Materials Science Forum Vol. 818

Abstract: The formation of a surface layer of diffused TiNiCo was carried out by metallization of fusible metal melt under isothermal conditions in an argon atmosphere at a temperature of 1100–1150 °C. The driving force of the process is the difference in concentration of alloying elements on the surface of the workpiece melt. A melt of lead or eutectic Pb-Bi was used as a transport medium, whose elements are in saturated atomic state and in direct contact with the surface of workpieces. This molten surface-activated product was purified from oxide films, providing a high wettability, which in turn provides good adhesion. Dissolved melt powders of Ti, Ni, and Co were first adsorbed on the surface of the items and then diffused into the surface of the volume. The cementation process was carried out cyclically by lifting the melt products every 25–30 minutes. The duration of the saturation process was 11–13 hours, depending on the desired coating thickness.

Abstract: The research work deals with the evaluation of limit states of machine needles failure where significant operational wear was anticipated. It focuses on the description of limit states, their causes and subsequent brittle fracture as a result of degradation. The experiment dealt with an evaluation of prepared microstructures followed by the fractography observation. Due to the fact that chemical composition of the material was not originally determined distribution of the chemical elements by linear and area method was performed within the experimental part. The work confirmed incorrect selection of the base material that although coated was typical by rapid degradation and failure which resulted in economic losses.

Abstract: The Zn-Mg coatings are considered as the next generation of steel covering to be used in automotive industry since they improve the corrosion resistance of the base material. The article is focused on the X-ray diffraction analysis of Zn-Mg coating in dependence on strain. The specimens made from a material, which has Zn-Mg coating, were gradually deformed until they became totally fractured. Subsequently, the specimens´ surface layer was analysed using X-ray diffraction. X-ray diffraction methods are used for evaluation of the qualitative changes in the real structure of the polycrystalline material. The modification of the real structure is considered as a degree of plastic deformation, change of crystallite size and their orientation depending on deformation.

Abstract: The paper deals with evaluation of relation between individual parameters of roughness of the blasted surfaces by the correlation analysis. Based on the measured values on the surfaces which were blasted by various types of blasting devices, the correlation matrix was set and the standard of statistic importance of correlation between the monitored parameters was determined from it. The correlation coefficient was also set.

Abstract: Numerous investigations have been performed in an attempt to improve fatigue strength of materials by creating compressive residual stresses in the surface layers as a result of the shot peening process. For example, during exploitation of the separating screener, some parts of screen sieve plate situated near the fixed edge undergo the largest deformation caused by impact bending and need special treatment. In this paper, the results of experimental tests are presented to analyse the effect of micro shot peening on surface layer characteristics and fatigue strength of steel sheet specimens. The effect of shot peening is more visible when fatigue life is taking into account. Thus, the use of shot peening of sheet surface made it possible to increase fatigue life of screener sieve.

Abstract: The paper deals with the application possibilities of new coatings types on the basis of Zn/Mg and their utilization at car-body production Comparison is done by evaluation bonded joints strength acc. to ISO 11339 for commonly used zinc-coated sheet at production car-body stampings (HDG Z100) with layer of new type on the basis of zinc/magnesium (ZM). Such utilization of new materials also means necessity to carry out test of the individual bonded car-body parts utility properties, mainly at peel loading, in dependence on adhesive type simultaneously with regard to the lubricant which is used in the technological process drawing of stampings and temperature under which is joint loaded. To guarantee required joints quality is one of the crucial criterions for applications new types of coatings in mass production.

Abstract: The requirements on tools used in the production of coins include high quality and reliability, dependent on the materials from which they are made, on manufacturing technology, heat treatment and final operations achieving functional area modification. Properties of the material of coins vary during their production and there is the so-called operational degradation that can be caused by an inappropriate technology of manufacturing. The quality of coining dies is expressed as their service life which ranges from approximately one hundred thousand to one million pieces of coins produced. Therefore, it is necessary to pay enough attention to the service life of coining dies. Surface treatment in the form of the application of hard PVD coatings is one of the ways of increasing the durability of coining die.In the present study, we analysed and tested three types of coatings deposited onto coining dies made of tool steel.

Abstract: The paper deals with the evaluation of coatings CoMoCrSi and WC-NiMoCrFeCo applied by High Velocity Oxygen Fuel technology from point of view of their suitability for renovation of sink roll in hot dip galvanizing line. The structure of the coatings was evaluated by metallographic analysis. The adhesion of the coatings as-sprayed and after thermal cyclic loading was determined by pull-off test. Wear resistance of the coatings was evaluated by pin-on-disc test in the corrosive environment of 1M aqueous solution of NaCl.

Abstract: The article deals with experimental results of fatigue life of plain carbon steel electrodeposited with nickel, chromium and iron-zinc coatings in the ultra-high-cycle region of loading (N = 6×10⁶ ÷ 10¹⁰ cycles) obtained at high-frequency fatigue testing (f ≈ 20 kHz, T = 20 ± 5 °C, R = -1). The results confirm continuous decrease of S-N curves after N = 10⁷ cycles. Electrodeposited coatings caused decrease of the fatigue life in the low and high-cycle fatigue region. In the ultra-high cycle region the influence of electrodeposited coatings on fatigue properties is negligible. There was observed no significant influence of thickness of electrodeposited coatings on fatigue lifetime decrease.