Solid State Phenomena Vol. 225

Abstract: Hydrogen ingress into a metal has been observed at cavitation in distilled water and in 3% NaCl solution at open circuit potential. The measurements of hydrogen permeation rate have been made using an ultrasonic cavitation facility with an attached Devanathan-Stachurski double cell. Increase in vibration amplitude has been associated with the increase in amplitude of electrochemical voltage and current pulses and with the modification of hydrogen permeation rate. Hydrogen behavior within the metal has been affected by the cavitation induced dynamic stresses and metal deformation hardening, ascertained on the basis of the appearance of hydrogen permeation transients at cavitation in comparison with those recorded for the unstressed state. Metal damage has been a resultof associated effects of cavitation and hydrogen.

Abstract: Surface mechanical pulse treatment of medium-carbon low alloyed steels by high speed friction has been developed. Its major features are surfaces provided with the nanostructure with grain size of 20...50 nm, increased surface hardness and, correspondingly wear resistance. This nanostructure is subjected to the tempering temperature of 500 °С. Hydrogen charging of the strengthening materials decreases their plasticity, more considerably in steels with higher carbon content. However, it is possible to use mechanical pulse treatment to achieve high characteristics of strength, wear resistance and plasticity in hydrogen, selecting as-received matrix structure and the tempering temperature after surface treatment.

Abstract: Magnesium alloys are increasingly used in biomedical applications as temporary implants in the human body. The degradation behaviour of magnesium in physiological environments, in combination with the tendency of the corrosion products to be harmlessly dissolved and excreted with the urine, make magnesium very attractive for temporary implant applications. One of these applications is the use of the material for making coronary stents. Such applications are, on the other hand, critically dependent on the mechanical integrity of the implant during service. A number of recent studies have evaluated the in-vivo and in-vitro corrosion behaviour of magnesium and its alloys, and the ongoing research seeks to provide a fundamental understanding of the factors that influence their bio-degradation and environmental failure and to expand this understanding through experimental evidence. In this paper, the propensity of the magnesium alloys AM30 and WE43 to hydrogen embrittlement and to corrosion fatigue was studied using constant extension rate tensile tests on fatigue pre-cracked compact specimens and corrosion fatigue tests on tubes which are typically used for the production of stents and which were tested in simulated body fluid.

Abstract: In the present paper results of a microstructure examination of aluminum deformed by a two step process composed of a combination of two continuous straining methods – the KoBo extrusion and a cold rolling have been shown. The cold rolling was conducted in two variants – with an equal speed of both rolls (ESR) and with a differentiation of the upper ad the lower roll speed (a differential speed rolling – DSR). Results of a transmission electron microscopy (TEM) analysis revealed that applied processing strongly affects a microstructure of the examined material. It is shown that selected parameters of the KoBo extrusion allow obtaining a fine grained material with a grain size in the range of 1÷3 μm. Since a subsequent deformation of as KoBo extruded aluminum bars through the conventional rolling (ESR) leads to a formation of normally observed structural features (e.g. deformation bands), an application of the DSR methods results with a further grain refinement effect. It is found that, the KoBo extrusion combined with the DSR deformation allows obtaining aluminum plates that are characterized by a homogeneous structure with the grain size in the submicron range.

Abstract: Friction nodes in refrigeration compressors are lubricated with a mixture of lubricating oil and refrigerant. The concentration of refrigerant in oil depends on temperature and pressure of the refrigerant. Determining the effect of this mixture on the size of wear in refrigeration compressors in laboratory conditions is only possible through an accurate reflection of friction parameters.The authors managed to prepare a prototype stand for a tribological test with a model block-on-ring friction node and the high-pressure chamber allowing for simulated conditions in refrigeration compressors. The present paper includes the description of the experimental method and procedure of model wear test of refrigeration compressors parts. The study itself constitutes the basis for the verification tests of the stand.

