16776

16776

بررسي عوامل موثر بر تشكيل پوشش نانوساختار TiN بر روي فولاد H13 به روش PACVD

دكتري

شناسايي و انتخاب مواد

پاييز 1390

دكتر شمس الدين ميردامادي - دكتر فرزاد محبوبي

دكتر شاهرخ آهنگراني

مواد و متالورژي

1395/12/07

1/1/1900 12:00:00 AM

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%) an​d hydrogen (75%) using active net. The experiment parameters include: duty cycle percentage, deposition temperature, deposition time, frequency, applied voltage an​d combination of nitrogen, hydrogen, argon an​d titanium tetrachloride gases. Because of the complexity of the process, the required experiments were only designed based on two parameters of deposition temperature an​d duty cycle percentage. The temperatures of deposition process were selected 450, 470, 500 an​d 520 °C an​d duty cycles of 33%, 40%, 50% an​d 60% were selected as well. The microstructure, mechanical an​d chemical properties of the coatings were eva​luated 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 an​d 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 an​d 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 an​d TiN1.15 can be attributed to the coatings which have been deposited at 450, 485 an​d 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% an​d 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 an​d consequently loss of wear resistance of the coating. This means that more uniform an​d 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.