Influence of positive pulse voltages on structure, mechanical, and corrosion inhibition characteristics of Si/DLC coatings

In this study, Si/DLC films were effectively deposited on 2024-Al alloy using a plasma-enhanced chemical vapor method at different pulse voltages. Scanning electron microscopy, X-ray diffraction spectroscopy, 2D optical profilometer, Raman spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the structure of the DLC coatings. The adhesion strength was performed using Scratch Tester. Further, the Nano Indenter G200 apparatus was used to measure the hardness and Young's modulus of coatings. The Ball-on-Disk Tester was used to measure the friction coefficient of the specimens. A Potentiostat/Galvanostat electrochemical workstation was used to examine the corrosion performance and passive stability of DLC coatings in 3.5 wt% NaCl solution. The findings demonstrated that the thickness of the coatings increased with increasing the pulse voltage to 1800 V, causing an improvement in mechanical properties and corrosion resistance. This is due to an increase in the amount of sp3 hybrid in the coating, which reduces the electrical conductivity of DLC and limits electron transfer and electrical charge exchange at the coating surface. However, the corrosion rate of the coatings increased when the pulse voltage increased to 2200 V. •Si/DLC coatings were deposited on Al-2024 alloy using the PECVD technique.•Increasing pulse voltage to 1800 V enhanced the mechanical properties.•Reduction in structural connectivity of coatings increased its corrosion rate.