Surface Integrity Of Titanium Alloy Research Articles

Electrical discharge and arc milling with automatic tracking of optimal flushing direction: A novel high-efficiency compound machining method

The arc milling method has the advantages of high machining efficiency and low cost and is independent of the strength and hardness of machined materials. However, frequent electrode back-offs and the risk of workpiece burning may occur if erosion products are not removed promptly. In this study, it was found that the flushing method of the working medium had a significant impact on the machining performance of arc milling. Based on this, a novel high-efficiency compound machining method of electrical discharge and arc milling with automatic tracking of the optimal flushing direction was proposed. An automatic tracking optimizer for external working medium injection was designed to determine the optimal external flushing direction according to the feed direction. The influence of flushing methods, working mediums, and machining parameters on the machining efficiency, tool electrode wear rate, machining error, and surface integrity of titanium alloys were investigated. The results indicated that better machining performance and environmental friendliness were achieved using the compound flushing method of outer compressed air and inner deionized water. Additionally, the automatic tracking flushing method in the opposite direction of the feed direction showed superior results compared to other directions. The material removal rate with the opposite direction injection could be increased up to 1.62 times that of the same direction, and the relative electrode wear rate could be reduced by 14.76%. This novel method has broad application prospects for machining parts with difficult-to-cut materials in aerospace and military industries.

Study on Surface Integrity and Fatigue Properties of TC4 Titanium Alloy by Surface Ultrasonic Rolling.

In this paper, the influence of a surface ultrasonic rolling process on the surface integrity of TC4 titanium alloy and its influence on the fatigue properties were studied. By comparing and analyzing the surface roughness, microhardness, residual stress, microstructure, and fatigue fracture, the surface strengthening and modification mechanism of TC4 titanium alloy is discussed. The results show that the surface roughness of titanium alloy is observably decreased after the suitable surface ultrasonic rolling process, and the maximum Ra value can be reduced to 0.052 μm. The axial residual stress on the specimen surface can be increased to -685 MPa. The hardening rate of the surface hardness of the sample was 35%. The residual compressive stress and hardness of the sample surface increased with the increase of static pressure. However, the increase of feed rate and rational speed was less. After surface ultrasonic rolling, the sample surface exhibited obvious grain refinement, the number of high-angle boundaries increased to include the formation of nano-equiaxed grains. The fatigue strength increased by 52% from 280 MPa to 425 MPa. Under 450 MPa, the fatigue life of samples with SUR 2 was the highest, at about 7.7 times that of the original samples. The surface integrity of titanium alloy samples after surface ultrasonic rolling treatment is greatly improved, which is the reason for the significant increase in fatigue life of the samples.

Wear behavior of alumina abrasive belt and its effect on surface integrity of titanium alloy during conventional and creep-feed grinding

Abrasive belt grinding is commonly used in the surface processing of key components of major equipment, such as blade, blisk and rail, due to its cold and flexible processing characteristics. Creep feed belt grinding (CFBG) can effectively improve the processing efficiency; however, it will result in severe abrasive belts wear and low grinding quality. This study comparatively investigated the abrasive belt wear behavior and its effect on surface integrity of titanium alloy during CFBG and conventional belt grinding (CBG), It was revealed that CFBG led to more severe abrasive belt wear than CBG, and the main wear form of abrasive belt was abrasive grain fracture (account for more than 40%) during CFBG, while that was abrasive grain attrition during CBG. Besides, the grinding temperature and grinding force in CFBG were more significant than those in CBG. With the increase of the abrasive belt wear, the grinding temperature and grinding force gradually decreased. Furthermore, as the abrasive belt worn, the ground surface was gradually flattened, and the roughness of CFBG reduced from 1.16 to 0.50 μm, while that in CBG reduced from 0.704 to 0.560 μm. Compared with CBG, an apparent plastic flow and oxidation of titanium alloy occurred due to the temperature effect during CFBG, and the surface residual stress transformed from compressive to tensile as abrasive belt wore.

