Abstract
In this study, electrospark-alloying (ESA) method was employed to coat a titanium alloy with hard material (tungsten carbide). The role of titanium oxide film on the ESA process was investigated. Due to presence of the oxide film, the formation of unusual erosion and mass transfer mechanism in electrodes different from conventional ESA process were observed during the process. It was deduced that these cause some failure of deposited coating layer such as “washing away” and cavities formation in and/or under coating layer. To achieve a good quality coating, this study primarily focused on the electrical parameters of alloying process and then limiting time intervals of process were defined where there were failures of the coatings. Using electrical pulses with energy of 0.34 J (current amplitude of 200 A, pulse duration of 120 μs), it was possible to obtain a uniform coating layer with an average thickness of 52 μm.

Key words
coating, electrospark alloying, titanium, titanium oxide film

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