This article deals with studying the relationships among the chemical composition, microstructure and properties (hardness, micro-hardness, wear resistance) of powder additives based on NiCrBSi after their deposition. Tested materials reached a relatively wide range of hardness after deposition, which corresponds to their chemical composition and microstructure. The abrasive wear resistance of materials was tested on an emery cloth. The results indicate that both the hardness and abrasive wear resistance of tested materials depend especially on the content of carbon and chromium. Microstructural analysis indicates that the structure of tested materials is formed by the γ-Ni solid solution and intermediate phases based on boron, silicon and carbon. Those mostly form eutectics (three types), or are excluded by precipitation. There was also found a significant effect of chromium, but especially carbon content on the ratio between the solid solution and eutectics in the microstructure of tested materials. These different ratios of solid solution and eutectics were markedly reflected in micro-hardness behaviours in deposited layers. Micro-hardness values confirmed also the presence of carbidic particles in the layers with carbon content higher than 0.7 wt%.
The article evaluates the failure rate of devices in the Mechanical Processing Plant using a traditional quality tool, the Pareto-Lorenzo diagram. A comparative analysis of failure rates was performed, recorded in repair, inspection and maintenance card. Then, changes were proposed in order to reduce failure rates and earlier detection of equipment malfunctions. In order to analyze the failure rate of grain washer equipment during thick coal preparation process, one quality management tools was used - the Pareto-Lorenzo diagram. In this case, it is important to assess the mechanical failure of devices, and demonstrating which devices generate most repairs. Based on materials made available by the mine, such as: Repair, inspection and maintenance cards, Device cards, DTR documentation. Quantitative and qualitative assessment the most frequently occurring mechanical failures during operation of devices in process enrichment of coarse sizes was carried out. An attempt was made to assess failure rate of devices on a grain washer. A comparative analysis of failure rates in 2015-2017 recorded in the repair, inspection and maintenance card was carried out. Then, changes were proposed to stand, in order reduce failure rates, and earlier detection equipment malfunctions.
This article deals with possibilities of an application of controlled diffusion processes in remelting of steel surface layers with an electric arc of non-consumable electrode, in the environment enriched by boron, with the aim to achieve an improved wear resistance. In the design of experiment, there was formulated an assumption that the dissociation and ionisation of environment can be achieved, allowing the initiation of diffusion processes in the surface layer of the steel remelted. Conditions for creation of hard and stable structures with required properties should be obtained by enrichment of surface layers. The steel grades 16MnCr5 and X8CrNiTi1810 were used in experiments. Values of hardness and relative abrasive wear resistance were measured on samples after remelting. The metallographic analysis of remelted samples was performed as well. A significant increase in values of studied parameters was observed when remelting in the boron containing environment. The dependence applies to the effect of the environment on the change of properties and boron content in the remelting environment.
SPD (several plastic deformations) methods make it possible to obtain an ultrafine-grained structure (UFG) in larger volumes of material and thus improve its mechanical properties. The presented work focuses on the structural and mechanical changes of aluminium alloy AlMgSi0.5 (EN AW 6060) during processing by repeated extrusion through the ECAP rectangular channel. After a four-pass extrusion, the samples’ microstructures were observed using an optical microscope, where refinement of the material grains was confirmed. Tensile tests determined the extrusion forces and allowed interpretation of the changes in the mechanical properties of the stressed alloy. The grain size was refined from 28.90 μm to 4.63 μm. A significant improvement in the strength of the material (by 45%) and a significant deterioration in ductility (to 60%) immediately after the first extrusion was confirmed. The third pass through the die appeared to be optimal for the chosen deformation path, while after the fourth pass, micro-cracks appeared, significantly reducing the strength of the material. Based on the measurement results, new analytical equations were formulated to predict the magnitude or intensity of the volumetric and shape deformations of the structural grain size and, in particular, the adequate increase in the strength and yield point of the material.
The application of quick-setting adhesives based on cyanoacrylates is considerably spread in technical practice. The limit of these adhesives is the 'zero layer' of the adhesive. The advantage is in the speed of hardening process. A fast creation of bond, minimalizing of fixation means, and the possibility of fast manipulation with the adhesive bond are connected with that. The goal of the research is to describe the behaviour of quick-setting adhesives based on cyanoacrylates at different speed of deformation of adhesive bonds in the interval from 1 mm.min-1 to 48 mm.min-1. The change of adhesive bond strength, deformation and failure time were evaluated in experiments. A 3D model was set from experiment results by means of the least-square method.
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