MATERIALS ENGINEERING, Vol. 18, 2011, No. 4
published on December 2011
CONTENTS and ABSTRACTS
Zatkalíková, V, Liptáková, T. (pp. 115-120)
PITTING CORROSION OF STAINLESS STEEL AT THE VARIOUS SURFACE TREATMENT Full text (PDF 2820 kB) - Available online 27 September 2011
The stainless steel surface treatment is very important with regard to its pitting corrosion susceptibility. An effect of various types surfacing on pitting corrosion resistance of AISI 304stainless steel is investigated in this work. The samples of the tested material are turned, blasted, peened, grinded and a half of them are pickled to achieve higher purity of surfaces and better quality of passive film. Eight types of different finished surfaces are tested by electrochemical and immersion tests to determine corrosion behaviour in conditions where pitting is evoked by controlled potential and second by solution with high redox potential. By this way the effect of mechanical and chemical surface treatment on the resistance to pitting corrosion, character, size and shape of pits are compared in the conditions of different mechanisms of corrosion process.
Belan, J. (pp. 121-128)
QUANTITATIVE METALOGRAPHY OF HEAT TREATED ŽS6K SUPERALLOY Full text (PDF 1364 kB) - Available online 28 September 2011
Alloy ŽS6K is former USSR superalloy used in DV – 2 jet engine. It is used for turbine rotor blade and whole cast small sized rotors with working temperature up to 800 ÷ 1050°C. This alloy was evaluated after annealing at 800 °C/ 10 and followed by cooling with various rate, presented with cooling in water, oil and air. Cooling rates, represented by various cooling mediums, have a significant influence on diffusion processes, which are going in structure. Methods of quantitative metallography (Image Analyzer software NIS – Elements for carbides evaluation, measuring of secondary dendrite arm spacing and coherent testing grid for gama' - phase evaluation) are used for evaluation of structural characteristics on experimental material – Ni base superalloy ŽS6K.
Šohaj, P. (pp. 129-133)
EVALUATION OF MICROSTRUCTURAL STABILITY OF DISSIMILAR WELD JOINTS Full text (PDF 5879 kB) - Available online 28 September 2011
The microstructural changes occurring in the weld joint P92/316Ti during his long-term exposure at high temperature were studied. In parallel to experiments were carried out calculations of phase equilibria for the base materials and the weld joint using the ThermoCalc software. Based on the experimental results and computational modeling results were evaluated a microstructural stability and the application of the base materials and the weld joint.
Kohout, J. (pp. 134-139)
KINETICS OF HARDNESS CHANGES DURING AGE-HARDENING OF SILUMIN Full text (PDF 119 kB) - Available online 19 October 2011
Simple phenomenological description of age-hardening kinetics of supersaturated solid solution is presented using the sum of exponential functions with negative arguments containing rate constants, for whose temperature dependence the Arrhenius equation is used. The number of exponentials in the sum is discussed considering sufficiently accurate description as well as the number of distinguishable processes occurred during hardening. Also the limits of this approach are presented. Hardness changes of silumin during age-hardening are used for demonstration of this procedure.
Dodek, A., Fajnor, P., Liptáková, T., Zatkalíková, V., Anisimov, E., Vojsovičová, M. (pp. 135-140)
CORROSION OF COPPER PIPES JOINTS IN SIMULATED OPERATING CONDITIONS Full text (PDF 1086 kB) - Available online 23 October 2011
Joining of copper pipes used for liquid media transport are made as demountable and fixation joints. This work deals with corrosion behavior of the joints made by soft soldering, hard soldering and fitting. Corrosion properties of the joints were studied after 11 month exposition in conditions simulated the operating environment. The experiment was made in the 3% NaCl solution, at temperature 20° C for 16 hours and at 80° C for 8 hours per day, the solution was flowing 8 hours by the average rate 0,27 m.s-1. Evaluation of the joints corrosion attacks was made visually, by light and electron microscopy with chemical analyses of corrosion products.
Blažek, D., Palček, P. (pp. 145-150)
INTERNAL FRICTION USE IN MONITORING THE DEGRADATION PROCESSES IN A MATERIAL Full text (PDF 1112 kB) - Available online 24 October 2011
During the measurement of the fatigue life of material, the specimen undergoes large number of stress cycles. While the observed number of cycles before failure is considered to be the most important result (often the only one), more knowledge can be obtained. Measuring energy consumption of specimen during the cycling, the changes of microstructure of material (especially dislocation structure and crack initialization) can be traced. The evolution of dynamic modulus can be watched on the same equipment. These information becomes very important, especially in the research of gigacycle fatigue strength and fatigue limit below which the continued loading does not lead to structural failure. In this article some remarks on microstructural changes in materials, which can be monitored by nondestructive measurement of internal friction are presented.
Nerádová, M., Augustín, R., Kovačócy, P. (pp. 151-154)
THE EFFECT OF THE ANNEALING TEMPERATURE ON THE CORROSION RESISTANCE OF WELD JOINT OF AISI 310 STEEL - SHORT COMMUNICATION Full text (PDF 1466 kB) - Available online 26 October 2011
The article presents samples of weld joint of AISI 310 austenitic steel which were subjected to solution annealing at various temperature - time exposures. The objective of the experiment was to determine the annealing temperature so that the steel should not be sensitized. Tendency to intercrystalline corrosion was analysed by means of a corrosion test in 10 % oxalic acid according to ASTM A 262. At the temperatures of 1000 and 1100°C held for 15 min. the steel was not sensitized. At the temperature of 850°C the steel was sensitized, i.e. susceptible to intercrystalline corrosion.
Gaško, M., Rosenberg, G. (pp. 155-159)
CORRELATION BETWEEN HARDNESS AND TENSILE PROPERTIES IN ULTRA-HIGH STRENGTH DUAL PHASE STEELS – SHORT COMMUNICATION Full text (PDF 129 kB) - Available online 3 November 2011
The possibility to predict yield strength, strength limit, fatigue live estimation as well as other mechanical properties depending on values of materials hardness is commonly known and it is often used in practice. The main aim of this contribution is to review the possibilities of application of correlation relationships between hardness and ultimate tensile strength of steel sheets in various structural states. The experiments were performed on advanced steels with structure which is composed from ferrite and martensite (dual phase steels).
© University of Žilina, Faculty of Mechanical Engineering, ISSN 1335-0803