MATERIALS ENGINEERING, Vol. 20, 2013, No. 2
published on May 2013
CONTENTS and ABSTRACTS
Pastorek, F., Hadzima, B. (pp. 54-63)
STUDY OF CALCIUM PHOSPHATE (DCPD) ELECTRODEPOSITION PROCESS ON THE Mg-3Al-1Zn MAGNESIUM ALLOY SURFACE Full text (PDF 1039 kB) - Available online 24 February 2013
Evaluation of calcium phosphating process realized on the Mg-3Al-1Zn alloy surface after grinding was investigated by electrochemical tests supported by photodocumentation. The electrodeposition treatment was performed by electrochemical method in water solution of Ca(NO3)2.4H2O, (NH4)2HPO4 and H2O2. The formation of calcium phosphate was divided into several stages and described using light microscopy. The progress in corrosion protection of created calcium phosphate layer in 0.9% NaCl after particular electrodeposition steps was evaluated by electrochemical impedance spectroscopy. The results in the form of Nyquist plots were analyzed using equivalent circuits.
Krynke, M., Selejdak, J., Borkowski, S. (pp. 64-70)
DETERMINATION OF STATIC LIMITING LOAD CURVES FOR SLEWING BEARING WITH APPLICATION OF THE FINITE ELEMENT METHOD Full text (PDF 471 kB) - Available online 9 March 2013
In slewing bearings, a great number of contact pairs are present on the contact surfaces between the rolling elements and raceways of the bearing. Computations to determine the load of the individual rolling elements, taking into account the flexibility of the bearing ring, are most often carried out using the finite element method. Construction of a FEM full model of the bearing, taking into account the shape of the rolling elements and the determination of the contact problem for every rolling element, leads to a singularity of stiffness matrix, which in turn makes the problem impossible to solve. In FEM models the rolling elements are replaced by one-dimensional finite elements (linear elements) to simplify the computation procedure and to obtain an optimal time for computations. The methods of modelling the rolling elements in the slewing bearing, in which balls have been replaced by truss elements with a material non-linear characteristic located between the raceway centres of the curvatures in their axial section, are presented in the paper.
Krajňák,T., Máthis, K. (pp. 71-76)
EVOLUTION OF MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ULTRA-FINE-GRAINED INTERSTITIAL-FREE STEEL PROCESSED BY EQUAL CHANNEL ANGULAR PRESSING Full text (PDF 1038 kB) - Available online 15 April 2013
Equal channel angular pressing (ECAP) is one of the severe plastic deformation techniques which is widely used for producing metals with ultra-?ne-grained microstructures. In the present work the influence of number of pressing by route BC on grain size, evolution of microstructure and mechanical properties of interstitial-free (IF) steel has been investigated by means of optical microscopy, electron back-scattering diffraction (EBSD) and tensile tests. It has been found, that the grain size decreases with increasing number of passes. Simultaneously tensile strength increases. The thermal stability of ECAP-processed microstructures has been also examined. It was found that the degradation of mechanical properties occurs only above 600 °C and 700 °C.
Novák, P., Michalcová, A., Voděrová, M., Marek, I., Vojtěch, D. (pp. 77-82)
THERMAL STABILITY OF Al-Cu-Fe QUASICRYSTALS PREPARED BY SHS METHOD Full text (PDF 843 kB) - Available online 15 April 2013
Quasicrystal-containing materials are usually prepared by rapid solidification of the melt (e.g. by melt spinning) or mechanical alloying. In this work, the method using exothermic reactions between compressed metallic powders called SHS (Self-propagating High-temperature Synthesis) was tested. The microstructure and phase composition of the product was described in dependence on cooling regime from the reaction temperature. Thermal stability of prepared Al-Cu-Fe quasicrystals was studied by annealing at the temperatures of 300 and 500 °C.
Jurči, P. (pp. 83-90)
TRIBOLOGICAL PROPERTIES OF CrAgN THIN FILMS Full text (PDF 965 kB) - Available online 30 April 2013
CrN and CrAgN thin films were magnetron sputtered onto the substrate made from Vanadis 6 cold work tool steel. The films were examined on tribological properties using a high temperature Pin-on-disc tribometer. Obtained results show that there is almost no effect of Ag addition on the friction coefficient when tested at a room temperature against alumina. The testing against the same counterpart at higher temperature gave positive effect of the silver addition on the friction coefficient. The testing against 100Cr6 ball bearing steel gave higher friction coefficient than that against alumina while the testing against CuSn6-bronze led to much lower µ. When tested at a room temperature, the wear performance of the films was positively affected only in the case of the CrAg3N film developed at 500 °C. On the other hand, addition of 3 wt% Ag into the CrN increased the wear performance at elevated temperatures while the addition of 15 wt% Ag has made the film too soft and sensitive to wear.
Luptáková, N., Anisimov, E., Janotová, I., Švec, P,, Pešlová, F. (pp. 91-97)
THE STUDY OF MOLTEN ZINC INTERACTION ON THE SURFACE OF REFRACTORIES IN THE PRODUCTION OF ZINC OXIDE Full text (PDF 536 kB) - Available online 30 April 2013
This paper is closely connected with the complete process of indirect production of ZnO as well as with the problems which occur during the metallurgical process. Purity of raw materials has an important influence on the final quality of ZnO and the occurrence of slag that remains stuck on the walls of furnace linings. ZnO is generally produced in the melting furnaces with different types of ceramic linings. Input materials have to be analyzed and investigated in the order to the predict behavior from the aspect of the complex production process. Moreover, analysis of occurrence of undesirable phases in the batch, the output materials, character of furnace linings and waste material have to be evaluated and observed. Mutual interaction of all components will have a significant impact on the final quality of the ZnO. The result of the investigation of interaction occurring in the components will be used for the proposal of the suitable surface for furnace lining while the mentioned result is mainly obtained on the principle of chemical reactions and bonds. This surface for lining should have a minimum adhesion of the zinc and its alloys relating to production of ZnO.
© University of Žilina, Faculty of Mechanical Engineering, ISSN 1335-0803