Study of Surface Integrity of Titanium Alloy (TC4) by Belt Grinding to Achieve the Same Surface Roughness Range

Titanium alloy materials are used in a variety of engineering applications in the aerospace, aircraft, electronics, and shipbuilding industries, and due to the continuous improvement of the contemporary age, surface integrity needs to be improved for engineering applications. Belt grinding parameters and levels directly affect the surface integrity of titanium alloys (TC4), which further affects the fatigue life of the titanium alloys during service. In order to investigate the surface integrity of titanium alloys at different roughness levels, the surfaces were repeatedly ground with the same type and different models of abrasive belts. The results showed that at roughness Ra levels of 0.4 μm to 0.2 μm, the compressive residual stresses decreased with increasing linear velocity and there were problems with large surface morphological defects. At the roughness Ra of 0.2 μm or less, grinding improves the surface morphology, the compressive residual stress increases with increasing feed rate, and the surface hardness decreases with increasing linear velocity. In addition, the research facilitates the engineering of grinding parameters and levels that affect surface integrity under different roughness conditions, providing a theoretical basis and practical reference.

Thermo-mechanical coupling during belt grinding and corresponding surface integrity of titanium alloy

Thermo-mechanical coupling during belt grinding and corresponding surface integrity of titanium alloy

Enhancing surface integrity of titanium alloy through hybrid surface modification (HSM) treatments

The current study investigates the development of a novel hybrid surface modification (HSM) technique to improve the surface integrity of Ti–6Al–4V alloy. The approach combines the mechanical shot peening (SP) and the deposition by Physical Vapour Deposition (PVD) of a tungsten-doped diamond-like carbon coating (WC/C) on Ti–6Al–4V surfaces. The mechanical shot peening induced high surface roughness increasing the metallurgical bonding sites for the PVD deposition, whereas mainly the grain growth during the deposition, was successfully eliminated. The mechanical SP process induced the high strain lattice misorientations evident for increasing the dislocation density in the crystalline structure. The Electron Backscatter Diffraction (EBSD) results suggest that subjecting the SP specimens to a temperature of 240 °C for more than 3 h during coating deposition, results in a reduction of dislocation densities, presumably as a result of dislocation annihilation by heat-activated dislocation mobilisation. Hence, the presented Grain Orientation Spread maps suggest that some degree of macro and micro stress relaxation may have occurred during the coating deposition treatment. Further, the Raman spectroscopy confirms the existence of beneficial compressive residual stresses on both PVD and hybrid (HY) coated surfaces. Comparatively, the HY surfaces show a high hardness of 12.08 GPa and high elasticity indices (H/E ratios) of 0.1.

Study on surface integrity of titanium alloy machined by electrical discharge-assisted milling

• Electrical discharge-assisted milling (EDAM) can improve the surface integrity of Ti-4Al-6 V. • EDAM can reduce the surface roughness compared with conventional milling (CM). • Compared with CM, the residual tensile stress generated by EDAM is smaller. • The microhardness of machined surface after EDAM is relatively smaller than CM. • Moderate capacitance has more positive influence for surface integrity. Electrical discharge-assisted milling (EDAM) is an efficient machining process for titanium alloys according to previous studies. However, a complete understanding of the surface integrity of titanium alloy machined with EDAM is not yet sufficient. Therefore, in this paper, surface defects such as chip layer adhesion, debris, feed marks, and burrs were investigated and identified. Among them, the adhesion of the chip layer is the most common surface defect and is the factor that has the greatest influence on the surface quality. In addition, surface roughness, micro-hardness, and residual stress were analyzed and discussed. The results show that the surface roughness of EDAM is significantly improved compared to conventional milling (CM). Also, the residual stress generated by EDAM is much smaller than that of CM, and the main type of residual stress is residual compressive stress. Similarly, the surface microhardness after EDAM is also slightly smaller than that of CM. This increased surface integrity is due to the material softening effect due to the heat generated by the discharge spark. Consequently, EDAM is a good candidate method for efficient machining of titanium alloys.

Improvement of Ti–6Al–4V surface integrity through the use of high-speed ultrasonic vibration cutting

High-speed ultrasonic vibration cutting (HUVC) has been demonstrated to be a good machining technique for titanium alloys. However, although surface integrity is known to strongly impact the service performance of components (e.g., wear resistance and fatigue performance), the surface integrity of titanium alloys machined via HUVC has not been investigated. In this study, the effects of HUVC on various aspects of the surface integrity of Ti–6Al–4V were investigated. First, the ironing effect of HUVC was analyzed. Then, an experiment for comparing the HUVC technique to a conventional cutting (CC) technique was carried out under the conditions of a cutting speed range of 100–400 m/min. The specimens subjected to HUVC were found to have lower surface roughness, a more uniform surface texture, a thicker subsurface deformation layer (27–82 µm), and higher surface micro-hardness (413–472 HV0.2) and compressive residual stress (−574 to −925 MPa in the feed direction) than those subjected to CC.

