In this study, cathodic arc physical vapor deposition process was used in a novel approach. Application of different bias voltages during coating and diffusion processes facilitates the production of titanium-aluminum intermetallic layers on the titanium substrate. This method was applied by two different processes, depending on the type of bias power supply.
In the first process, bias voltage is applied by means of direct current power supply. Aluminum layer was deposited on a titanium surface using low bias voltage in cathodic arc plasma. After the deposition of aluminum layer, titanium surface was bombarded increasing the bias to higher voltages in the same ion plasma to form the intermetallic phases of the titanium and aluminum. In consequence of the bombardment process, aluminum rich titanium-aluminum intermetallic layer was formed on the titanium surface. In the next step, the intermetallic layer was further bombarded to modify the phase constituents.
In the second process, bias voltage is applied by alternating current power supply. In alternating current, bias changes to negative and positive voltages alternative periodically. In the negative voltage period, aluminum ions are pulled to titanium substrate surface and a coating is formed. In the positive voltage period, electrons are pulled to substrate and newly formed coating surfaces. This process is called electron heating and can be used to enhance the diffusion process between the substrate and the coating. By controlling the bias current, temperature of substrate surface can be controlled. As a result, titanium-aluminum intermetallic layers consisting of different Ti-Al phases were produced. |