Multi-criteria decision making approach for selecting the best Ti alloy turning parameters by analysing the influence of cutting force on surface finish under different conditions

Powder bed methods of additive manufacturing (AM) use either an electron beam (Electron Beam Melting – EBM) or a laser (Selective Beam Melting – SLM) to sequentially melt powder, layer by layer, to build up a 3-dimensional object directly from a powder bed according to a computer aided design (CAD) file. Complexity is free with AM processes, so parts such as the impeller shown in the Figure Left, are natural candidates for AM. With EBM. there are four steps to build each layer in a build. First, the beam is scanned to preheat the powder bed without melting, second, the contours (outer edge) of the area to be melted is traced and powder melted, third, the hatch (area within the contours) is melted and finally any supports that need to be built to support higher layers of the part being built are added. The side face of a part adjacent to powder after an EBM build is shown in the Figure Right. With SLM, a similar strategy is used although powder bed preheating is not necessary (the powder bed remains at ambient temperature or is preheated to a low temperature – up to 200°C – with separate heaters). The result of this low temperature processing is that residual stresses are created. The supports which are added to the model to support higher level downward facing surfaces are structural in nature and used to prevent distortion (unlike those supports in the EBM process which are added for thermal management). The major concerns for incorporation of AM into structural parts are (1) microstructural anisotropy/inhomogeneity, (2) porosity – open near the surface and closed internally and (3) surface finish that is strongly dependent on the orientation of the surface relative to the build direction. Improving the surface finish is critical for certain applications. While finish machining can be used where surfaces are accessible, one benefit of the complexity of part shape is the possibility of building parts with internal channels, inaccessible to machining. Therefore, this paper will discuss recent developments toward the demonstration of electrochemical processing conditions and tooling that enable electrochemical finishing of complex components like shrouded impellers. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes or the addition of chemical species (like HF) to remove the passive film associated with electropolishing of passive and strongly passive materials like Ti alloys. This paper will focuses on pulse/pulse reverse electrofinishing processes developed by Faraday Technology and the technique to scale this approach to functional parts of interest. Acknowledgements: The financial support of USAF Contract No. FA8814-15-C-0007 is acknowledged. Figure 1

NiTi and Ti alloys have been widely used in many applications that demand high specific strength property. However, the wear resistance of these alloys is poor. Various surface coating methods can be applied to enhance the wear resistance. Techniques to produce a nitrided surface such as PVD and CVD have been applied but these techniques have limitations such as poor interfacial adhesion and high temperature distortion, respectively. Laser gas nitriding has been widely studied but its application is still not accepted by the industry. The major problem of laser gas nitriding is that the process involves surface melting which would increase the surface roughness of surface finished components. This paper will report the results achieved by laser gas nitriding without the surface being melted. Laser processing parameters were optimized so that the surface could be nitrided without surface melting and thus the surface finish of the component could be maintained. The microstructure of the nitride surface was studied and X-ray analysis was carried out to examine the nitride structure. Hardness was measured by nanoindentation. The wear resistance of the surfaces with difference grid sizes of nitride tracks was studied. Significant improvement in wear resistance was observed. The process can be used to surface-harden Ti components with finished surface.NiTi and Ti alloys have been widely used in many applications that demand high specific strength property. However, the wear resistance of these alloys is poor. Various surface coating methods can be applied to enhance the wear resistance. Techniques to produce a nitrided surface such as PVD and CVD have been applied but these techniques have limitations such as poor interfacial adhesion and high temperature distortion, respectively. Laser gas nitriding has been widely studied but its application is still not accepted by the industry. The major problem of laser gas nitriding is that the process involves surface melting which would increase the surface roughness of surface finished components. This paper will report the results achieved by laser gas nitriding without the surface being melted. Laser processing parameters were optimized so that the surface could be nitrided without surface melting and thus the surface finish of the component could be maintained. The microstructure of the nitride surface was ...

