Ultrasonic treatment with nickel electroplating combined with oxidation for developing γ-Al2O3 washcoat on Fe-Cr-Al substrate

Fe-Cr-Al is used as metallic support for catalytic converter due to its high thermal conductivity, lower heat capacity, high temperature and mechanical shock resistance. γ-Al2O3 is the most widely used material as washcoat which embedded on metallic support for the catalytic converter application. The problem is the coating adhesion between the metallic support and the ceramic washcoat becomes a problem in long�term high temperature oxidation. On the other hand, the gamma phase of alumina will be transformed to alpha phase at high temperature. The ultrasonic technique via cavitation bubbles and high velocity can make surface deformation and also accelerate the γ-Al2O3 powders to bombardment occurred on the Fe-Cr-Al surface. This process generates sufficiently heat and γ-Al2O3 layer can be formed on the Fe�Cr-Al surface. Subsequently, electroplating process embeds the nickel and also can strengthen the adhesion when oxidized. Therefore, this work presents the ultrasonic treatment with nickel electroplating for developing γ-Al2O3 washcoat on Fe-Cr-Al substrate and oxidation treatment for catalytic converter application. Washcoat layer on Fe-Cr-Al was prepared by using γ-Al2O3 powders through ultrasonic treatment. Catalyst material was prepared by using nickel electroplating. The oxidation kinetics was conducted at temperatures of 500, 700, 900 and 1100 oC in air for 100 hours. The surface morphology, cross section analysis, chemical composition, elemental maps and phase structure of coated Fe-Cr-Al were analyzed by Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) respectively. The results showed that the surface of Fe-Cr-Al contained γ-Al2O3 powders after ultrasonic treatment. The layer of alumina oxide has been formed on coated Fe-Cr-Al and no spallation occurred after oxidation. It is prove that γ-Al2O3 washcoat and NiO as a catalyst have successfully embedded on Fe-Cr-Al substrate by ultrasonic treatment combined with nickel electroplating at long term high temperature oxidation that enhance the adhesive properly

Investigation of the effect of tool materials and process parameters on dry drilling of Ti-6Al-4V Alloy

The performance of un-coated and TiAlN-coated carbide tools were investigated when dry drilling Ti-6Al-4V alloy. The investigation had been performed in order to find the best tool material performance when dry drilling Ti-6Al-4V. The effect of spindle speed and feed rate on thrust force, torque, dimensional tolerance, and surface roughness were reported. Response surface methodology (RSM) based on central composite design (CCD) is used to perform the investigation. In addition, RSM based on CCD integrated with desirability function is used to determine the optimum input conditions that produce the most desirable quality characteristics (minimum tolerance and surface roughness) with good productivity. Analysis of variance (ANOVA) is used to detect the relative significance of the input factors on each response

Comparative study between wear of uncoated and TiAlN-coated carbide tools in milling of Ti6Al4V

As is recognized widely, tool wear is a major problem in the machining of difficult-to-cut titanium alloys. Therefore, it is of significant interest and importance to understand and determine quantitatively and qualitatively tool wear evolution and the underlying wear mechanisms. The main aim of this paper is to investigate and analyse wear, wear mechanisms and surface and chip generation of uncoated and TiAlN-coated carbide tools in a dry milling of Ti6Al4V alloys. The quantitative flank wear and roughness were measured and recorded. Optical and scanning electron microscopy (SEM) observations of the tool cutting edge, machined surface and chips were conducted. The results show that the TiAlN-coated tool exhibits an approximately 44% longer tool life than the uncoated tool at a cutting distance of 16 m. A more regular progressive abrasion between the flank face of the tool and the workpiece is found to be the underlying wear mechanism. The TiAlN-coated tool generates a smooth machined surface with 31% lower roughness than the uncoated tool. As is expected, both tools generate serrated chips. However, the burnt chips with blue color are noticed for the uncoated tool as the cutting continues further. The results are shown to be consistent with observation of other researchers, and further imply that coated tools with appropriate combinations of cutting parameters would be able to increase the tool life in cutting of titanium alloys

