Deposition process and characterization of chromium-carbon coatings produced by direct sputtering of a magnetron chromium carbide target

Abstract

Chromium-carbon coatings have been deposited on various substrates by direct sputtering of a chromium carbide, Cr3C2, target in pure argon atmosphere. The composition of coatings determined by Rutherford backscattering spectroscopy and the deposition rate were investigated as functions of the sputtering gas pressure and self-bias voltage applied to substrates. The atom number ratio C/Cr in the coatings was equal to 0.7 regardless of the deposition conditions investigated. Oxygen and argon atoms were the major impurities incorporated in the amorphous coatings. Oxygen-free Cr-C coatings were prepared at low argon pressures or on substrates biased to a voltage in the range −100 to −320 V. The Cr-C coatings deposited on biased substrates contained less than 2 at. % of argon. The morphological features of Cr-C coatings examined by scanning electron microscopy were also dependent on the sputtering gas pressure and bias voltage of substrates. Fully dense structures were observed for coatings deposited at low argon pressures or on biased substrates. The electrical resistivity of Cr-C coatings was extremely dependent on the concentration of oxygen atoms incorporated in the coatings. Oxygen-free Cr-C coatings exhibited electrical resistivity values as low as 120 μΩ cm, i.e., less than twice the bulk resistivity of Cr3C2. The residual stresses in the coatings and microhardness of the deposited material were also investigated as functions of the deposition parameters. Tensile residual stresses were lower than 0.8 GPa, and the maximum microhardness of coatings was about 13000 MPa, i.e., similar to that of the bulk material.

Pulsed laser deposition from a pre‐synthesized Cr2AlC MAX phase target with and without ion‐beam assistance

“…For MgO substrate, the ion‐beam improves the conductivity and for the SiO 2 substrate, but there is no clear trend. The measured conductivities are also consistent with values measured for chromium/carbon films with sheet conductivities of 0.1 × 10 6 –0.8 × 10 6 (Ω · m) −1 19.…”

“…The hardness for the films deposited on the stainless steel substrates increases with temperature when no ion‐beam is used and decreases with temperature, when the additional ion‐beam is used during PLD. The observed values are comparable to those measured for films consisting only of chromium and carbon, exhibiting hardness values of 7–12 GPa 19.…”

“…Soon after the first publications of the interesting properties of MAX phases, research was also directed towards the preparation of MAX thin films and coatings. Numerous interesting reports on the successful synthesis of MAX thin films with various elemental compositions have been published 11–31. A very extensive and critical overview of the research progress in the deposition of MAX thin films and their materials science is given by Eklund et al 21.…”

Influence of the bias voltage on the structure and the tribological performance of nanoscale multilayer C/Cr PVD coatings

“…The coating deposited at Ub = -65 V is considerably rougher but it becomes smoother and denser as the bias voltage is increased from -65 to -350V. This is due to the effects of bombardment of the growing films by energetic particles, which enhances the surface mobility of the condensed species, promotes the displacement of surface atoms towards more stable positions in terms of surface energy, and results in the elimination of voids, cavities, and vacancies in the coatings [27]. The coatings deposited between -65 and -95 V show columnar structures with carbon accumulated at the grain boundaries (the white phase between the columns) [17], as shown in Fig.…”

Phase composition of Cr-C thin films deposited by a double magnetron sputtering system

“…2(a), is <40 at.%; films with high resistivity ½ 1400 Ðcm , in the area where the carbon concentration is >55 at.%; and a transition area where the carbon concentration is 40-55 at.%. For comparison, according to Refs 3, 9 and 17, the resistivities of pure Cr, graphite and the highcarbon crystalline υ-phase Cr 3 …”