Effects of duty cycle on microstructure and corrosion behavior of TiC coatings prepared by DC pulsed plasma CVD

Titanium carbide coatings are deposited on hot-work steel (H11) by plasma-assisted chemical vapor deposition (PACVD) and the dependence of the corrosion behavior on fabrication parameters is investigated. Grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), Raman and electrochemical tests are used to study the structure as well as corrosion behaviors. Grazing incidence X-ray diffraction reveals the (2 0 0) plane implying that the TiC coatings are deposited via the kinetics-limited crystal growth mechanism and under thermodynamically stable conditions. The SEM results indicate that the formation of a homogeneous and uniform titanium carbide nanostructure coatings. Potentiodynamic and electrochemical impedance tests performed in 0.5 M H2SO4 and 0.05 M NaCl show that the TiC coating produced using a 40% duty cycle possesses high corrosion resistance in both media. The Rp values of the TiC coating (50% duty cycle) in 0.05 M NaCl and the other TiC coating (40% duty cycle) in 0.5 M H2SO4 are approximately four and sixteen orders of magnitude higher than that of the bare steel, respectively. Our results reveal that the duty cycles not only affect the structure and morphology of the coatings but also influence the electrochemical properties.