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Hot indentation of a thermoelastic coated half-space by a rigid punch is considered. The coating is assumed to be functionally-graded with all group of properties arbitrary varying with depth. The deformation of the half-space caused by the simultaneous mechanical and thermal loading is considered. The punch is subjected to a normal centrally applied force and preliminary heated to a uniformly distributed temperature. The contact problem is reduced to the solution of a system of dual integral equations over two unknown functions: Hankel transform of normal stresses and heat flux in the contact area. Heat flux is obtained using the bilateral asymptotic method. This method was sufficiently generalized to take into account additional function describing the displacements of the surface caused by thermal heating and obtain contact stresses. The solution is obtained in an analytical form which clearly demonstrates the dependence of the contact characteristics from the initial physical parameters of the problem. Numerical analysis is provided to illustrate the effect of the presence of the coating and its thickness on the results. Differences between the homogeneous and functionally-graded coatings is illustrated. [ABSTRACT FROM AUTHOR]

Diamond-Like Carbon (DLC) coatings have high wear resistance, hardness, biocompatibility and chemical inertness. Secondary structures, which formed at the track in dry friction conditions, provide friction reduction. Doping DLC with both metallic and non-metallic elements leads to a rearrangement of the structure of graphite clusters, a change in their properties, and facilitates the formation of secondary structures. In the present, the silicon atoms were used to create the compositional structure of DLC surface layers at the level of the crystal lattice. DLC-Si coatings with the thickness of 2 µm were deposited on a (Cr, Al, Si)N layer with the thickness of 3 µm formed on a steel substrate. DLC-Si layer was deposited by plasma-enhanced chemical vapor deposition using acetylene and tetramethylsilane. Nanoindentation in the wear mode was used to study the nanomechanical properties of the surface. Atomic force microscopy was used to visualize the surface morphology and wear traces. In this study, secondary structures were created in a microfriction process using a NanoScratch mode. The surface structures after microfriction was observed by atomic force microscopy, and the specific surface energy was measured. The specific volumetric wear rate of the coatings after microfriction was estimated. During microtribological testing with double squares the specific volumetric wear rate of DLC coatings was 5.39·10-14 m3/N·m for 0.8 % Si and 12.39·10-14 m3/N·m for 10 % Si. When tested in the form of scratches, the specific volumetric wear rate for the coating was for the DLC-0.8 % Si (1.22 – 10.71)·10-14 m3/N·m and for the DLC-10 % (6.17 – 49.55) ·10-14 m3/N·m. [ABSTRACT FROM AUTHOR]

[Display omitted] • Physical and mechanical properties were obtained for (1 0 0), (1 1 0) and (1 1 1) oriented Si wafers. • Certain directions of crack propagation were revealed for each orientation. • AFM allowed to obtain crack length and К 1C with high accuracy. • A correlation was established between К 1C , surface energy and Young's modulus. • A correlation was established between G 1C and microhardness H. Crack resistance of silicon wafers plays a vital role in development of MEMS technologies containing beam elements. In the present research, this characteristic was determined using the Vickers tip indentation method. The critical stress intensity factor K IC and fracture energy G IC of silicon wafers of (1 0 0), (1 1 0), and (1 1 1) crystallographic orientations were evaluated. The measurements were supplemented by imaging of indents using atomic force microscopy (AFM). The correlation of these parameters with the specific surface energy, Young's modulus E and microhardness H was conducted. The values of E and H were evaluated by nanoindentation. The dependences of K IC and G IC on the load of silicon wafers of (1 0 0), (1 1 0), and (1 1 1) orientations were obtained. [ABSTRACT FROM AUTHOR]