Abstract: In recent years, substantial advancements have been made in the methodology of constructing material wear maps [1-3]. The maps make it possible to locate the dominating wear mechanisms in parameterized enforcement areas. The method constitutes a powerful tool for analyzing the mechanisms of material damage, the optimization of material choice and the conditions of use. Recently, the maps of corrosion and erosion wear as the function of the following parameterized enforcements have been made [3]:

Abstract: This paper presents an attempt to learn mechanical, corrosive and abrasive wear mechanisms and wear mechanisms in refrigerating compressor systems. The range of author’s examinations includes electrolytic liquids with abrasive material used in the food industry, especially in the sugar industry and lubricating oils polluted with refrigerant occurring in stationary and mobile refrigerating compressor systems. Tests on the wear mechanisms in complex service conditions show that the total wear occurring in tribological pairs due to simultaneous occurrence of destructive processes: frictional, corrosive and abrasive, is not a simple superposition of their individual effects occurring in conditions of their independent interactions. On the basis of carried out experiments with the use of mathematical methods for experimental designs, a statistical model describing the complex process of simultaneous wear was formulated. This model enables forecasting the wear and indicates that the abrasive wear is of dominating character. In the compressor refrigerating systems, the oil–refrigerant system is characterized by complex relations. Refrigerants andcompressor oils create compounds causing the accelerated wear of refrigerating compressors. The complex dependencies in case of the oil–refrigerant compound, cause that the lubricating and anti-wear properties are much worse than in case of pure oil. In case of exceeding their mutual miscibility, part of the agent is absorbed by oil. More stringent regulations concerning the protection of the ozone layer lead to the appearance of new agents creating new compounds with oils. In order to examine the influence of the compounds on the wear processes in the refrigerating compressors, we made a test stand. The stand is built of real elements of the refrigerating system consisting of, among others, a dismountable half-hermetic compressor. The stand, built for testing the model wear processes occurring in the refrigerating compressors, will be used for tribological tests in the atmosphere of refrigerants under regular loads conditions.The purpose of the performed examination is to develop methods of wear phenomena modelling in the complex service conditions in the sectors of food production and refrigerated storage .

Abstract: Cavitation erosion performance of modified macroscopic internal structure 316L stainless steel was investigated. The samples processed by means of SLM method were subjected to cavitation erosion test. The scanning electron microscope Philips 30/ESEM was used to examine morphology of eroded surface.

Abstract: In the paper the method and results are presented of the testing of tribological performance of a number of hard materials available commercially. The tests consisted in unidirectional sliding with liquid lubrication. The load and velocity regime chosen were similar to a standard four-ball lubricity test with constant velocity and load increasing over time. The regime was modified in such a way that over the initial part of the test both the velocity and load were linearly increased until a certain stable level of each input parameter was reached and the test was then continued till the termination due to chosen criteria. The materials used were high alloy tool steels and sintered carbides, normally used in working of metals by cutting. The lubricants environmentally inert or friendly fluids: water, mineral oil-in-water emulsion and vegetable oil. In the tests, typical sliding friction parameters were recorded, later evaluated on the basis of multiple parameters observable within the test such as e.g. maximum load and velocity reached, calculated maximum surface pressure or presence and amplitude of friction induced vibrations. In the group of material/material/lubricant combinations a ranking was created for each parameter in the assessment set by awarding points for performance. Best performance was granted the least amount of points. Overall performance was then judged by the accumulated number of points. The materials, which were evaluated as performing best have been chosen as input materials for the design and manufacture of a prototype motor for later laboratory and field testing.

Abstract: The paper presents research results of resistance to abrasive wear of titanium alloys: Ti6Al4V (commonly used) and Til3Nb13Zr (alloy of new generation) in association with polyethylene (UHMW-PE) predisposed for elements on pair of the knee endoprosthesis. The results were analysed from the point of possibility of an use of new generation titanium alloys as components of such implants. The tests of resistance to abrasive wear of selected kinematic pairs were conducted with the PT-3 tribometer in Ringer’s solution a constant load 2.0 kN, rotational speed of the rotating specimens (Ti13Nb13Zr and Ti6Al4V) 30 rev/min, and test duration 1 or 2 hrs.