Powder bed methods of additive manufacturing (AM) use either an electron beam (Electron Beam Melting – EBM) or a laser (Selective Beam Melting – SLM) to sequentially melt powder, layer by layer, to build up a 3-dimensional object directly from a powder bed according to a computer aided design (CAD) file. Complexity is free with AM processes, so parts such as the impeller shown in Fig. 1, are natural candidates for AM. With EBM. there are four steps to build each layer in a build. First, the beam is scanned to preheat the powder bed without melting, second, the contours (outer edge) of the area to be melted is traced and powder melted, third, the hatch (area within the contours) is melted and finally any supports that need to be built to support higher layers of the part being built are added. The side face of a part adjacent to powder after an EBM build is shown in Fig. 2. With SLM, a similar strategy is used although powder bed preheating is not necessary (the powder bed remains at ambient temperature or is preheated to a low temperature – up to 200°C – with separate heaters). The result of this low temperature processing is that residual stresses are created. The supports which are added to the model to support higher level downward facing surfaces are structural in nature and used to prevent distortion (unlike those supports in the EBM process which are added for thermal management). The major concerns for incorporation of AM into structural parts are (1) microstructural anisotropy/inhomogeneity, (2) porosity – open near the surface and closed internally and (3) surface finish that is strongly dependent on the orientation of the surface relative to the build direction. Improving the surface finish is critical for certain applications. While finish machining can be used where surfaces are accessible, one benefit of the complexity of part shape is the possibility of building parts with internal channels, inaccessible to machining. Therefore, this paper will discuss recent developments toward the demonstration of electrochemical processing conditions and tooling that enable a wide range of complex components to be finished, deburred, radiused, or polished. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes or the addition of chemical species (like HF) to remove the passive film associated with electropolishing of passive and strongly passive materials like Ti alloys. This paper will focuses on pulse/pulse reverse electrofinishing processes developed by Faraday Technology of various material groups including but not limited to titanium alloys, tantalum alloys, nickel alloys, stainless steels, niobium, and molybdenum alloys. In particular, this talk will discuss techniques in electrofinishing AM / HIPped parts and the design of tooling that enables complex components / passages to be finished to meet the required specifications. Acknowledgements: The financial support of USAF Contract No. FA8814-15-C-0007 is acknowledged. Figure 1

Powder bed methods of additive manufacturing (AM) use either an electron beam (Electron Beam Melting – EBM) or a laser (Selective Beam Melting – SLM) to sequentially melt powder, layer by layer, to build up a 3-dimensional object directly from a powder bed according to a computer aided design (CAD) file. Complexity is free with AM processes, so parts such as the impeller shown in Fig. 1, are natural candidates for AM. With EBM. there are four steps to build each layer in a build. First, the beam is scanned to preheat the powder bed without melting, second, the contours (outer edge) of the area to be melted is traced and powder melted, third, the hatch (area within the contours) is melted and finally any supports that need to be built to support higher layers of the part being built are added. The side face of a part adjacent to powder after an EBM build is shown in Fig. 2. With SLM, a similar strategy is used although powder bed preheating is not necessary (the powder bed remains at ambient temperature or is preheated to a low temperature – up to 200°C – with separate heaters). The result of this low temperature processing is that residual stresses are created. The supports which are added to the model to support higher level downward facing surfaces are structural in nature and used to prevent distortion (unlike those supports in the EBM process which are added for thermal management). The major concerns for incorporation of AM into structural parts are (1) microstructural anisotropy/inhomogeneity, (2) porosity – open near the surface and closed internally and (3) surface finish that is strongly dependent on the orientation of the surface relative to the build direction. Improving the surface finish is critical for certain applications. While finish machining can be used where surfaces are accessible, one benefit of the complexity of part shape is the possibility of building parts with internal channels, inaccessible to machining. Therefore, this paper will discuss recent developments toward the demonstration of electrochemical processing conditions and tooling that enable a wide range of complex components to be finished, deburred, radiused, or polished. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes or the addition of chemical species (like HF) to remove the passive film associated with electropolishing of passive and strongly passive materials like Ti alloys. This paper will focuses on pulse/pulse reverse electrofinishing processes developed by Faraday Technology of various material groups including but not limited to titanium alloys, tantalum alloys, nickel alloys, stainless steels, niobium, and molybdenum alloys. In particular, this talk will discuss techniques in electrofinishing AM / HIPped parts and the design of tooling that enables complex components / passages to be finished to meet the required specifications. Acknowledgements: The financial support of USAF Contract No. FA8814-15-C-0007 is acknowledged. Figure 1

