Electroabrasive Grinding of Titanium Alloy at Zero-Charge Potential
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ELECTROABRASIVE GRINDING OF TITANIUM ALLOY AT ZERO-CHARGE POTENTIAL S. Zaborski and E. Lunarska Specific features of the metal surface obtained for the zero-charge potential are used for the optimization of electroabrasive grinding of hardly workable titanium alloys. Due to the zero-charge potential obtained for WT3-1 alloy in an electrolyte used for the electroabrasive treatment of the metal in the process of electric grinding, we obtain a better stereometric structure of the metal surface as compared with the structure obtained as a result of mechanical grinding.
Introduction In the process of electrogrinding of a metal, the applied anodic polarization causes the dissolution of the material and the formation of the oxide layer, whereas the mechanical action of the abrasive tool removes the oxide layer and activates the treated surface. This leads to the increase in the treatment yield for hardly machinable metals, such as Ti and its alloys. However this treatment is quite energy consuming and may result in the formation of surfaces with high roughness. Therefore, the conditions of treatment providing the optimum combination of the treatment yield, quality of the treated surface, and energy consumption should be selected. Thus, the modifications of grinding tools [1] and chemistry of electrolytes [1], as well as the application of various polarizations [1, 2] were considered. Since the poor workability of Ti alloys originates from their high plasticity and the possibility of chips to stick to the machined surface, the increase in the hardness of machined surface might produce a beneficial effect. It is known that the metal surface immersed in the electrolyte attains its highest hardness under the conditions of zero-charge potential (ZCP) [3, 4]. Therefore, the application of this potential may lead to the improvement of surface treatment of the metal. It should be noted, however, that the metal surface possesses the other critical properties at the ZCP, namely, the highest adsorption ability and the lowest wettability [3]. On the other hand, the evaluation of the ZCP is not easy, since it depends not only on the metal but also on the chemistry of the electrolyte [3]. Therefore, in order to apply the ZCP in electrogrinding, its value in the used electrolyte should be estimated. The aim of the present work is to evaluate the ZCP of WT3-1 alloy in an electrolyte used for electrogrinding and compare the surface quality of the metal ground mechanically and electromechanically with application of the ZCP. Materials and Experimental Procedure The specimens (1 cm2 in diameter) were machined from commercial WT3-1 Ti alloy and tested in a solution of 8 wt.% NaNO3 and 2 wt.% Na2 CO3 in water. The ZCP was evaluated by observation (through an oscilloscope) of the transient potentials in the course of systematic multiple application of anodic and cathodic polarizations to the freshly cleaned surface. The ZCP corresponds to the transient potential recorded when the current is equal to zero. Wrocław Technical University, Poland;
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