Electrical discharge coating of ceramic metal composite on metal substrate using powder compact electrodes

EDM is a prominent non-traditional machining process, which is widely used for machining hard materials those are not possible by conventional processes. A very special aspect of this process is surface modification by material transfer from the tool electrode to the work-piece which is commonly known as an electro discharge coating (EDC). In this work, electrode prepared with tungsten (W)-copper (Cu) and with titanium carbide (TiC)-copper (Cu) powder by powder metallurgy (PM) route used as tool material and pure aluminum and AISI 1020 mild steel are used as work-piece. Using reverse polarity (tool as anode and work-piece as cathode) in electro discharge machine hard composite layer of WC-Cu on Aluminium substrate and TiC-Cu on AISI 1020 mild steel substrate have been deposited. The effect of compaction pressure during tool preparation by PM method and peak current (Ip) and pulse on time (Ton) during the EDC process on Deposition Rate (DR), Tool Wear Rate (TWR), Micro Hardness has been studied. Surface roughness of the coated surface have also been measured. Microstructures of the deposited layers are studied by using the optical images, while the compounds present in the coating are analyzed by XRD (X-Ray Diffraction) technique

Deposition of TiC-Cu composite coating on AISI 304 stainless steel by EDC process using powder compact tool electrode

623-630In this work, powder compact tool electrode prepared with TiC-Cu powder mixture has been used to deposit TiC coating on AISI 304 stainless steel by electro discharge coating (EDC) process. Effects of peak current during EDC process have been analysed for the deposition rate, surface characteristics and micro-hardness value of the coating. Morphology of the deposited coating layers has been studied by the scanning electron microscopy (SEM) images while the compounds present in the coating layer have been analysed by X-Ray Diffraction (XRD) technique. Wear rate of the coated samples has been measured by ball-on-disc type sliding wear test against WC-Co ball. The experimental results revealed that higher peak current during the EDC process augmented the deposition rate and corresponding coating thickness. Micro-hardness value and wear resistance of the deposited coating has been found significantly improved than those of as received substrate material

Deposition of TiC-Cu composite coating on AISI 304 stainless steel by EDC process using powder compact tool electrode

In this work, powder compact tool electrode prepared with TiC-Cu powder mixture has been used to deposit TiC coating on AISI 304 stainless steel by electro discharge coating (EDC) process. Effects of peak current during EDC process have been analysed for the deposition rate, surface characteristics and micro-hardness value of the coating. Morphology of the deposited coating layers has been studied by the scanning electron microscopy (SEM) images while the compounds present in the coating layer have been analysed by X-Ray Diffraction (XRD) technique. Wear rate of the coated samples has been measured by ball-on-disc type sliding wear test against WC-Co ball. The experimental results revealed that higher peak current during the EDC process augmented the deposition rate and corresponding coating thickness. Micro-hardness value and wear resistance of the deposited coating has been found significantly improved than those of as received substrate material

Attribution and contestation: Relations between elites and other social groups

In this article we explore the often ambiguous relations between elites and other social groups, both subordinate and of relatively equal standing. The article draws on two distinctive ethnographic cases: the white Franco-Mauritian elite, and the expert elite of management consultants in a Western European context. Our analysis of the two cases provides insights into how the power and status of elites is both contested and attributed by the people they interact with and relate to in concrete, yet substantially different contexts and situations. The aim is to show how the position and power of different kinds of elites is relationally negotiated and achieved. As we argue, a better understanding of the role of other social groups in the attribution, maintenance and contestation of status is relevant for understanding both more traditional economic elites and expert elites without tight networks

In-situ TiC-TiB2 coating on Ti-6Al-4V alloy by powder suspension electro-discharge coating (EDC) and tungsten inert gas (TIG) cladding processes

Ti-6Al-4V is one of the most attractive and frequently used Ti alloy in various industrial applications due to its excellent properties including high specific strength, corrosion resistance, and high melting temperature. However, the application of Ti-6Al-4V alloy is restricted under severe wear and frictional conditions owing to its low hardness and poor wear resistance. Hence, surface modification of Ti-6Al-4V alloy becomes important to extend its possibility of application. In the present research work, TiC-TiB2 composite coating has been fabricated on Ti-6Al-4V alloy to enhance its tribological properties by powder suspension electro-discharge coating (EDC) method and TIG cladding process through in-situ reactions between Ti and B4C powder mixture. The microstructure analysis of the coating has been executed through scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) images, electron probe micro-analyzer (EPMA) and electron dispersive spectroscopy (EDS). The compound phases formed via in-situ reaction of Ti and B4C have been identified by X-ray diffraction (XRD) technique. The micro-hardness values of the coating have been measured using Vickers micro-indentation hardness tester and wear behaviour of the coating has been analyzed by pin-on-disc and ball-on-disc sliding wear test. With reference to the available literature, SEM images of the blended precursor powder mixture and coating layer, EPMA images and XRD analysis of the produced coating, the formation mechanism of the present TiC-TiB2 composite coating during TIG cladding process has been elucidated. The coating produced by EDC process shows upto three times increase in the hardness value and seven times higher wear resistance against WC-Co ball than the uncoated Ti-6Al-4V substrate. Further, the coating produced by TIG cladding method under different processing condition exhibited up to four times increased hardness and three times higher sliding abrasive wear resistance (against alumina abrasive disc) than the as-received Ti-6Al-4V alloy substrate. The fracture toughness of the coatings produced by TIG cladding method as measured by indentation method was found (5.65–6.97 MPa.m1/2), much higher than that of individual TiB2 or TiC phases. The effect of processing current employed during the TIG cladding and the effect of Ti and B4C ratio on the morphology and mechanical behavior of the produced TiC-TiB2 coatings have also been investigated. The microstructural analysis of the produced composite coating revealed that at relatively low current, the coating layers are not appropriately bonded with the substrate; whereas, for employing higher current, owing to high heat input, mixing of the coating material with the substrate surface becomes appreciable. Significant variation in the hardness and wear value was recorded for the alteration of the processing current, and Ti and B4C powder ratio, which was mainly attributed to the variation in the proportion of hard TiC and TiB2 phases and dilution of the substrate material with the clad layer