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In this study, the eect of milling speed on particle size and morphology of Cu25W composite powder produced by high-energy ball milling was investigated. For this aim, commercial elemental copper and tungsten powders were milled in a planetary-type ball mill for dierent milling durations. Ball-to-powder weight ratio was selected as 10:1. Three dierent milling speeds, namely 200, 300, and 400 rpm were used throughout the tests. In order to avoid agglomeration and to decrease the tendency of cold welding among powder particles, stearic acid in amount of 2 wt.% was used as a process control agent. The morphological and microstructural evolution of the milled powders was evaluated by scanning electron microscopy. In addition, the variation of particle size and powder morphology as a function of milling duration was determined. As a result of this eort, the milling duration was found to have strong eect on the structural evolution of the powder, and the optimum particle size as a function of milling speed was determined.

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In this study, arc-erosion experiments using contactors were performed under inductive loads for up to 40000 switching operations to investigate the effect of different current loads on the arc-erosion performance of electrical contacts. Determination of the mass loss was performed after every 5000 operations. The arc-eroded surfaces were examined using scanning electron microscopy. The chemical composition near the arc was determined by energy dispersive X-ray spectroscopy. The results show that the contact surfaces are greatly affected by arc-erosion, resulting in mass loss due to material migration and/or evaporation. In addition, the arc-affected zones become bigger with the increase in the number of switching operations, especially at 20 A. However, electrical cleaning improves the contact performance by reducing the contact resistance due to breakdown of the non-conducting oxide films formed between 20000 and 25000 switching operations at 20 A. The stationary contacts experience major erosion, whereas the movable contacts suffered less contact erosion under each current load.

This study is based upon the optimization of production parameters of Cu25W electrical contact material. Commercial elemental copper (Cu) and tungsten (W) powders were synthesized to produce Cu25W composite powder by mechanical alloying technique at various amounts of stearic acid via using a planetary type ball mill. The effect of amount of stearic acid on production of Cu25W composite powder was evaluated. In order to achieve true alloying among powder particles, it is necessary to establish a balance between cold welding and fracturing. Hence, different types of process control agents (PCA) were used to reduce excessive cold welding. Here, the effect of various amounts of stearic acid, namely 0, 0.5, 1, 2 and 3 wt.% on morphology and some properties of Cu25W composite powder were studied. The microstructural evolution of the milled powders was characterized by using scanning electron microscopy. The test results showed that the morphology and particle size distribution of the milled powders were changed considerably depending upon the variable amount of PCA. In addition, holding the same milling duration, different microhardness values were obtained for various amounts of PCA.