Forest stand decomposition of the Silesian Beskids which is followed by the tree cutting has been observed since the beginning of the 21st century. Changes in forest management due to the introduction of heavy machines for forest work mainly for skidding have been observed in the Silesian Beskids for the last decade. The paper presents results of a three-year investigation of erosion gullies forming in mountain forest after the skidding performed with use of heavy equipment. In the Wilczy Potok catchment comprising an area of above 100 ha 40 gullies were identified. The measurement of the length and depth of gullies showed that the total volume of soil and rock material removed from the catchment area due to erosion accelerated by skidding exceeded 9 000 m3. The year erosion rate for deep gullies was found to be 10%. The presented results show that necessary protective actions and preventive measures should be taken to mitigate the soil degradation processes.
The disposal of ash in a thermal plant through the slurry pipe is subjected to some erosion wear due to the abrasive characteristics of the slurry. A simulation study of particle-liquid erosion of mild steel pipe wall based on CFD-FLUENT that considers the solid-liquid, solid-solid and solid-wall interaction is presented in this work. The multi-phase Euler-Lagrange model with standard k-epsilon turbulence modeling is adopted to predict the particulate erosion wear caused by the flow of bottom ash-water suspension. Erosion rate for different particle size and concentration is evaluated at variable flow rate. It is observed that the pressure drop and erosion rate share direct relationships with flow velocity, particle size and concentration. The flow velocity is found to be the most influencing parameter. A model capable of predicting the erosion wear at variable operating conditions is presented. The simulation findings show good agreement with the published findings.
The paper presents the capabilities of welding techniques to creating properties of wear resistant high chromium cast iron alloy. The use of the right kind of welding sequence allows you to change the structure and properties of the obtained welds. Tests were conducted for one type of additive material in the form of self shielded core wire. In order to determine the effect of the type of welding sequence on the properties of welds performed welding using string bead and weave bead. The resulting weld was tested on hardness and research structure in an optical microscope. In the following studies have been made erosive tests wear of made hardfacing. String beads gave structure rich in carbides and harder about 270 HV of the weld with weave bead. Also, wear resistance was nearly twice as better for welds made with string beads. In the experiment a decisive role in the resistance to wear plays a high hardness of the deposit and the presence of carbides in its structure. Changes in the basic parameters of the deposition process allows for the formation of structure and properties of hardfacing welds in a wide range.
The sintered stainless steels of different microstructures (austenitic, ferritic and duplex) were laser surface alloyed with hard powders (SiC, Si3N4) and elemental alloying powders (Cr, FeCr, FeNi) to obtain a complex steel microstructure of improved properties. Laser surface alloying (LSA) involved different strategies of powder placing: the direct powder feeding to the molten metal pool and filling grooves machined on the sample surface by powder, and then laser surface melting. Obtained microstructures were characterised and summarised, basing on LOM, SEM and XRD analysis. The links between base material properties, like superficial hardness and microhardness, derived microstructures and erosion resistance was described. The LSA conditions and alloying powder placement strategies on erosion resistance was evaluated. The erosion wear is lower for Cr, FeCr, FeNi laser alloying, where powders were dissolved in the steel microstructure, and hard phases were not precipitated. Precipitations of hard phases (carbides, silicides, martensite formation) reduce erosion resistance of SiC alloyed stainless steel. The LSA with Si3N4 works better due to lack of precipitates and formation of a soft and ductile austenitic microstructure. The erosion wear at the impingement angle of 90° is high for hard and therefore brittle surface layers obtained as a result of alloying by hard particles (SiC, Si3N4). The softer and ductile austenitic stainless steel resist better than harder ferritic and duplex stainless steel material at studied erodent im pingement angle.
The paper deals with susceptibility of nodular cast iron with ferritic -pearlitic matrix on cavitation erosion . Cavitation tests were carried out with the use of a cavitation erosion vibratory apparatus employing a vibration exciter operated at frequency of 20 kHz. The study allowed to determine the sequence of subsequent stages in which microstr ucture of cast iron in superficial regions is subject to degradation. The first features to be damaged are graphite precipitates. The ferritic matrix of the alloy turned out to be definitely less resistant to cavitation erosion compared to the pearlitic matrix component.
To improve bioremediation of arsenic (As) contamination in soil, the use of microorganisms to efficiently reduce As and their assessment of genetic erosion by DNA damage using genomic template stability (GTS) evaluation and using RAPD markers were investigated. The five sites examined for microorganisms and contaminated soils were collected from affected gold mining areas. The highest As concentration in gold mining soil is 0.72 mg/kg. Microorganism strains isolated from the gold mining soil samples were tested for As removal capacity. Two bacterial isolates were identified by 16S rRNA gene sequence analysis and morphological characteristics as Brevibacillus reuszeri and Rhodococcus sp. The ability to treat As in nutrient agar (NA) at 1,600 mg/L and contaminated soil samples at 0.72 mg/kg was measured at 168 h, revealing more efficient As removal by B. reuszeri than Rhodococcus sp. (96.67% and 94.17%, respectively). Both species have the capacity to remove As, but B. reuszeri shows improved growth compared to the Rhodococcus sp. B. reuszeri might be suitable for adaptation and use in As treatment. The results are in agreement with their genetic erosion values, with B. reuszeri showing very little genetic erosion (12.46%) of culture in As concentrations as high as 1,600 mg/L, whereas 82.54% genetic erosion occurred in the Rhodococcus sp., suggesting that Rhodococcus sp. would not survive at this level of genetic erosion. Therefore, B. reuszeri has a high efficiency and can be used for soil As treatment, as it is capable to tolerate a concentration of 0.72 mg/kg and as high as 1,600 mg/L in NA.
This paper presents technological trials aimed at producing Ag-W, Ag-WC, Ag-W-C and Ag-WC-C composite contact materials and characterizing their properties. These materials were obtained using two methods, i.e. press-sinter-repress (PSR) at the refractory phase content of less than 30% by weight as well as press-sinter-infiltration (PSI) at the refractory phase content of ≥50% by weight). The results of research into both the physical and electrical properties of the outcome composites were shown. They include the analysis of the influence of the refractory phase content (W or WC) on arc erosion and contact resistance changes for the following current range: 6 kAmax in the case of composites with a low refractory phase content, 10 kAmax in the case of composites with the refractory phase content of ≥50% by weight.
Analysis of a crystallographic texture (a preferred orientation) effect on cavitation wear resistance of the as-cast CuZn10 alloy, has been conducted in the present paper. The experiment was conducted on the CuZn10 alloy samples with <101>//ND or <111>//ND preferred orientations (where the ND denotes direction that is perpendicular to the exposed surface). The cavitation resistance examinations have been carried out on three different laboratory stands (namely, vibration, jet-impact and flow stands) that are characterized by a various intensity and a way of cavitation’s excitement. Obtained results point towards a higher cavitation resistance of the CuZn10 alloy with the <111> // ND preferred orientation.