AZ31D magnesium alloy is widely used in automotive, aircraft, and aerospace applications because of its high strength to weight ratio. However, the softness of the alloy results in higher wear rate and the high activity results in higher corrosion rate. With an aim of reducing the wear rate and corrosion rate of AZ31 alloy, surface composite of AZ31 alloy is fabricated by reinforcing niobium carbide (NbC) by friction stir processing. The microstructure and dispersion of the reinforcements in AZ31-NbC surface composite is analysed by optical microscopy. In addition, the microhardness and tribological characteristics of the developed AZ31-NbC surface composite are investigated. The results demonstrated an increase in microhardness (23.2 %) and the decrease in wear rate (15.6 % for a normal load of 2 kg) in the developed AZ31-NbC surface composite with respect to the base material. The immersion corrosion test was performed to analyse the corrosion rate of the developed AZ31-NbC surface composite in simulated sea water environment (3.5 wt % NaCl solution). The results indicate that the corrosion rate of the developed AZ31-NbC surface composite is higher than that of base material. A comprehensive analysis on the wear and corrosion mechanism of the developed AZ31-NbC surface composite is presented.
This research paper presents an analysis of the corrosion properties of steel-reinforced concrete samples during immersion in 3.5 wt. % NaCl aqueous solution by measuring their response both cathodic and anodic polarization in order to determine the corrosion rates in the function of their calcium nitrate inhibitor content. This cheap inorganic inhibitor was added to the concrete mix in concentrations of 1% and 3% by weight of cement in addition to two different superplasticizers (MapeiDynamon SR 31 and Oxydtron). The compressive strengths of the so prepared samples were also checked according to the relevant European standard and were within the acceptable limits, so this inhibitor does not weaken this important property of the concrete samples.
The test results on steel reinforced samples immersed in 3.5 wt. % NaCl aqueous solutions at room temperature showed promising corrosion mitigating effects just after 6 months testing period. After 6 months the lower corrosion currents (i.e. better corrosion resistance) for both types of superplasticizers were observed with those samples which contained 3% calcium nitrate inhibitor. The best result was observed with sample C4 (in this case 3% calcium nitrate was added to the mixture of cement+Oxydtron superplasticizer). The advantageous inhibition mechanism of nitrate anions is also discussed and interpreted.
To produce realistic test specimens with realistic flaws, it is necessary to develop appropriate procedure for corrosion flaw production. Tested specimens are made from steels commonly used in power plants, such as carbon steels, stainless steels and their dissimilar weldments. In this study, corrosion damage from NaCl water solution and NaCl water mist are compared. Specimens were tested with and without mechanical bending stress. The corrosion processes produced plane, pitting and galvanic corrosion. On dissimilar weldments galvanic corrosion was observed and resulted to the deepest corrosion damage. Deepest corrosion flaws were formed on welded samples. The corrosion rate was also affected by the solution flow in a contact with the specimens, which results in a corrosion-erosive wear. Produced flaws are suitable as natural crack initiators or as realistic corrosion flaws in test specimens.
The current trend in development of new metallic materials for certain types of implants is turning away from permanent, biologically inert materials to the use of biodegradable materials. Fe–Mn alloys represent high perspective material for development of new generation of temporary and biodegradable implants. The aim of this work was to study mechanical and corrosion characteristics of powder samples containing 25, 30 and 35 wt % of Mn which are fabricated by pressing, sintering, and additional spark plasma sintering. The influence of preparation method (pressing and sintering) to microstructure, phased composition and corrosion behavior of prepared alloys was studied.
Exposure of copper in corrosive environment is possible way, how to obtain artificial patina. Various solutions based on chloride, ammonia or polysulfide are commonly use in this purpose. Furthermore, it appears that the patina is also formed in an environment with an increased concentration of SO2 in the atmosphere. This procedure was tested in a small (30 l) exposure chamber, where the aggressiveness of the environment was monitored and where the effect of alternating the condensation and drying phases was shown to be positive. Based on this experiment, a 2 m3 pilot chamber was designed for which a water film sensor was developed and tested to ensure drying of the object surface. Monitoring of the aggressiveness of the environment showed that the pH and SO2 concentrations in the atmosphere are stable after approximately 5 hours and the ideal input SO2 concentration is 17.7 g m-3 at which the pH stabilizes at 2.7-3. By recording the voltage variation on the sensor, it was possible to monitor the formation and drying of the water film during the cycling of the condensation and drying phases.
This article presents the results of testing the sound pressure level and sound power level of the experimental 3PW-KPF1-24-40-2-776 high-pressure gear pump. Acoustic tests were conducted in an reverberation chamber. The results of the acoustic power tests indicate good acoustic parameters of the tested high-pressure unit.
This paper presents changes observed in the green areas in the city of Sopot. Analyses of Sopot archival materials, both cartographic and graphic, provided grounds for an assessment of changes and transformations in that respect starting from the 19th century. These analyses covered all the spa town protection zones A, B and C. This study also focuses on the aspect related with the primary function served by the spa town within the city. The city was also investigated in terms of the considerable cultural value frequently associated with green areas, since Sopot is an architectural gem of historical value. The analysis empasised the positive effect of green areas on the health resort character of the city. Green areas in the spa town of Sopot were analysed applying the comparative method. For this purpose maps and city maps were investigated. Additionally, the study is also based on archival graphic materials collected from the dawnysopot.pl website, as well as recent field studies (Świeczkowska, 2017).
This article presents the results of a durability test of a prototype low-pulsation pump. Hydraulic measurements conducted during the test enabled visualisation of the behaviour of the unit in working conditions. The test was conducted according to a strict factory standard, which states that pump performance parameters cannot decrease by more than 8% during durability testing. The material presented in this publication is the result of a study within the project entitled The development of innovative gear pumps with a reduced level of acoustic emission. The solution developed as part of the project has been successfully implemented for a series of gear pumps consisting of twenty-two units. Among other awards, the product won the Gold Medal at the 10th International Fair of Pneumatics, Hydraulics, Drives and Controls, Kielce 2017.
Selected districts of Valencia and the gradual transformation of their image are presented in this article. The formulation of an appropriate strategy of action and the effect of an example that were initiated by the construction of the City of Arts and Sciences have broken through the stagnation in thinking about space. Revitalisation efforts have been initiated in many of the city’s districts, as well as in its suburban zone. The great explosion of ideas and emotions also carried over to enhancing the historical traditions of the city and the holistic, multi-directional approach to the subject matter of renewal, providing the city with economic stimulation. The author’s own analyses presented in the article pertain to: Ciudad de las Artes y las Ciencias (City of Arts and Sciences), the new development of the Poblats Maritims coastal district, the Ciutat Fallera district and the Orba district of the town of Alfafar, located in Valencia’s metropolitan area. Various proposals for transforming the spatial structure of these districts point to the possibility of conducting an experimental hybrid policy intended to reconcile economic rescaling, entrepreneurship and cultural regionalism in the planned landscape.