Artur Shugurov

Fractal analysis of electromigration-induced changes of surface topography in Au conductor lines

Evolution of surface morphology of Au conductor lines under high-density electric current is studied by scanning tunneling microscopy. The loss of conductivity of thin Au films is found to occur through formation of voids resulted from electromigration followed by the depletion of the material. It is shown that the density of electric current passing through thin conducting films greatly affects their lifetime. Fractal analysis is employed to estimate numerically changes of surface topography of Au films. The fractal dimension is shown to be an optimum prefracture criterion for thin metal films under applying electric current.

The effect of Al intermediate layer on thermal resistance of EB-PVD yttria-stabilized zirconia coatings on titanium substrate

The yttria-stabilized zirconia coatings sprayed on titanium substrates by the electron beam physical vapor deposition were subjected to thermal annealing in air at 1000°C for 1, 30 and 60 min. The delamination and fracture of the coatings are studied by the scanning electron microscopy and X-ray diffraction. It is shown that a magnetron sputtered Al interlayer between the coating and the substrate considerably improves the thermal resistance of ceramic coatings.

Effects of nitrogen and argon ion implantations on surface morphology, microstructure, and mechanical properties of Ti-Al-N coatings

The surface morphology, microstructure, and mechanical properties of magnetron sputtered Ti-Al-N coatings implanted with nitrogen and argon ions were studied using atomic force microscopy, X-ray diffraction, and nanoindentation. The implantation was found to result in a considerable decrease in the surface roughness of the coatings as well as the formation of amorphous and nanocrystalline structure of the modified surface layer with incorporated gas bubbles. The latter induced softening of the coatings, especially pronounced at shallow indents.

The effect of laser treatment of WC-Co coatings on their failure under thermal cycling

The given paper studies the effect of surface laser treatment of WC-Co coatings on their surface morphology, phase composition and thermal cycling behavior. The coatings were sprayed on stainless steel substrates with the use of a high velocity oxy fuel spraying process. Application of the scanning electron microscopy and X-ray diffraction showed that re-melting of the coating surface layer during laser treatment induced changes in its phase composition as well as the formation of regular rows of globular asperities on the coating surface. The latter resulted in a sharp increase in thermal shock resistance of the laser treated WC-Co coatings under water quench tests; its underlying mechanism are proposed and discussed in the paper.

Fracture toughness and oxidation resistance of Ti-Al-N coatings on stainless steel substrates

The effect of preliminary ion bombardment of a stainless steel substrate on the fracture toughness and oxidation resistance of Ti-Al-N coatings was studied using scanning and transmission electron microscopy, X-ray diffraction and nanoindentation. The ion-beam treatment of the substrate was shown to substantially affect the microstructure and the hardness of the coatings as well as to improve their fracture toughness estimated from scratch tests. In addition, it resulted in higher oxidation resistance of the Ti-Al-N coatings under thermal cycling.

Improvement of the wear resistance of electroplated Au-Ni coatings by Zr ion bombardment of Ni-B sublayer

The effect of bombardment of the Ni-B sublayer by Zr ion beams on the surface morphology and tribomechanical properties of Au-Ni coatings was investigated. It was found that the treatment has no significant effect on the surface roughness and grain size of the Au-Ni coatings, while it provides essential reducing of their friction coefficient and improvement of wear resistance. It is shown that increased wear resistance of these coatings was caused by their strain hardening resulted from localization of plastic strain. The optimal Zr fluence were determined that provide the maximum reduction of linear wear of the coatings.

Mechanisms of stress generation and relaxation in thin films and coatings

The failure modes of thin metal films and ceramic coatings induced by both intrinsic (growth) stresses and external effects (uniaxial tension, alternating bending, thermal treatment) were studied. Stress relaxation that causes soft films and hard coatings to fail was demonstrated to be governed by essentially the same mechanisms. The primary factor governing the reliability of thin-film structures was shown to be the strength of the film/substrate interface.

Surface Morphology, Microstructure and Mechanical Properties of Thin Ag Films

Thin Ag films deposited onto SiO/sub 2//Si substrates by DC magnetron sputtering and thereafter annealed at temperatures 100-500/spl deg/C are investigated by scanning tunneling and atomic force microscopy. It is shown that the film surface topography and microstructure are considerably changed as a result of annealing. To provide a quantitative estimation of the surface topography changes of Ag films the surface fractal dimension was calculated. Elasticity and hardness of the films are studied by a nanoindentation technique. The films are found to have value of elastic modulus close to that of bulk silver while their hardness and yield stress are essentially higher.