SYNTHESIZING AND EVALUATION OF NEW COPPER-TUNGSTEN BASED EDM ELECTRODE FOR MACHINING HARDENED MATERIALS

By using Electrical discharge machining (EDM) it is possible to machine any materials that are difficult to machine by using conventional machining technique as long as it is electrically conductive. The performance of EDM is highly depending on the type of electrode being used, the power supply system, and the dielectric system. Copper-Tungsten electrode is the higher in wear resistance but it is difficult to manufacture due to variation of melting point and zero miscibility of copper (Cu) with Tungsten (W). Thus, new modified Copper-Tungsten electrodes were synthesized taking into consideration the variety of melting point and zero miscibility. Ball milling was used to synthesize the new electrode material and Taguchi method is used to design and analyse the experiment. Material removal rate (MRR) and electrode wear (EW) are the main parameters used for testing the performance between the existing Copper-Tungsten (Cu-W) electrode and the new developed electrode. Machining variables selection show that the gap voltage, peak current and pulse on time are the most important ones that contribute on material removal rate, electrode wear and surface roughness (Ra). Results of milling process indicate a clear change in the thickness of crystalline and d-spacing of the milled powder after five hours milling time. The performance of Cu-WC-Si electrode shows an improvement in MRR by an average of 22.5% when milled for 5 to10 hours. The EW of 10 to 20 hours milled Cu-WC-Si improved by an average of 62 % from that achieved by using Cu-W electrode. The performance of Cu-WC-Ti and Cu-WC-Ti-Si electrode show clear improvement in the electrode wear but at the expense of MRR. It is reduced by an average of 86% for Cu-WC-Ti and by 70.1% compared with that achieved by using Cu-W electrode. Si additive improve TWR of Cu-WC-Si electrode where it shows the lowest TWR (10%) compared with that achieved by Cu-WC-Ti (466%) and Cu-WC-Ti-Si (37%). The contribution of milling variables on the performance of the new developed electrodes shows that milling time is the most important variable

Materials review for improved automotive gas turbine engine

The potential role of superalloys, refractory alloys, and ceramics in the hottest sections of engines operating with turbine inlet temperatures as high as 1370 C is examined. The convential superalloys, directionally solidified eutectics, oxide dispersion strenghened alloys, and tungsten fiber reinforced superalloys are reviewed and compared on the basis of maximum turbine blade temperature capability. Improved high temperature protective coatings and special fabrication techniques for these advanced alloys are discussed. Chromium, columbium, molybdenum, tantalum, and tungsten alloys are also reviewed. Molbdenum alloys are found to be the most suitable for mass produced turbine wheels. Various forms and fabrication processes for silicon nitride, silicon carbide, and SIALON's are investigated for use in highstress and medium stress high temperature environments

Fabrication Technologies of the Sintered Materials Including Materials for Medical and Dental Application

This chapter of the book presents the basis of classical powder metallurgy technologies and discusses powder fabrication, preparation, preliminary moulding, sintering and finish treatment operations. A general description of the materials and products manufactured with the classical powder metallurgy methods is presented. New variants are characterised along with special and hybrid technologies finding their applications in powder metallurgy. Special attention was drawn to microporous titanium and to TiAl6V4 alloy fabricated using hybrid rapid manufacturing technologies with selective laser sintering/selective laser melting (SLS/SLM) used for innovative implant scaffolds in medicine and regenerative dentistry. Laser deposition, thermal spraying and detonation spraying of powders are also discussed as special methods in which powders of metals and other materials are used as raw materials

Investigation of pressing and ejection performance of friction-reducing powder-compaction tool coatings

Pressing in dies followed by sintering is the most commonly used process for shaping metal powders into components. The mechanical properties (e.g. tensile and fatigue strength) of the final sintered component depend on the green-compact properties resulting from the compaction process. Apart from the powder material used, process-specific factors, such as geometry complexity, compaction pressure and lubrication strategy, have a major impact on the properties of the green compact. The lubrication strategy is also decisive for the economic efficiency of the process as it influences the service life of the tools. Friction-reducing powder-compaction tool coatings (e.g. diamond-like-carbon-based/DLC) provide the potential to positively influence the lubrication conditions during compaction and ejection, thus simultaneously improving product quality and service life. In this study, experimental investigations on the performance of friction-reducing coatings in the die pressing of steel powder (Fe + 0.6 wt% C) with and without admixed lubricant (AncorLube, GKN Hoeganaes) are presented. The results are evaluated by force-displacement measurements, which allows for a more profound analysis of compaction and ejection behaviour. It is shown that the application of the coatings reduces the ejection loads significantly when no admixed lubricant is used, and moderately when lubricant is admixed. However, without lubricant, wear still occurs after a few pressing cycles, so it cannot be completely avoided