Powder bed methods of additive manufacturing (AM) use either an electron beam (Electron Beam Melting – EBM) or a laser (Selective Beam Melting – SLM) to sequentially melt powder, layer by layer, to build up a 3-dimensional object directly from a powder bed according to a computer aided design (CAD) file. Complexity is free with AM processes, so parts such as the impeller shown in Fig. 1, are natural candidates for AM. With EBM. there are four steps to build each layer in a build. First, the beam is scanned to preheat the powder bed without melting, second, the contours (outer edge) of the area to be melted is traced and powder melted, third, the hatch (area within the contours) is melted and finally any supports that need to be built to support higher layers of the part being built are added. The side face of a part adjacent to powder after an EBM build is shown in Fig. 2. With SLM, a similar strategy is used although powder bed preheating is not necessary (the powder bed remains at ambient temperature or is preheated to a low temperature – up to 200°C – with separate heaters). The result of this low temperature processing is that residual stresses are created. The supports which are added to the model to support higher level downward facing surfaces are structural in nature and used to prevent distortion (unlike those supports in the EBM process which are added for thermal management). The major concerns for incorporation of AM into structural parts are (1) microstructural anisotropy/inhomogeneity, (2) porosity – open near the surface and closed internally and (3) surface finish that is strongly dependent on the orientation of the surface relative to the build direction. Improving the surface finish is critical for certain applications. While finish machining can be used where surfaces are accessible, one benefit of the complexity of part shape is the possibility of building parts with internal channels, inaccessible to machining. Therefore, this paper will discuss recent developments toward the demonstration of electrochemical processing conditions and tooling that enable a wide range of complex components to be finished, deburred, radiused, or polished. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes or the addition of chemical species (like HF) to remove the passive film associated with electropolishing of passive and strongly passive materials like Ti alloys. This paper will focuses on pulse/pulse reverse electrofinishing processes developed by Faraday Technology of various material groups including but not limited to titanium alloys, tantalum alloys, nickel alloys, stainless steels, niobium, and molybdenum alloys. In particular, this talk will discuss techniques in electrofinishing AM / HIPped parts and the design of tooling that enables complex components / passages to be finished to meet the required specifications. Acknowledgements: The financial support of USAF Contract No. FA8814-15-C-0007 is acknowledged. Figure 1

CNC machining manufacturing is critical to the development of biomedical industries, especially orthopaedic implants. Understanding a material's machinability under different cutting conditions is essential for component design as well as for optimizing the machining process. Despite their widespread use in the biomedical industry, α + β-type titanium (Ti) alloys, such as Ti-6Al-4V and Ti-6Al-7Nb, are being replaced by β or near β-type Ti alloys like Ti-13Nb-13Zr Ti alloy due to issues associated with Vanadium and Aluminium toxicity and lower modulus of elasticity. By simulating the machining of a functional cone of the hip prosthesis femoral component, this work aims to investigate some aspects of the machinability of titanium alloys: Ti-6Al-4V, Ti-6Al-7Nb, and Ti-13Nb-alloy 13Zr. Cutting forces values were registered during the tests. Using correlative microscopy, machined surfaces were examined by measuring roughness and topographic examination. According to the results obtained, the new titanium alloy Ti-13Nb-13Zr alloy presents lower cutting forces and a worse surface finish for a lower feed rate. However, when the feed rate was increased to double the initial value, this alloy had the smallest increase in Ra, compared with the other alloys under test The effect of federate is highly significant in cutting forces and surface finish, with increases in cutting forces of 35%, 45% and 66% on cutting forces for Ti-13Nb-13Zr, Ti-6Al-4V and Ti-6Al-7Nb, respectively.

Titanium alloys are widely used in many fields because of their excellent comprehensive properties. However, its poor friction and wear properties limit its many potential applications. In general, the surface roughness of important parts manufactured by titanium alloy should meet certain requirements. As a low-cost and high-efficiency processing method, barrel finishing has been used for the surface finishing of titanium alloys. The main material removal mechanism of barrel finishing is micro-cutting/grinding, which is similar to the material wear mechanism under some conditions. In addition, titanium alloys are subjected to a low force in common surface finishing processes. Cryogenic treatment is a method that can improve the comprehensive properties of titanium alloys. Therefore, the friction and wear behavior of cryogenically treated Ti-6Al-4V titanium alloy (CT Ti alloy) and non-cryogenically treated Ti-6Al-4V titanium alloy (NT Ti alloy) at a low load and scratch speed was studied comparatively in this paper. The results show that the CT Ti alloy exhibits a lower friction coefficient and wear rate under both dry and wet wear conditions. Under wet conditions, the stabilized friction coefficient is lower than that under dry conditions. The stabilized friction coefficient of CT Ti alloy is 0.18 after reaching a stable wear stage under wet conditions. Under dry wear conditions, the NT Ti alloy mainly showed typical abrasive wear, heavy adhesion wear and oxidation wear characters. The wear mechanisms of CT Ti alloy are mainly abrasive wear, slight adhesion wear and oxidation wear. Under wet wear conditions, the wear mechanism of NT Ti alloy is abrasive wear and slight adhesion wear. After cryogenic treatment, the mechanism for CT Ti alloy is slight abrasive wear.