Investigation of Ti-6Al-4V surface integrity from milling process

The applications of titanium alloys vary from aerospace industry, medical device and military, however having many challenges in the machining process due to difficult-to-machine characteristic of the material. This study focused on surface integrity of titanium alloy grade Ti-6Al-4V after milling process with different set of parameters. This research investigates the effect of surface integrity of titanium alloys (Ti-6Al-4V) after milling operation with difference cutting parameters such as feed rate, depth of cut and cutting speed. Characterization and measurements were taken on the surface morphology, residual stress, surface roughness and surface hardness. It was found out that from the experiment, the highest cutting speed at 8000 rpm produced lowest surface roughness value of 2.066 μm, while lowest cutting speed at 4500 rpm produced highest surface roughness of 2.55μm. The residual stress analysis shown that all the surfaces produced compressive stresses of more than 500 MPa. It is also found out no evidence of transformation at the morphology of the machined surface. Microhardness measurement at the depth 10 μm to 500 μm from the machined surface only shows slight increase of hardness, however, at the range from machined surface to 10 μm indicates low hardness due to softening effect from the machining process. This demonstrated that surface integrity of titanium alloys does effect by the machining parameters.

Effect of Vegetable Oil–Based Hybrid Nano-Cutting Fluids on Surface Integrity of Titanium Alloy in Machining Process

Abstract In the present work, an attempt is made to examine the machining performance in turning titanium alloy using vegetable oil–based hybrid nano-cutting fluids. The sesame oil–based hybrid nanofluids with carbon nanotubes (CNT)/molybdenum disulphide (MoS2) in the ratio of 1:2 are used to test the effect of surface integrity in the machining of titanium alloy. The cutting forces, cutting temperatures, surface roughness, and microhardness of the machined surface were measured. The machined surface is analyzed for machining-induced residual stresses and changes in the surface topography. Machining performance improved with vegetable oil–based hybrid nano-cutting fluids in reducing cutting forces and cutting temperatures. The percentage reduction of temperatures in the cutting zone under 0.5, 1, 1.5, and 2 wt. % and conventional cutting fluids (CCFs) are 70.2, 58.2, 63.1, 67.3, and 56.7, respectively, compared with dry machining. The percentage reduction in cutting forces are found to be 39.4, 70.9, 42.7, 73.2, and 72.3 for CCF 0.5, 1, 1.5, and 2 wt. % nanoparticle inclusions (NPI) compared with dry cutting, respectively. The percentage reduction in surface roughness (Ra) under CCF is 9.6, 24.4, 23.2, 22.4, and 26.7 for 0.5, 1, 1.5, and 2 wt. % NPI respectively, compared with dry cutting. The microhardness of the machined surface increased, and residual stresses are encouraging with hybrid nano-cutting fluids.

Effects of Cooling Conditions on Surface Integrity in Turning of TC4 Alloy

Machined induced surface integrity of titanium alloy is of great importance due to its strong correlation with the functional performance and service life. In this paper, the effects of different cooling conditions on the surface integrity of TC4 alloy were studied experimentally. The results showed that the values of surface roughness and surface residual stress under cryogenic condition were lower than those under dry condition and emulsion cooling condition with the same cutting parameters, while the influence of cooling condition on the microhardness of the machined surface is not obvious. Cryogenic cutting is an effective way to machine titanium alloy.

An Investigation of the Influence of a Micro-Textured Ball End Cutter’s Different Parameters on the Surface Residual Stress of a Titanium Alloy Workpiece

When machining titanium alloy parts, aside from accuracy, the other key concern when evaluating their quality is the integrity of the machined surface. Residual stress can have a significant impact upon this. A certain amount of residual stress can help to strengthen the workpiece, but excessive residual stress can lead to its deformation. In this paper, we report on an experimental study of the surface integrity of titanium alloy after milling with a microtextured ball-end cutter. Tests were conducted to assess the residual stresses on the surface of titanium alloy workpieces according to the direction of feed and milling. The impact of different micro-texture parameters was also assessed; namely, the diameter, depth, spacing and distance from the cutting edge of the individual pits. Range analysis, which is an orthogonal test, was used to analyze the results of the experiments and a prediction model of surface residual stress was established for the milling of titanium alloy with micro-textured ball-end cutters. This model can provide theoretical support for the optimization of the parameters involved in future milling processes.

