Effect of Nitrogen Pressure and Substrate Bias Voltage on Structure and Mechanical Properties of Vacuum Arc Deposited VN Coatings

Abstract

The binary vanadium–nitrogen (V–N) coatings were formed using cathodic arc evaporation. Two sets of coatings were produced using: (a) nitrogen pressure (pN2) from 0.001 Pa to 3 Pa at a constant substrate bias voltage (UB) of − 100 V and (b) a substrate bias voltage from − 50 to − 300 V at a constant nitrogen pressure of 1.5 Pa. The influence of the above parameters on the coating properties, in particular on the insufficiently investigated and described adhesion of the coatings to the substrate, was demonstrated. The phase transformation V → V + V2N → V + c-VN → h-VN → h-VN + c-VN and c-VN → h-VN occurs for coatings formed with increasing nitrogen pressure and substrate bias voltage, respectively. With the increase in pN2 and UB, an increase in coating hardness and adhesion to the substrate is observed, as well as an improvement in wear resistance.

Impact of sputtering gas on the microstructural, mechanical and wetting properties of vanadium nitride coatings

“…At 20% N 2 partial pressure, a prominent diffraction peak corresponding to FCC-VN phase with (220) as crystalline plane is detected, along with minor (111) and (200) peaks. This suggests the presence of VN at 20% N 2 partial pressures, the absence of pure V indicates conversion of V to VN by filling interstitial sites with nitrogen atoms, in line with the observations made by Kuprin et al [27]. Coatings deposited at N 2 partial pressures of 40%, 60%, and 80% all exhibited the FCC-VN phase, characterized by a prominent peak at the (200) plane.…”

Mechanical Properties of V-O-N Coatings Synthesized by Cathodic Arc Evaporation

“…Other reflections of this phase (001) and ( 101) are much weaker in the diffractograms, and reflections (110), (002), ( 111), (102) are not detected at all, which is due to the formation of a sufficiently strong axial texture with a predominant orientation of crystallites with planes (h00) parallel to the surface of the sample, i.e., the location of the crystal lattice hexagons with the c-axis in the coating plane. A similar arrangement of hexagons was previously observed in α-Ti vacuum-arc coatings [32], but in h-VN coatings, the predominant orientation of crystallites was found to be with the base planes (00l), i.e., the c-axis perpendicular to the surface [33]. The phase identification was performed according to the International Centre for Diffraction Data (ICDD) pattern.…”

“…The coating formed without nitrogen is characterized by a hexagonal structure, and the addition of oxygen changes the structure to a cubic one, Figure 5. Previous studies have shown that the hexagonal vanadium nitride coating is characterized by higher hardness than the coating with a cubic structure [33,51].…”

“…[55,56]. The change in the predominant orientation in h-VN coatings from (00l) to (h00) is most likely due to a decrease in the substrate rotation speed from 30 [33] to 9 rpm and the substrate-cathode distance of 400 mm.…”

“…Vacuum-arc coatings deposited on a substrate at a low substrate bias voltage of −50 V have the same c-VN structure. As the bias, and therefore the ion energy, increases, the phase transformation c-VN → h-VN occurs, and in the range of 150-300 V, only h-VN is detected [33]. According to the theoretical first-principles study of the phase stability of stoichiometric vanadium nitrides, it is the WC-based VN x structures for x > 0.8 that appear to be the most stable, although the c-VN x phase predominates in experiments over a wide range of concentrations and synthesis temperatures [35].…”