Abstract
In this study, DLC films were deposited using IBED with various CH4/H2 ratio, gas flow rates and accelerating voltages. The composition and mechanical properties of the DLC coatings were characterized using SEM, Raman spectroscopy and nanoindentor. The tribological properties of the coating were also investigated using a frictional surface microscope with an in situ observation system and friction force measurements. The DLC films were characterized by a lower ID/IG, higher hardness, and improved tribological properties when deposited at a lower accelerating voltage (6 kV). At the CH4/H2 ratio of 1:99 and 6 sccm/6 kV, minimum ID/IG values of 0.62, relatively low friction coefficient of 0.12 , and a maximum hardness of 4056 HV were attained respectively.
Highlights
Magnesium alloys have been widely used because of their light weight, high dimensional stability, excellent machinability and so on [1, 2]
An increase in the hardness and reduction of the friction coefficient were observed in another study in which Diamond-like carbon (DLC) coatings were deposited on magnesium alloys, which led to improvement of the wear resistance [7]
The ID/IG ratios increased and the G-peak position shifted toward higher wavenumber with increasing accelerating voltage at CH4/H2 ratio of 99:1, and ID/IG decreased and the G-peak position shifted toward lower wavenumber with increasing gas flow rate at 6 kV
Summary
Magnesium alloys have been widely used because of their light weight, high dimensional stability, excellent machinability and so on [1, 2]. Diamond-like carbon (DLC) films exhibit high hardness, low friction, excellent wear resistance and so on [4]. Liu et al deposited a DLC film on metallic substrates using a methane ion-beam method and observed that the ultra-low wear rate was due to transfer layer formation of graphite-like carbon [5]. Dai et al reported that magnesium alloy coated with Cr-incorporated DLC hard films had a low internal stress and excellent friction performance [6]. An increase in the hardness and reduction of the friction coefficient were observed in another study in which DLC coatings were deposited on magnesium alloys, which led to improvement of the wear resistance [7]. Relative to chemical and thermal processes, the IBED method has many advantages when used to enhance the friction, adhesion, and other surface properties of high-precision parts, as it does not require post-coating refinish
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