Effects of Duty Cycle on Nanostructured TiN Coatings on AISI H11 and AISI D2 Steels

This study focuses on the effects of duty cycle on morphology, hardness, structure, corrosion resistance, and chemical composition of nanostructured titanium nitride (TiN) coatings deposited by plasma-assisted chemical vapor deposition (PACVD) on two tool steels AISI H11 hot work and AISI D2 cold work. The PACVD was performed at 475 °C for 2 h in a chamber containing Ar, N₂, and H₂ gases along with TiCl₄ vapor at a pressure of 2 mbar, for various duty cycles of 33, 50 and 60%. The coatings were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, hardness, and potentiodynamic polarization. The results indicated that the surface roughness and corrosion rate at the 33% duty cycle were lower than those of the other two cycles. It was also revealed that the finer grains formed at the lower-duty cycles played an important role in lowering the corrosion rate. Also, thin films deposited at lower-duty cycles had higher hardness. The higher chlorine content in the lower-duty cycles did not affect the surface properties of the nanostructured TiN coatings.