Recycling of titanium alloys from machining chips using equal channel angular pressing

During the traditional manufacturing route, there are large amount of titanium alloys wasted in the form of machining chips. The conventional recycling methods require high energy consumption and capital cost. Equal channel angular pressing (ECAP), one of the severe plastic deformation techniques, has been developed to recycle the metallic machining chips. The purpose of the PhD work is to realize the ECAP recycling of titanium alloys, in particular Ti-6Al-4V and Ti-15V-3Cr-3Al-3Sn, and investigate the effects of processing parameters on the resultant relative density, microstructure evolution, texture development and microhardness homogeneity. The microstructures of Ti-6Al-4V and Ti-15V-3Cr-3Al-3Sn machining chips obtained from conventional turning (CT) and ultrasonically assisted turning (UAT) were initially investigated. It was found that ultrafine grains were formed in the primary and secondary shear zones. For Ti-6Al-4V chips, the β phase in the shear zones was refined into nano-sized equiaxed grains and aligned up to form banded structures. For Ti-15V-3Cr-3Al-3Sn chips, the nano-crystalline grains were enveloped in the shear zones and have clear boundaries to the surrounding matrix. It was observed that in terms of microstructure, there is no significant difference between CT and UAT chips. Recycling of Ti-6Al-4V machining chips was carried out at moderate temperatures with various back-pressures. For single-pass samples, the relative density was increased with the applied back-pressure and operating temperature. It was found that after multiple passes, near fully dense recycled Ti-6Al-4V can be fabricated. The microstructure observations showed that the nano-sized equiaxed and elongated grains co-existed with relatively coarser lamellar structures which were initially refined after the first pass. In the subsequent passes, the fraction of equiaxed nano-grains increased with the number of passes. The original β phase banded structures were fragmented into individual nano-sized grains randomly distributed within α matrix. The chip boundaries were eliminated and nano-crystalline microstructure region was observed at the chip/chip interface after multiple passes. In the sample processed at 550 °C, type dislocations were observed and oxide layer at chip/chip interface was detected. The texture evolution was investigated using electron backscatter diffraction. It was found that the recycled samples performed a strong basal texture along the normal to ECAP inclination direction after the first pass. After multiple passes, in addition to the normal to inclination direction, the recycled Ti-6Al-4V exhibits a basal texture towards the transverse direction. Microhardness mapping showed that the average hardness and degree of homogeneity were increased with number of passes, while the imposed back-pressure had little effect on the average value and homogeneity. Recycling of Ti-15V-3Cr-3Al-3Sn machining chips was implemented using similar ECAP conditions. The effects of processing parameters, such as back-pressure, operating temperature and number of passes, on the relative density were similar to those for Ti-6Al-4V. Microstructural characterization showed that equiaxed instead of needle shaped α precipitates formed in the β matrix due to the high dislocation density and sub-grain boundaries introduced during ECAP. In terms of microhardness, the maximum hardness was obtained at the specimen pressed at 450 °C. It was found that the applied back-pressure and number of passes enabled to improve the homogeneity, but had little effect on the average hardness.</a

Tungsten Carbide

Tungsten Carbide - Processing and Applications, provides fundamental and practical information of tungsten carbide from powder processing to machining technologies for industry to explore more potential applications. Tungsten carbide has attracted great interest to both engineers and academics for the sake of its excellent properties such as hard and wear-resistance, high melting point and chemically inert. It has been applied in numerous important industries including aerospace, oil and gas, automotive, semiconductor and marine as mining and cutting tools, mould and die, wear parts, etc., which also has a promising future particularly due to enabling to resist high temperature and are extremely hard

The effect of vibrational energy on the densification and interparticle friction of metal powders

The production of engineering components by the process of metal powder compaction and sintering is a rapidly expanding process. The filling of all parts of the die cavity to uniform densification prior to compaction is an essential part of the process if compacts of even density free from spalling are to be obtained. The research has the main objectives of showing how the variable parameters of vibrational energy will affect the densification of a range of powders having a wide variation of characteristics, into dies of restrictive sections. The mechanism of densification is essentially by reduction of interparticle friction and a shear cell has been devised to measure interparticle friction under various conditions of vibrational energy. [Continues.

Remanufacturing and Advanced Machining Processes for New Materials and Components

"Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems.