Five different alloy hardfacings on 16MnCr5 grade low-carbon ferritic–pearlitic steel were investigated in terms of their abrasive wear resistance in laboratory testing conditions. The selected hardfacing materials, namely “E520 RB”, “RD 571”, “LNM 420FM”, “E DUR 600”, and “Weartrode 62”, were individually deposited onto plain ground-finish surfaces of 10 mm thick steel plate samples. The studied hardfacings were fabricated using several different welding methods and process parameters proposed by their industrial manufacturers. In the present comparative study, the results obtained from laboratory abrasive wear tests of the investigated hardfacings were analyzed and discussed in relation to their microstructure, hardness, and wear mechanism characteristics. Regardless of great variety in microstructure and chemical composition of individual hardfacing materials, the results clearly indicated the governing factor for the wear resistance improvement to be the overall carbon content of the used hardfacing material. Thus it has been shown that the “E520 RB” hardfacing exhibited the highest abrasive wear resistance thanks to its appropriate hardness and beneficial “ledeburite-type” eutectic microstructure.
Nanocrystalline (nc) Cu powders with Al2O3 dispersoid (1-5 vol.% Al2O3) were prepared by combination of phase transformations with intensive milling and the following consolidation by pressing, sintering and hot extrusion. The electrical properties of the composites were analysed in relation to their microstructure and strength. The main contribution to the electrical resistivity was attributed to the grain/crystallite size of Cu matrix. The fraction of Fe impurities dissolved within the Cu matrix and the amount of Al2O3 particles in the Cu matrix affected the electrical resistivity remarkably. The optimal combination of electrical and strength properties can be achieved by cut-down of Al2O3 content and by optimization of dispersoid distribution in the matrix.K e y w o r d s : nanocrystalline Cu-Al2O3 alloys, dispersion strengthening, electrical properties, thermal stability
Dispersion strengthened materials are characterized by high strength properties and good temperature stability of structure until to temperatures of 0.9 melting temperature of aluminium. Dispersion strengthened Al -A1 4 C 3 materials are prepared by powder metallurgy way and the raw powder mixtures are generally consolidated by hot extrusion obtaining a fully dense material. This work is focused on a study of the microstructure in AI -A1 4 C 3 materials containing 4 and 12 vol. % A1 4 C 3 . The microstructure was analyzed by transmission electron microscopy and X-ray diffraction methods. The several microstructural features: morphology, size and distribution of particles of dispersoid, grain size and crystallite size of aluminium matrix, micro strain and dislocations density in materials were determined. The aim is an analysis of the effect of A1 4 C 3 amount on the microstructure formation during hot extrusion and analysis of the microstructure evolution at temperature loading and after cooling to ambient temperature.After hot extrusion the Al -12 vol. % A1 4 C 3 alloy is characterized by finer grains, higher micro strain and dislocations density and by a very low intensity of aluminium matrix deformation texture in comparison to Al -4 vol. % A1 4 C 3 material. In the hot extruded system with 4 vol. % A1 4 C 3 a strong deformation texture was observed. Therefore the amount of dispersoid strongly affects the formation of microstructures. The higher volume of A1 4 C 3 particles provides effective hindrance of the dislocations motion in Al matrix by the attractive interaction between dislocations and particles during extrusion. Both amounta of A1 4 C 3 dispersoid insure the thermal stability of microstructure of analyzed materials to 773 K.
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