High‐speed wire electrical discharge machining to create superhydrophobic surfaces for magnesium alloys with high corrosion and wear resistance
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Abstract Herein, a superhydrophobic surface of AZ31B magnesium alloy prepared by high‐speed wire electrical discharge machining and modification with stearic acid is reported. The surface morphology and wettability of the superhydrophobic surface were investigated by scanning electron microscopy and optical contact angle measurement, respectively. A uniform micro‐/nanopetal‐like structure was shown within the superhydrophobic surface, resulting in a contact angle of 151 ± 0.5° and a sliding angle of 4 ± 0.5°. Notably, the superhydrophobic surface had better corrosion resistance than the bare magnesium alloy, and its corrosion current density was reduced by nearly one order of magnitude. Under both dry and wet friction conditions, the friction coefficient of the superhydrophobic surface was lower than that of the bare magnesium alloy surface, with a much lower wear loss. In addition, the friction coefficient of the superhydrophobic sample was lower than that of the bare magnesium alloy sample under both the dry and wet friction conditions. Thus, the superhydrophobic sample experienced reduced wear and had a low wear rate.Keywords:
Electrical Discharge Machining
Surface wettability is one of the crucial characteristics for determining of a material’s use in specific application. Determination of wettability is based on the measurement of the material surface contact angle. Contact angle is the main parameter that characterizes the drop shape on the solid surface and is also one of the directly measurable properties of the phase interface. In this chapter, the wettability and its related properties of pristine and modified polymer foils will be described. The wettability depends on surface roughness and chemical composition. Changes of these parameters can adjust the values of contact angle and, therefore, wettability. In the case of pristine polymer materials, their wettability is unsuitable for a wide range of applications (such as tissue engineering, printing, and coating). Polymer surfaces can easily be modified by, e.g., plasma discharge, whereas the bulk properties remain unchanged. This modification leads to oxidation of the treated layer and creation of new chemical groups that mainly contain oxygen. Immediately after plasma treatment, the values of the contact angles of the modified polymer significantly decrease. In the case of a specific polymer, the strongly hydrophilic surface is created and leads to total spreading of the water drop. Wettability is strongly dependent on time from modification.
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