An improved analytical model of cutting temperature in orthogonal cutting of Ti6Al4V

Cutting heat has significant effects on the machined surface integrity of titanium alloys in the aerospace field. Many unwanted problems such as surface burning, work hardening, and tool wear can be induced by high cutting temperatures. Therefore, it is necessary to accurately predict the cutting temperature of titanium alloys. In this paper, an improved analytical model of the cutting temperature in orthogonal cutting of titanium alloys is proposed based on the Komanduri-Hou model and the Huang-Liang model. The temperatures at points in a cutting tool, chip, and workpiece are calculated by using the moving heat source method. The tool relief angle is introduced into the proposed model, and imaginary mirrored heat sources of the shear plane heat source and the frictional heat source are applied to calculate the temperature rise in a semi-infinite medium. The heat partition ratio along the tool-chip interface is determined by the discretization method. For validation purpose, orthogonal cutting of titanium alloy Ti6Al4V is performed on a lathe by using a sharp tool. Experimental results show to be consistent well with those of the proposed model, yielding a relative difference of predicted temperature from 0.49% to 9.00%. The model demonstrates its ability of predicting cutting temperature in orthogonal cutting of Ti6Al4V.

Shark-Skin-Inspired Micro-Riblets Forming Mechanism of TC17 Titanium Alloy With Belt Grinding

Belt grinding could improve the surface integrity of titanium alloys, but it is difficult to achieve breakthroughs in the grinding mechanism due to the lack of grinding mechanism of titanium alloy microriblets structure. The characteristics of micro-riblets structure are discussed, and the belt grinding method for the micro-riblets is proposed based on the structural features. On this basis, the corresponding relationship model between the belt grinding and the surface parameters of the micro-riblets structure is established. The standard experimental platform was built and the belt grinding experiment was completed. The typical structural characteristics based on the method were obtained. The influence of the belt grinding process parameters on the formation of micro-riblets structures was analyzed. The results show that the micro-riblets structure achieved by the belt grinding method is dominated by sawtooth riblets. The width of the trench (s) is between 2.5μm and 8μm, the average value is 4.91μm, the height of the trench (h) is between 3.5μm and 9μm, the average value is 5.91μm, and the angle of the trench (α) is between 28° and 68°, the average is 42.3°. At the same time, it can be seen that increasing the grinding positive pressure (Fn), the feed step (P), and reducing the grinding feed rate (v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ) can increase the sawtooth riblets width (s), the groove height (h), and the trench angle (α) of the micro-riblets structure surface. It can also increase the surface of the micro-riblets structure surface sawtooth riblets b <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , b <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Moreover, the groove ratio h/s and the groove bearing side length ratiob <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> /b <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> have a sinusoidal fluctuation tendency, and the ratio mainly jumps up and down at a fixed value.

The Surface Integrity of Titanium Alloy When Using Micro-Textured Ball-End Milling Cutters.

Processing certain kinds of micro-textures onto the surface of tools can improve their wear resistance, reduce the friction between them and machined surfaces, prolong their service life and improve their processing efficiency. When milling titanium alloy with ball-end milling cutters, the cutting force and the cutting heat causes plastic deformation and a concentration of stress on workpiece surfaces, damaging their surface integrity. In this paper, we report on a test involving the milling of titanium alloy, where a micro-texture was placed onto the front of a ball-end cutter and the surface roughness and work hardening of the machined surface were studied. The orthogonal experiment was designed around changes in the diameter of the micro-texture, its depth, the spacing between individual micro-pits, and its distance from the cutting edge. Data from the experiment was then used to assess the influence changes in the micro-texture parameters had upon the roughness and hardening of the surface. The data was processed and analyzed by using regression analysis and a prediction model for surface roughness and work hardening was established. The reliability of the model was then verified. The contents of this paper provide a theoretical basis for improving the cutting performance and the surface machining quality of cemented carbide tools.

Selection of optimal controllable factors for surface roughness in turning of titanium alloy using eco friendly cutting fluids

Surface finish plays a vital role in service components, to ensure a great reliability of sensitive aeronautical components, surface integrity of titanium alloys should be satisfied. Therefore, it is required to optimize process parameters like cutting speed, feed and depth of cut while machining of titanium components for better surface finish.In this study, the optimization and effect of machining parameters on surface roughness in a turning operation is investigated by using the Taguchi’s robust design methodology. The experimental studies are conducted under varying cutting speeds, feed rates and depths of cut. An orthogonal array, analysis of mean (AOM) and the analysis of variance (ANOVA) are employed to study the performance characteristics in the turning of commercial Ti-6Al-4V alloy using uncoated carbide cutting tool with karanja and rice bran oils are as coolants. The results observed that the feed rate is the most influential factor on the surface roughness for both karanja and rice bran oils. The minimal surface roughness value is observed for karanja oil than that of rice bran oil. The optimum process parameters found for karanja oil at a cutting speed of higher level, feed rate of lower level and depth of cut is of moderate level. Similarly, the optimum process parameters found for rice bran oil at a cutting speed of higher level, feed rate of lower level and depth of cut of higher level.

