Materials Engineering - Materiálové inžinierstvo (MEMI - E-Journal)
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Effects of Tribological Parameters on Slurry Erosion Behaviour of Uncoated and Coated Materials: A Review
Get PDFThis paper describes the pioneering work of various researchers in the field of slurry erosion behaviour of uncoated and coated materials in various industrial applications. The present study is focused on the slurry erosion behaviour of ash slurry disposal system of thermal power plants. The key components such as impeller and casing of ash slurry disposal pumps in thermal power plants experience this phenomenon of wear. Tribological parameters such as solid particle concentration, impact velocity of erodent on the target surface, impact angle, erodent particle size and shape, hardness of the striking particles and target material, etc. are responsible for slurry erosion. The research results show that the influence of tribological parameters on the slurry erosion is found to be significant and need to be evaluated and analyzed properly. The slurry erosion can be minimized by proper selection of materials and/or by providing the suitable protective coating on the material which can enhance the surface properties
Microstructure and properties of cast iron after laser surface hardening
Get PDFLaser surface hardening of cast iron is not trivial due to the material’s heterogeneity and coarse-grained microstructure, particularly in massive castings. Despite that, hardening of heavy moulds for automotive industry is in high demand. The present paper summarises the findings collected over several years of study of materials structure and surface properties. Phase transformations in the vicinity of graphite are described using examples from production of body parts in automotive industry. The description relates to formation of martensite and carbide-based phases, which leads to hardness values above 65 HRC and to excellent abrasion resistance
The study of molten zinc interaction on the surface of refractories in the production of zinc oxide
Get PDFThis paper is closely connected with the complete process of indirect production of ZnO as well as with the problems which occur during the metallurgical process. Purity of raw materials has an important influence on the final quality of ZnO and the occurrence of slag that remains stuck on the walls of furnace linings. ZnO is generally produced in the melting furnaces with different types of ceramic linings. Input materials have to be analyzed and investigated in the order to the predict behaviour from the aspect of the complex production process. Moreover, analysis of occurrence of undesirable phases in the batch, the output materials, character of furnace linings and waste material have to be evaluated and observed. Mutual interaction of all components will have a significant impact on the final quality of the ZnO. The result of the investigation of interaction occurring in the components will be used for the proposal of the suitable surface for furnace lining while the mentioned result is mainly obtained on the principle of chemical reactions and bonds. This surface for lining should have a minimum adhesion of the zinc and its alloys relating to production of ZnO
The effect of different shot peening intensities on fatigue life of AW 7075 aluminium alloy
Get PDFIn this study the effect of different shot peening intensities, from very light peening with ceramic beads to severe shot peening with high coverage, on the fatigue life of aircraft AW 7075 aluminium alloy was investigated. Results were discussed in means of surface roughness, character of deformed surface layer and residual stress profile measured by XRD methods. Light peening intensity creates high and shallow compression residual stress field in the subsurface layers of material and increases the fatigue life of studied alloy. Increasing the peening intensity increases the depth of residual stress field, however the surface damage created by impact of shots at high velocity causes significant surface damage and rapidly degrade the fatigue properties of AW 7075 aluminium alloy
Application of the S690QL class steels in responsible welded structures
Get PDFIn this paper are considered the most important properties of a special class of high strength steels S690QL, which can be classified into the group of special low alloyed steels. The high strength steels belong into a group of high quality steels. They possess exceptional mechanical properties, especially tensile strength and toughness. Those favorable properties are being achieved by application of special procedures of thermo-mechanical processing and simultaneous alloying with adequate elements. The advantages that the S690QL steels have with respect to other steels are being presented here. However, possibilities for application of those steels in responsible welded structures are limited due to their only relatively good weldability. The special procedures for improving it are discussed here, primarily preheating, controlled heat input during welding and additional heat treatment of the welded joint
Thermal stability of magnesium alloy AZ91 prepared by severe plastic deformation
Get PDFThis paper deals with the thermal stability of ultrafine-grained alloy AZ91 prepared by means of ECAP (Equal Channel Angular Pressing) method. Annealing experiments were conducted isochronally for 30 minutes in the temperature range of 220 to 400 °C in argon atmosphere. EBSD (Electron Backscatter Diffraction) method was used to image the changes in microstructure due to increased temperature
Study of calcium phosphate (DCPD) electrodeposition process on a Mg-3Al-1Zn magnesium alloy surface
Get PDFEvaluation of calcium phosphating process realized on Mg-3Al-1Zn alloy surface after grinding was investigated by electrochemical tests supported by photodocumentation. The electrodeposition treatment was performed by electrochemical method in water solution of Ca(NO3)2.4H2O, (NH4)2HPO4 and H2O2. The formation of calcium phosphate was divided into several stages and described using light microscopy. The progress in corrosion protection of created calcium phosphate layer in 0.9% NaCl after particular electrodeposition steps was evaluated by electrochemical impedance spectroscopy. The results in the form of Nyquist plots were analyzed using equivalent circuits
Structural Characteristics & Dielectric Properties of Tantalum Oxide Doped Barium Titanate Based Materials
Get PDFIn this research, the causal relationship between the dielectric properties and the structural characteristics of 0.5 & 1.0 mol% Ta2O5 doped BaTiO3 based ceramic materials were investigated under different sintering conditions. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant (k) as a function of temperature and frequency. Percent theoretical density (%TD) above 90% was achieved for 0.5 and 1.0 mol% Ta2O5 doped BaTiO3. It was observed that the grain size decreased markedly above a doping concentration of 0·5 mol% Ta2O5. Although fine grain size down to 200-300nm was attained, grain sizes in the range of 1-1.8µm showed the most alluring properties. The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant. Stable value of dielectric constant as high as 13000-14000 was found in the temperature range of 55 to 80°C, for 1.0 mol% Ta2O5 doped samples with corresponding shift of Curie point to ~82°C. Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics
INFLUENCE OF COOLING RATE DURING QUENCHING ON IMPACT TOUGHNESS OF A HOT-WORK TOOL STEEL AT AMBIENT TEMPERATURE AND AT 200 °C
Get PDFGross cracking of die-casting dies with inferior toughness sometimes occurs through too low preheating temperature and/or too slow cooling during quenching. This study aimed to clarify the influence of cooling rate on the toughness of the hot-work tool steel grade Uddeholm Vidar Superior at ambient temperature and at 200 °C, a typical preheating temperature for aluminium die-casting dies. Toughness was measured through instrumented Charpy V-notch impact testing. The decrease in energy absorption with increasing cooling time between 800°C and 500°C both at both ambient temperature and 200 °C was pronounced. At ambient temperature, the decrease in total energy was a consequence of a decrease in initiation energy whereas, at 200 °C, the decrease in total energy was due to a decrease in propagation energy
