چكيده به لاتين
Abstract
In this study, TiN coating was deposited on hot work AISI H13 steel using plasma assisted
chemical vapor deposition method. In order to obtain desirable properties of the coating, before deposition process, the test medium was plasma nitrated by gas mixture of nitrogen (25%) and hydrogen (75%) using active net.
The experiment parameters include: duty cycle percentage, deposition temperature, deposition time, frequency, applied voltage and combination of nitrogen, hydrogen, argon and titanium tetrachloride gases. Because of the complexity of the process, the required experiments were only designed based on two parameters of deposition temperature and duty cycle percentage. The temperatures of deposition process were selected 450, 470, 500 and 520 °C and duty cycles of 33%, 40%, 50% and 60% were selected as well. The microstructure, mechanical and chemical properties of the coatings were evaluated by optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM) equipped with nano-indenter, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), microhardness test, nano-indentation test, roughness and wear tests. According to the results, by increasing deposition temperature from 450 °C to 520 °C, grain sizes of the coating increases from 4 nm to 12 nm and increase of duty cycle at 450°C leads to the increase of grain size from 4.6 nm to 5.9 nm. Non-stoichiometric compositions of TiN0.85, TiN1.11 and TiN1.15 can be attributed to the coatings which have been deposited at 450, 485 and 520 °C respectively. The thickness of the coating layers decreased from 2.3 nm to 1.5 nm by increasing duty cycle from 33% to 60% and by the increase of deposition time from 4 to 6 hr, it has been increased from 2 nm to 3.5 nm. The calculated values for texture coefficient indicate that the preferred growth direction for TiN coating is the normal direction of (200) plane.
Increasing deposition temperature leads to the increase of surface roughness from 10 to 72 nm.
In addition, by increasing duty cycle from 33 to 50%, surface roughness increases from 41 to 90 nm which causes further peeling of the coating and consequently loss of wear resistance of the coating. This means that more uniform and polished coating leads to the more wear resistant coating.
Keywords: hot work H13 steel, net assisted plasma nitrating, plasma assisted chemical vapor deposition, duty cycle, wear properties.
