Split-Hopkinson pressure bar carried out with a cutting speed of about 7–16 m/s. Surface roughness, residual stress and three-dimensional surface topography are examined to characterize the surface quality. And the chip geometry parameters are measured to analyze the formation mechanism of surface topography. The result shows that cutting force and surface roughness increase rapidly with the increase in depth of cut. In the meantime, the periodic microwaves appeared on the machined surface, and their amplitudes increase with the increase in depth of cut. However, surface roughness, residual stress and microwave amplitude all decrease with the increase in cutting speed. Moreover, it is found that the evolution trend of chip thickness and surface roughness with cutting parameters is very similar. Therefore, it can be inferred that there is a strong relationship between surface topography and chip morphology.

Cutting performance of micro-textured WC/Co tools in the dry cutting of Ti-6Al-4V alloy

To further improve the cutting performance of WC/Co tools in the dry cutting of Ti-6Al-4V alloy. Experiments in dry cutting titanium alloy were carried out using micro-textured YG8 tools under different cutting speeds and depths. Three kinds of YG8 tools with the rake face machined with line groove, sinusoidal groove, and rhombic groove were adopted as the micro-texture YG8 tools. The cutting force, friction coefficient of the tool-chip contact zone, chip morphology, tool wear, and surface quality of machined titanium alloy were analyzed. The results show that the micro-textured tools can effectively reduce the wear area on the rake face and flank face, improve the wear form on the rake face, reduce the occurrence of oxidation wear, and improve the surface quality of machined Ti-6Al-4V alloy. Therefore, micro-textured tools can effectively improve cutting performance and prolong tool life. The existence of micro-texture on the tool surface has a certain influence on the tool performance. The line groove-textured tool has the best effect, followed by the sinusoidal and rhombic groove-textured tools.

Performance of CrCN-WS2 hard/soft composite coated tools in dry cutting of titanium alloys

In this work, a CrCN-WS2 hard/soft composite coating was deposited on the surface of cemented carbide cutting tools to improve the cutting performance of the tool during dry cutting titanium alloys. To analyse the improvement, the cutting performance of CrCN-WS2 hard/soft composite coated tool (CWT) was compared to that of traditional uncoated tool (NT), CrCN hard-coated tool (CT) and WS2 soft-coated tool (WT) at different cutting speeds. The results show that among the four cutting tools, CWT exhibited the best cutting performance. Compared to those of NT, the main cutting force Fz of CWT decreased by 21.8 %–45.4 %, the radial thrust force Fy decreased by 8.2 %–34.0 %, the adhesion height of CWT decreased by 31.0 % and the cutting temperature of CWT decreased by 6.7 %–34.8 %. It was also shown that CWT is more suitable for high-speed cutting of TC4 titanium alloy.

Effects of high-pressure coolant on cutting performance of high-speed ultrasonic vibration cutting titanium alloy

As a novel machining process, high-speed ultrasonic vibration cutting (HUVC) has been successfully applied for high-speed machining of titanium alloys recently. To sufficiently exploit its cutting advantage over conventional cutting (CC), advanced cooling method should be employed in HUVC. In this research, high-pressure coolant (HPC) was firstly introduced to HUVC process and its influences on cutting performance of HUVC titanium alloy were studied, including tool life and wear mechanism, surface quality, cutting temperature and cutting force. The results showed that when cutting speed is 400 m/min, the tool life in HUVC can reach 7.3 times of that in CC if HPC of 200 bar was applied. Besides, the machined surface quality in a successive cutting process in HUVC was significantly improved by applying HPC. In addition, the temperature in HUVC can be reduced for 55 % at 300 m/min compared to CC. Furthermore, the analysis of wear mechanism showed that HUVC with HPC can successfully suppress the occurrence of adhesion wear.

Cutting force and tool wear in cutting Ti-6Al-4V using microstructure-based PCD turning tools

Titanium and its alloys have been widely applied in surgical, aerospace, and medicine because of its high corrosion resistance, strength, heat resistance, and high compatibility with composite structures. However, due to the small cutting deformation coefficient and severe cold hardening phenomenon of titanium alloy, high stress and temperature can easily occur near the cutting edge during machining, which caused chips to adhere to the surface of tools and accelerated tool wear. In order to reduce cutting force and tool wear, researchers have attempted to fabricate microstructures on the tool by grinding, lithography, etching, and other technologies to improve lubrication condition between tools and chips. However, these processes were limited to certain conditions. In this paper, three-dimensional (3D) laminated microelectrodes were used to fabricate various microstructures on polycrystalline diamond (PCD) turning tools by micro-electrical discharge machining (micro-EDM). Moreover, microstructure-based PCD turning tools were used to perform cutting experiments on titanium alloy. During this process, the cutting force of PCD turning tools were measured by force measuring device, and chips were collected and observed. After that, the friction coefficient and tool wear of PCD tools with different microstructures were measured. The experimental results show that microstructures on the rake face of PCD turning tools can effectively reduce friction coefficient for cutting titanium alloy, thus reducing cutting force and tool wear. The type and size of microstructures also affect cutting force and tool wear: the smaller size of microstructure, the smaller values of cutting force and tool wear.