Pulsed laser deposition of composite Mo-Se-Ni-C coatings using standard and shadow mask configuration

Thin film Mo-Se-Ni-C coatings for tribologycal applications were prepared by pulsed laser co-deposition from two targets - MoSe2(Ni) and graphite. Two methods of deposition from the MoSe2(Ni) target were used: deposition with unhindered expansion of the laser plume (standard PLD) and deposition of a plume scattered in collisions with Ar gas (pressure 2 Pa) in the shadow of a mask (shadow-masked PLD - SMPLD). Doping with carbon by PLD was used in all cases, and carbon content in the composite Mo-Se-Ni-C coatings was varied in the range 35-85.5 at.%. Pure MoSex(Ni) coatings were also prepared by PLD and SMPLD. Rutherford bacicscattering spectroscopy of helium ions, scanning electron and atomic force microscopy, electron probe microanalysis, transmission electron microscopy and micro-diffraction, micro-Raman spectroscopy, X-ray photoelectron spectroscopy and hardness evaluation were all used for comparative studies of the coatings obtained by RD and SMPLD/PLD. In the PLO coatings, micron-sized particles were found, consisting of pure Ni or MoSe2, as well as nanometre-sized particles of monocrystalline Mo. The nanoparticles were distributed on the surface and in an amorphous matrix in all PLO coatings. Within the amorphous matrix of the Mo-Se-Ni-C coatings, local ordering of atoms was detected, causing the formation of a mixture of amorphous carbon, Mo-C, and Mo-Se phases. Increasing the carbon content caused an increase in the content of sp(3) bonds in the carbon phase, and an increase in the hardness of the coatings. SMPLD/PLD coatings had no micro- and nanoparticles, but these coatings were characterized by high selenium content and reduced density. Doping with carbon in the SMPLD/PLD configuration caused the formation of composite coatings containing Mo-Se and amorphous carbon phases as in the PLD coatings, but the hardness of the composite SMPLD/PLD coatings was significantly lower than even the hardness of the pure PLD MoSex(Ni) coatings. (C) 2012 Elsevier B.V. All rights reserved.