Influence of thermal mechanical coupling on surface integrity in disc milling grooving of titanium alloy

ABSTRACTDisc milling strategy has been applied in grooving for decades for its capacity to provide huge milling force on the difficult-to-cut material. The processing efficiency of machined components thus can be tremendously improved with the application of disc milling. However, the fundamental research of the mechanisms of disc milling on cutting metal materials, especially on titanium alloys, is lacking in the literature. In this study, the milling force and temperature were inspected in disc milling grooving experiment, and the effect of thermal-mechanical coupling on surface integrity of titanium alloy, including surface roughness, surface topography, surface and subsurface residual stress, microstructure, and microhardness, was analyzed. The results showed that a better surface quality can be obtained at the center of the surfaces compared to the marginal regions on the same machined surface. Residual compressive stress was generated on the machined surface and subsurface and gradually reduced to zero with an increase in depth. The microstructure of lattice tensile deformation was emerged along feed direction, while the phase transition was not produced. A hardened layer was found on the machined surface and subsurface, mostly causing by the mechanical loads and oxidation reaction.

Sensitivity Analysis of the Influence of Milling Parameters on the Surface Residual Stress of Titanium Alloy TC11

In order to improve the surface integrity of titanium alloy, a mathematical model of residual stress in x and y direction is established by three factor and three level orthogonal test method. Based on this model, the influence of milling parameters on residual stress is analyzed by using the sensitivity analysis method. Test and analysis results show that the titanium alloy milling process, the residual stress increases with the increase of milling proecess parameters, but in x and y direction the degree of influence is different; The x direction residual stress on milling parameter sensitivity is higher than that of the residual stress in the y direction. x direction of surface residual stress is the most sensitive to change of the cutting speed and then is to the amount of feed per tooth, least sensitive to the cutting depth, y to the same conclusion.

Experimental study on surface integrity of Ti-6Al-4V in high speed side milling

Aiming at the surface integrity of titanium alloy Ti-6Al-4V in high speed side milling, a series of side milling tests were carried out with uncoated carbide milling cutter at various milling speeds. Surface roughness, residual stress, subsurface microstructure and microhardness variations were investigated. The surface roughness measurement results present that the milling speed from 80 to 120 m/min fails to produce better and more stable roughness values compared with the result obtained from 320 to 380 m/min. The residual stresses in the feed direction and axial depth of cut direction are in similar trends for the two milling speed levels mentioned above. Moreover, the residual stress produced at 320 to 380 m/min is lower and more stable than that at 80 to 120 m/min. The microstructure analysis shows that the volume of β phase in the near surface becomes smaller and the deformation of β phase in the near surface becomes obvious with the increase of the milling speed. Subsurface microhardness variation was observed down to 200 μm below the machined surface at 80 to 120 m/min and down to 160 μm at 320 to 380 m/min. It is concluded that better surface integrity and higher material removal rate can be obtained at 320 to 380 m/min than at 80 to 120 m/min.

Surface Integrity of Titanium Alloy Ti-6Al-4V in Ball end Milling

Abstract With the evolution of machine tools and the emergence of new cutting tools such as cermet, CBN; and in framework of the production of parts with complex geometry, the manufacturers were able to realize more and more parts of complex shape. The multi-axis machining is the main technique for achieving the free form; in fact the multi-axis milling with ball end tools attracts the interest of the aerospace industry and the mussel industry which continues to seek ways to improve the surface quality of finished parts. The titanium alloy is widely used in aerospace industry is the subject of this study in fact, the integrity of the surfaces of parts produced by multi-axis milling is an issue more relevant than ever for the aerospace industry. This paper aims to study the influence of the tool position and the parameters cutting precisely the speed feed V f , the engagement of the tool on the roughness 3 D, micro-hardness and microstructure alteration created in sub-surface during the milling of concave surface of titanium alloy type Ti-6Al-4 V.