Papers by Keyword: Erosion

Abstract: Cu/ZrB₂ composite was prepared by gas pressure infiltration of molten metal into ceramic preform. Microstructure and erosion resistance of composite was investigated. The microstructure was analysed by light microscopy and scanning electron microscopy. The chemical compositions were analysed using energy dispersive X-ray spectroscopy. Good penetration of copper along the grain boundaries of the 60% porosity sintered ceramics was analysed in the whole volume of composite. The interfacial morphology shows the regular interfaces without any macroscopic reactions [1]. Cu/ZrB₂ composite was subjected to 60 spark discharges to investigate the ablation resistance. Linear dependence of the amount of loss material on the number of electrical discharge analytical cycles for Cu/ZrB₂ composite was determined.

Abstract: The coastline is constantly in undergoing change, in terms of its position (retreat) and form. The retreat of coastal cliffs is a physical, dynamic and complex process that is controlled mainly by the geology of the area, strength properties of materials, marine conditions and climatic aspects of the region. This process is directly related to basal erosion, which is basically the mechanical destruction and/or removal of soil particles from the toe of coastal cliffs, caused mainly by wave action. Basal cliff erosion decreases the stability of the slope and may trigger mass movements and coast retreats. The coastal area of Rio Grande do Norte (Brazil) consists predominantly of sandy beaches and cliffs of Barreiras Formation. In this area, the human occupation has been increasing; therefore, it potentiates the probability of occurrence of mass movement. The objective of this study is to analyze the direct influence of basal erosion on stability of typical cliffs of the district of Tibau do Sul / Rio Grande do Norte - Brazil. The results showed that tensions are generated above the basal erosion as notch extension increases.

Abstract: Abrasive waterjet machining involves the impact of micro-particles at high or ultrahigh velocities. The material removal mechanism for ductile materials has been popularly accepted for over a half century as cutting wear and deformation wear caused by the component of impact force parallel and perpendicular to the target surface respectively. However, this definition of erosion mechanisms does not give an insight into the erosion process, but describes a surface phenomenon of the event. A computational study has been undertaken to reveal the underlying mechanisms of the material removal process. Based on the findings, the impact erosion mechanisms are re-defined as material destruction through (a) failures induced by inertia, (b) failure induced by elongation, and (c) failure induced by adiabatic shear bending. This new definition appears to better represent the physical process of material deformation and removal by loose micro-particle impacts at high and ultrahigh velocities.

Abstract: In this paper the effect of globular microstructure on the cavitation erosion resistance was assessed and compared to that of conventional dendritic one. Three different wrought aluminum alloys in as-cast conditions were investigated. The samples were completely characterized by metallographic analyses and microhardness measurements. Cavitation erosion tests were performed according to ASTM G 32 standard. The volume loss was evaluated during the test by periodical interruptions. It was identified the damaging mechanism in case of both dendritic and semisolid microstructure. It was also found that the globular microstructure increases the cavitation erosion resistance only for one of the studied alloys.

Abstract: Al₂O₃-SiCw (SiC whisker) powders were plasma sprayed on carbon steel under the electrostatic field. Effect of voltage on the microstructure and mechanical properties of the coatings was investigated. The erosion resistance was measured on the rotating disk erosion tester. The micro hardness and fracture toughness were obtained by the indentation method. It is found that the phase composition is unchanged for the coatings deposited in the presence or absence of electrostatic field while the grain size of coatings varies with the voltage. The porosity of coatings increases with the voltage slightly at first, and then a decrement tendency can be found. The erosion weight loss shows the similar trends with the porosity under the influence of voltage. The fracture toughness is the lowest when the voltage is 10 kV, and it is the highest for coatings deposited under no electrostatic field. The measurement of hardness yields the similar results though the voltage is different. The deflection behaviour of whiskers under the electrostatic field affects the deposition of molten powder and then the microstructure and properties of plasma sprayed coatings.

Abstract: In this paper, based on mass conservation, momentum conservation and turbulence k-ε model, the incompressible flow fluid dynamics model in sand discharging process is established. Computational Fluid Dynamics (CFD) technology is adopted to solve the flow field in the bend pipe and the erosion laws of the pipeline wall are predicted coupling material erosion model. Four erosion models of carbon steel material are adopted respectively to calculate the erosion laws and comparison is conducted. Further parametric study is carried out and different influence factors (such as pipeline structure, flow of fluid, et al.) to the erosion laws of the blooie line are discussed. The results indicate that the distribution characteristics of the erosion damage and the law of the erosion rate are changed with impact parameters in the bend pipe. There are obvious distribution differences of the erosion rate within a certain angle range obtained from different erosion models.

Abstract: The paper reports on the interaction of an electric discharge with solutions of organic substances in the electric reactor with iron loading. A colored water solution of organic substances with well-studied properties such as methylene blue (MB), furatsilin and eosin is used. The chosen organic substances allow to demonstrate the redox reactions, destruction of organic substances and their adsorption. It is found out that the process of direct interaction of organic substances with the discharge is 40%. Efficiency of sorption processes on iron load depends on the properties of the dissolved organic substances and for the MB is 21%, for furatsilin is 42% and for eosin is 63%. Post-effects have been observed after the action of the discharges and have shown activity for 24 hours. The obtained results allow modeling the mechanism of transformation of complex organic compounds e.g. humic substances or oil products.

Abstract: The coatings were obtained by high velocity oxy fuel method and their modification - new hybrid-spraying process. In this paper, the influence of manufacturing technology on structure and properties of coatings is presented. Examination of mechanical properties (microhardness) and selected results of tribological investigations of new material coatings are presented. The abrasion and erosion wear of materials were tested in ambient and elevated temperature. The article presents the results of structural studies of coatings too. Using a thickness gauge the rated uniformity of the applied coating, the thickness were determined. Microstructure, porosity, density of obtained coating was assessed using LM microscope. The obtained results confirm good erosion and abrasion properties of the tested coatings. Presented results indicate that the tested coatings may be used as a basic protection to wear condition in the energy industry.

Abstract: The aim of this study was to determine the effect of soaking on the erosion resistance of ZnAl22Cu3 alloy. The following samples were examined: as-cast, soaked at 185 °C and after solutionizing at a temperature of 385 °C. The scope of the examination included: Brinell hardness test, test of resistance to erosion and the examination of the surface of the samples after erosion tests. The examination showed a high resistance to erosion of ZnAl22Cu3 alloy. Heat treatment had no significant effect on the erosion resistance of the tested alloy. A significant impact on erosion resistance exerted the abrasive incidence angle. Consumption was greater when the angle of incidence was lower.

Abstract: One of the most effective methods for descaling hot-rolled steel products is performed using highpressure flat jet nozzles. These descaling nozzles are arranged in rows in hot rolling mills and areset in such a way that each adjoining pair of nozzles creates an overlapping area of water jet streams.Good homogeneity of the pressure distribution over the width of the hot-rolled plate is often used as anindicator of quality of the homogeneity of descaling. The presented laboratory measurements examineone pair of adjoining nozzles with a particular focus on the pressure distribution in the overlappingarea. This paper deals with one particular setting of a pair of descaling nozzles with zero offset anglesfor the jet streams. A measured pressure distribution and an outcome of an erosion test on an aluminumplate are presented and discussed. The erosion test shows that spots with higher pressures do notnecessarily result in a higher amount of removed material during an erosion test. The erosion test differs from the expected outcome in such a way that a detailed discussion of this phenomenon is outlined with possible explanations.