Mechanical and corrosion properties of hydrogen-free DLC coatings prepared on degradable as-extruded WE43 alloy using FCVA technology

Abstract

Magnesium alloys have great potential for medical applications. However, their rapid degradation has limited their development. Hydrogen-free DLC coatings were deposited on WE43 using filtered cathodic vacuum arc (FCVA) technology. The influence of different negative bias voltages on the microstructure and mechanical and corrosion properties of the coatings was systematically analyzed. The research demonstrated that application of a negative bias voltage altered the surface morphology of hydrogen-free DLC coatings with amorphous structures. In addition, the coatings exhibited a decrease in hardness and elastic modulus until the negative bias voltage reached −75 V, indicating that the increase may be attributed to the rise in sp2 cluster size and the fall in sp3 content. Furthermore, electrochemical experiments demonstrated that the coated samples exhibited superior anti-corrosion properties. The coatings deposited at −75 V displayed the highest corrosion resistance, as evidenced by their minimal corrosion current (4.53 μA·cm−2), maximal film resistance (2576 Ω·cm2), and charge transfer resistance (3171 Ω·cm2). Hydrogen evolution experiments indicated that the hydrogen-free DLC coatings effectively reduced WE43 corrosion and hydrogen gas production.