Master of Science

thesisSurface integrity plays a very important role in the life and functionality of machined surfaces used in a variety of engineering applications. Manufacturing processes and their sequence, along with the selection of cutting conditions and cutting tools, eventually dictate the type of surface that is being produced. Surface integrity is subdivided into several components, of which, some important components are surface roughness, residual stresses and subsurface microstructures. Enhanced understanding of all these factors and their interactions will potentially lead to advanced knowledge driven machining process planning. This thesis focuses on an experimental investigation of the effects of cutting tool coatings and cutting fluid application on surface integrity (residual stress, surface roughness and subsurface microstructure) in machined Ti6Al4V titanium alloy. For measuring residual stresses, the hole drilling method was used in this thesis research. The tools selected for the machining were uncoated flat-faced, uncoated grooved, multilayered (TiCN/Al2O3/TiN) CVD coated grooved, and single-layered (TiAlN) PVD coated grooved tools with tungsten carbide substrates. Three different cutting fluid application conditions were used namely: dry, minimal quantity lubrication (MQL) and flood. To illustrate the significance of this thesis, it was observed that a grooved multilayered CVD coated cutting tool under the influence of MQL condition, induced the highest near-surface residual stresses; on the other hand, the same tool, when machined under dry condition, produced the lowest residual stresses. Thus, it can be seen that a specific cutting tool material and/or geometry produce significantly different surface integrity when it is combined with different cutting fluid application conditions. Moreover, the microstructural analysis performed on these machined workpieces revealed significant changes in the subsurface microstructure with respect to the type of cutting tool-cutting fluid application combination used and correlated strongly with the measured residual stress profiles. The combined effect of the type of cutting tool along with the type of cutting fluid application condition on surface integrity is extremely significant. The results and findings o f this thesis have the potential to aid in choosing the combination of the cutting tool and the cutting fluid application that are best suited for machining. Apart from that, this thesis also provides several recommendations for future research on the fundamentals of the interactions between machining parameters such as tool coatings, tool geometry and cutting fluid applications and their significant effects on the generated surface integrity and the life of the component there after

Comparative Analysis of the Machinability of Various Titanium Alloys

Titanium alloys have a good strength to weight ratio, amazing corrosion resistance. These alloys are mostly used in the aerospace, biomedical and automotive industries. However, titanium alloys are difficult to machine since they are chemically reactive and have low thermal conductivity. Drilling is an important machining process with titanium alloys since it is used is most titanium applications. The machinability of titanium alloys varies depending on the method the titanium alloy was manufactured. There is a lack of knowledge for drilling additive manufactured titanium and powdered metallurgy titanium. This study will investigate and compare the wear of various drill bits with various manufactured titanium alloys using a constant feed rate and cutting speed. The titanium alloys used include the reference alloy of Ti-6Al-4V, powder metallurgy titanium and additive manufactured titanium. The drill bits used include high speed steel drill bits, three flute carbide drill bits and coated carbide drill bits. Additionally, the torque is recorded to analyze the drilling performance for each experiment. The drill bit tips, the drilled holes, and the drilled in the workpiece, and the drilled chips were studied microscopically to determine the wear rate of the drill bits, the material transfer, the quality of the drilled surfaces, and the ease of chip dejection. The additive manufactured titanium showed promising material properties but the machinability aspect showed that the wear was poor compared to the reference Ti-6Al-4V alloy

Master of Science

thesisA fundamental understanding of machining-induced microstructural alterations and their correlation with topographical (surface roughness) and mechanical (microhardness and residual stresses) characteristics of surface integrity will aid in improved process planning for obtaining a desired surface quality. The final machined surface quality will govern the component's performance by influencing fatigue life, creep resistance, stress corrosion, and so forth. The selection of cutting conditions, cutting fluids, and cutting tools will eventually dictate the type of surface that is being produced in machining. The selection of these conditions is possible only by investigating and understanding their effects on the eventual state of the machined surface from both metallurgical and mechanical stand points. Hence, a multiscale surface integrity approach (macro, micro and submicro scale) has been adopted in this thesis to study the effects of cutting conditions, cutting tools, and varying cutting fluid applications on the final surface state. The major aim of this thesis is to establish a fundamental understanding among topographical, mechanical, and microstructural characteristics of machining-induced surface integrity in Ti-6Al-4V titanium alloy. Additionally, this thesis also investigates the performance of Targeted Minimum Quantity Fluid (TMQF) application which strategically targets the cutting fluid (300ml/h) on the rake and flank face of the cutting tool while machining. Two inherently different cutting fluids (vegetable oil and synthetic fluid) were tested with TMQF application. The results obtained from TMQF machining are subsequently compared to those from dry and conventional flood machining (6 l/min) for further evaluation. Two different cutting tools (an uncoated tungsten carbide tool and a PVD-coated tungsten carbide cutting tool) were used to evaluate their interaction with cutting fluid application as well as their effects on the final machined surface state. The microstructural characterization of the machined surfaces showed the presence of higher concentration of low angle grain boundaries (less than 5°) at the near machined surface for all cutting tool and cutting fluid applications under investigation. However, machining under the dry condition yielded a higher concentration of low angle grain boundaries at a larger depth (∼100μm) from the machined surface compared to the other three cutting fluid applications. The presence of low angle grain boundaries is an implication of severe plastic deformation. Furthermore, machining under the dry condition produced a tensile residual stress profile and a lower hardness profile unlike those obtained with the other three cutting fluid conditions. These results clearly indicate the correlation between microstructural and mechanical characteristics of machining-induced surface integrity. Flood machining with an uncoated tool and a PVD-coated tool produced contrasting residual stress profiles that signify the effect of the interactions between the cutting tool material and the cutting fluid application on the final surface state. Also, significantly different residual stress profiles were obtained for TMQF machining and flood machining which underline the importance of selecting the right cutting fluid application. The results from this thesis have the potential to close the knowledge gap between microstructural and mechanical characteristics of machining-induced surface integrity. Additionally, this thesis can aid in choosing the right combination of cutting fluid application and cutting tool for finish machining operation of Ti-6Al-4V titanium alloy to obtain a desired final superior surface integrity