Cutting tool is a very important element of machining production system. It is primarily responsible for material removal in the form of chips, but also significantly affects multiple machinability characteristics, surface finish, attainable dimensional accuracy, productivity and costs. As for a given machining operation there is a number of alternative cutting tools and inserts from many manufacturers, each characterized by a unique set of characteristics, the selection of a particular cutting tool can be very complex task, yet solvable within the framework of multi-criteria decision making (MCDM) methodology. This study is focused on the development of an MCDM model for selection of the most suitable cutting insert for medium machining of unalloyed structural steel. The model was developed by available information, catalogues of cutting tool manufacturers and machining estimations, and consisted of fourteen alternative cutting inserts from eight well-known cutting tool manufacturers and seven criteria. Initially, the assessment and ranking of alternative cutting inserts was derived by the six multi-criteria decision making (MCDM) methods, however, due to ranking inconsistency, the application of the robust decision making rule was adopted for solving the cutting insert MCDM problem.

The work of manufacturing engineers is to utilize the minimum amount of energy or resources in bringing out a product without compromising on quality. Hence, to achieve this, the engineers must figure out the optimum or the best possible method to fabricate a product. This paper uses a multi criteria decision making (MCDM) model namely Analytical Hierarchical Process (AHP) to determine the best possible machining process to achieve the optimum results for an engraving operation on gear face in an automobile industry which uses five nontraditional machining processes viz; Laser Beam Machining (LBM), Ultrasonic Machining (USM), Electric Discharge Machining (EDM), Electrochemical Machining (ECM) and Electron Beam Machining (EBM). The five criteria considered in this paper are Material Removal Rate (MRR), Surface Finish, Depth Damage, Tolerance and Toxicity. The AHP result shows that ECM is the most suitable machining process as compared to others.

Titanium and Ti alloys are widely used as substitutional materials for natural bone because of their good biocompatibility, high strength, and high corrosion resistance. In our previous studies, TiO2 coating on Ti with Ra (arithmetical means of roughness) < 0.1 μm formed by anodizing had much higher osteoconductivity than that of pure Ti. It can be expected that TiO2 coating with fine surface can improve the osteoconductivity of Ti alloys. In this study, the effects on the osteoconductivity of TiO2 coatings on different kinds of Ti alloys were investigated by in vivo study. TiO2 coatings with Ra < 0.1 μm were formed on 4 kinds of Ti alloys (Ti-6Al-4V (Ti64), Ti-6Al-7Nb (Ti67), Ti-29Nb-13Ta-4.6Zr (TNTZ), Ti-13Cr-1Fe-3Al (TCFA)) using anodizing in H3PO4 aqueous solution. Surface properties of these coatings were evaluated using SEM, XRD, and XPS. In in vivo study, samples were implanted in rats’ tibia for 14 days, and then removed. Cross section of the sample was observed with optical microscope and bone-implant contact ratio (RB-I) at the interface between body tissue and bone was used as a parameter of osteoconductivity. Anatase type TiO2 coatings with Ra < 0.1 μm were uniformly formed on all of the Ti alloys by anodizing at low voltage. These oxide coatings contained the ions of other alloy elements. TiO2 coatings on Ti64 and Ti67 indicated high osteoconductivity similar to that of TiO2 coating on pure Ti. On the contrary, TiO2 coating on TNTZ and TCFA showed low osteoconductivity. It was thought that ions of alloy elements brought bad influence on the osteoconductivity of TiO2.

