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This work investigates the influence of process parameters on microstructure, adhesion of layers to the substrate and wear resistance of Ni/MoS2 micro- and nanocrystalline composite layers. Pure nickel coatings were also fabricated and tested for comparison. The layers were deposited by electrochemical reduction on pure A2 aluminum and on PA6 alloy. The layers were produced at a current density of 3 A/dm2 and a mixing speed of 400 rpm. The bath composition was also modified by the addition of saccharin and the disperse phase of molybdenum disulfide in the bath (2.5 and 5 g/l). Materials prepared in this way underwent structural investigations (using scanning electron microscopy and optical microscopy), a scratch test and tribological tests (using a ball-on-disc method). The results of the tests allowed to determine the dependence of the structure and properties of the produced coatings on the production parameters. The composition of the electrolyte affects the size of crystallites as well as the morphology and topography of the surface. The scratch test confirmed the good adhesion of the nickel and composite layers to the substrate. The best lubricating properties were shown by nanocrystalline coatings. The too high content of molybdenum disulfide in the bath caused an undesirable increase in the coefficient of friction.

Mathematical modelling of single and consecutive dual - frequency induction surface hardening systems are presented and compared. The both models are solved by the 3D FEM-based professional software supported by a number of own numerical procedures. The methodology is illustrated with some examples of surface induction hardening of a gear wheel made of steel 41Cr4. The computations are in a good accordance with experiments provided on the laboratory stand.

Corrosion behaviour of carbon steel (K-55) in fracturing fluid was studied with a rotation cylinder electrode, under static and rotation conditions by means of several electrochemical techniques which are as follows: open circuit potential (OCP) decay, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). The corrosion rate was determined by weight loss measurements. The electrode surface after a prefixed immersion time was characterised by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that carbon steel showed anodic dissolution behaviour that increased under rotating condition. The cathodic polarisation current density also increased with the electrode rotation due to the increased oxygen diffusion on the electrode surface. Two different oxide layers were formed: a dark, thin layer of magnetite tightly adhering to the electrode surface, characterised by localised corrosion spots, and a porous reddish layer of poorly adhering hematite (Fe2O3) and maghemite (γ-Fe2O3). Under higher rotation rate, the developed oxide layer was not so stable, owing to the shear stress induced between the solution and the specimen surface, enhancing the corrosion rate.

This study is concerned with the modification of titanium surface by plasma electrolytic oxidation (PEO) and hydrothermal treatment. The samples were oxidized in an electrolytic solution that contained calcium β-glycerophosphate and calcium acetate. Then, the specimens were hydrothermally heated at a temperature of 220 °C for 4 h using an autoclave. The chemical composition of the surface layers was examined by XPS. The morphology of the surface was observed by SEM-EDS. The crystalline phases were identified by XRD. The corrosion resistance was determined by the electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 °C after various times of exposure in SBF. The oxide layers formed by PEO were porous, highly crystalline and enriched with Ca and P. After hydrothermal treatment, hydroxyapatite crystals precipitated on the surface. The results of electrochemical examinations show that the surface modification by PEO and hydrothermal treatment decreases the corrosion resistance of titanium.

Al 2 O 3 coatings were produced by the LPD method with the use of solid precursors of aluminium oxide. The coatings were deposited on non-heated substrates and on substrates heated from an external heat source at various geometries of the substrate/impulse plasma stream arrangement. Depending on the technological variant employed, the coatings obtained were composed of metastable or stable monotropic Al 2 O 3 phases. The process parameters also affected the morphology of the coatings. The IR, RS and XPS examinations of the atomic structure of the coatings, performed in the present study and in earlier investigations, have shown that the aluminium oxide coatings deposited from impulse plasma have a nanocrystalline amorphous structure. The phase composition and morphology of the coatings can be modified by heating the substrate in a stationary way during the IPD process, to a temperature of 500 K.

The influence of grains boundaries (GB) on the mechanical properties of polycrystals has been subject of extensive studies in the past and still attracts a great deal of attention. In the common approach, mechanical properties of polycrystals are referred to the distribution of so called coincidence grain boundaries (CSL boundaries). The aim of the present paper is to evaluate possible effect of the changes in the texture of a polycrystal on characteristics of the grain boundaries. Micrograined AISI type 316 austenitic stainless steel was used for this investigation. Specimens were annealed at 900 C and quenched in water. Mechanical test were carried out at a constant temperature of: 21, 450 and 700 C and at initial strain rate 1.67 {times} 10{sup {minus}4} s{sup {minus}1} up to uniform strain of 24%. Quantitative analysis was performed to characterize the initial texture and the textures after deformation at various temperatures. Conclusions were as follows: plastic deformation in tensile tests significantly changes crystal texture of polycrystals; changes in the texture induced by tensile deformation depend on the deformation temperature; the changes in the texture increase the number of special grain boundaries or more generally alter character of the grain boundaries.

The paper presents the results of examinations of the corrosion resistance of titanium after its being subjected to the surface modification by the alkali- and heat-treatments. The material examined was commercially pure titanium (grade 2). The samples were soaked in an aqueous 10M NaOH solution at 60 degrees C for 24 h and subsequently heated at 500, 600, or 700 degrees C for 1 h. The chemical composition of the surface layers was determined by X-ray photoelectron spectroscopy and secondary ion mass spectroscopy. The phases present in the layers were identified by XRD. The corrosion resistance was evaluated by electrochemical methods (Stern's method, potentiodynamic method, and impedance spectroscopy) at a temperature of 37 degrees C after short- and long-time exposures. The 13 h exposure was aimed to allow the corrosion potential to stabilize. The aim of the long-term exposures was to examine how the corrosion resistance of the modified samples changes during the exposure. Under the conditions prevailing during the experiments, the highest corrosion resistance was achieved with the samples heated at a temperature of 700 degrees C.

The effect of various ultrasonic fields on the yield and rate of three electrochemical processes of oxidation is ascertained. Some unexpected behaviour is reported, as well as definitive results.