A study of the effect of conventional drilling and helical milling in surface quality in titanium Ti-6Al-4V and Ti-6AL-7Nb alloys for medical applications

In the manufacturing of a medical device, may occur the need to make a hole with a specific function. Among current methods, conventional drilling (CD) referred in this work as drilling (D) and helical milling (HM) are two options with different potential. When making the hole, it is important to choose the most suitable method to obtain the desired geometry and ensure the functionality of the device. This work aims to analyze surface parameters as, arithmetic average height (R a ), the maximum height of the profile (R t ), the average peak to valley height (R z DIN), chip formation and the geometric deviation of holes obtained by the previously referred manufacturing processes. The specimens, with cylindrical geometry, were made of titanium alloys, Ti- 6Al-4V and Ti-6Al-7Nb, currently used in the manufacture of medical devices. For this purpose, holes were made in a machining centre with different feed rate (F) for both methods and in the value of vertical step (a p ) in HM. The results obtained demonstrate that, at lower F and a p , HM presents better results. The Ti-6Al-7Nb alloy presents better roughness results compared to Ti-6Al-4V, validating it as a material able to be used in medical devices according to the fact that, a lower roughness is associated with higher corrosion resistance and fewer fatigue problems derived from it in components. By the work carried out, can be concluded that the roughness values obtained in HM are lower to those obtained by D making HM as a better option in hole making.publishe

Impact of Palm Oil based Minimum Quantity of Lubrication on Machinability of Ti and its Alloy (Ti-6AI-4V)

This project investigates the usage of palm oil as a metal cutting fluid in minimum quantity lubrication assisted turning operations and its effect on surface roughness, tool wear and cutting temperature for Titanium alloy Ti-6Al-4V. Artificial Neural Network models were developed to determine the optimum cutting parameters considering the sustainability of palm oil in titanium alloy machining to improve future manufacturing costs and qualities

Effects of minimum quantity lubrication technique in different machining processes - a comprehensive review

The cooling condition has a significant effect in the metal cutting industry, which has a crucial role in cooling and lubricating the workpiece-tool interface, reducing friction, and removing chips from the cutting area. Almost 15-20% of the overall machining cost was incurred from cooling and lubrication. So, the considerable cost can be occurred due to the supply, preparation, and disposal of cooling lubricants. Moreover, exposure to these substances can pollute the environment and hamper operators' health. Therefore, of late, researchers have been giving priority to investigate the effects of the Minimum Quantity Lubrication (MQL) techniques in machining as it alleviates the coolant usage by splashing fluid and compressed air mixtures. In this lubrication technique, the maximum fluid flow is less than 50ml/h, whereas flooded cooling technology uses up to 12,000 litres per hour. Most researchers found that a lower coefficient of friction, better surface finish, reduced cutting forces, and torques can be obtained using the MQL method in an optimized manner compared to dry and wet machining. Moreover, besides improving machinability characteristics, the MQL technique also complies with green and sustainable machining. Thus, a prospective solution to dry and wet processing. This paper represents the brief discussion and mechanism of the MQL technique and the effects of the MQL technique on the performance parameters of different machining processes