Non-Traditional Machining (NTM) outperforms traditional processes by offering superior geometric and dimensional accuracy, along with a better surface finish. Photo Chemical Machining (PCM) represents one such NTM process, using chemical etching for material removal. PCM finds substantial application in the creation of microchannels in pharmaceutical, chemical and energy industries. Several input parameters—such as etchant concentration, etching time and etchant temperature—profoundly influence the machining’s quality and efficiency. Therefore, the optimization of these parameters is crucial. This study presents a comparative analysis of five Multiple Criteria Decision Making (MCDM) techniques—Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), Multi-Objective Optimization on the basis of Ratio Analysis (MOORA), Additive Ratio Assessment (ARAS), Weighted aggregated sum product assessment method (WASPAS) and Multi-Attributive Border Approximation Area Comparison Method (MABAC)—for the optimization of the PCM process. Key performance metrics considered are Material Removal Rate (MRR), Surface Roughness (SR), Undercut (Uc) and etch factor (EF). The weights of these criteria were calculated using the Criterion-Induced Aggregation Technique (CRITIC) and was compared with other popular methods like MEREC, Entropy and equal weights. MRR and EF are seen as beneficial criteria, while SR and Uc are perceived as cost criteria. Optimum process parameters were identified as 850 g/L etchant concentration, 40 min etching time and 70°C etchant temperature. Two of the three employed MCDM techniques agreed on these optimal parameters, reinforcing the findings. Furthermore, a strong correlation was observed amongst the employed MCDM techniques, further validating the results.

The outcome of dielectric fluids in electrical discharge machining performance: A review

Nickel-based super alloys, Ti alloys, CFRP, hardened steels, etc., are widely used in aerospace, automobile, chemical, and other industries because of such superior properties as high operating temperature, superior specific strength, outstanding hardness and/or great toughness. These properties, however, also present difficulties in machining, cutting temperature, cutting, adhesiveness, chip controllability and wear. Other distinguishing properties include instable tool life, surface finishing and chip control in machining. This means that the stabilization of cutting is very important, especially when machining NC machine tools. Metal machining involves many parameters, such as cutting tools, cutting oil, cutting speed, feed rate, depth of cut, and machine use. A metal machining engineer therefore must decide all of these parameters to ensure their most suitable values under boundary conditions such as machining time, accuracy and the surface roughness of machined parts. Machining, especially of difficult-to-cut materials, is an optimization problem occurring under specified boundary conditions. Choosing machining parameters, including tool geometry and the most favorable features of work materials, must thus be figured out and optimum cutting conditions selected based both on metal machining theory and on practice. This special issue covers recent development in the machining of difficult-to-cut materials, including hardened steel, stainless steel, titanium alloys, Inconel 718, hard brittle materials and CFRP. All of the papers in this special issue are of great interest and value in machining these materials. We thank the authors for their invaluable submissions and the reviewers for their earnest efforts, without which this special issue would not have been possible.

This study is the first description of the extensive porosity which is preferentially located at the cement-prosthesis interface of cemented femoral components of total hip replacements. The observation is important because the interfacial porosity may decrease the strength of the cement-femoral prosthesis interface and jeopardize the mechanical integrity of the cement mantle. We examined the cement-metal interfaces from a multiplicity of in vivo and in vitro specimens using both optical and scanning electron microscopy. These samples included several stem designs, implants made from either Co-Cr or Ti alloy, implants made with a variety of surface finishes and both centrifuged and uncentrifuged cement. All in vivo and in vitro samples had marked porosity in the cement focally concentrated at the cement-metal interface. The amount of porosity at the interface greatly exceeded the amount of general porosity found throughout the bulk cement. Centrifuging did not affect the interfacial porosity, and neither did alloy nor surface finish. The presence of these pores may be explained by the rheological characteristics of the cement.

This investigation is focused on studying grinding of titanium alloys (Ti-6Al-4V) by using nano Al2O3 grinding wheel as an alternative approach to existing methods of grinding. To evaluate optimum conditions of grinding process output, a full factorial technique has been used. L27 orthogonal array was chosen to arrive at an optimised permutation of grinding depth of cut, speed and feed. Consequently, the optimal combination of parameters was tested and results were compared with those of a conventional grinding wheel. The results show superior surface finish on Ti alloy when ground with nano Al2O3 grinding wheel. Confirmatory tests assured that a great improvement in grey relational grade with fuzzy logic, from 0.551 to 0.749 was observed, which substantiates the progress in the performance at best possible levels of nano grinding parameters. Improvement of 21.47% in surface finish of the ground material using combinations of fuzzy grey relational analysis have been achieved.