Hydrogen embrittlement of low carbon structural steel

Hydrogen embrittlement (HE) of steels is extremely interesting topic in many industrial applications, while a predictive physical model still does not exist. A number of studies carried out in the world are unambiguous confirmation of that statement. Bearing in mind multiple effects of hydrogen in certain metals, the specific mechanism of hydrogen embrittlement is manifested, depending on the experimental conditions. In this paper structural, low carbon steel, for pressure purposes, grade 20- St.20 (GOST 1050-88) was investigated. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack and HE during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, hardness measurement, impact strength testing (on instrumented Charpy machine) and microstructural characterization by optical and scanning electron microscopy - SEM/EDX. Based on multi-scale special approach, applied in experimental investigations, the results, presented in this paper, indicate the simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. These results are consistent with some models proposed in literature, about a possible simultaneous action of the HELP and HEDE mechanisms in metallic materials

Winter wheat yield and quality depending on the level of nitrogen, phosphorus and potassium fertilization

Tests were carried out on stationary field trial, soil type vertisol in the process of degradation. The land on which the view is derived is characterized by low pH (pH lt 5.0). The Dose of nitrogen was 120 kg N/ha, which was administered in combination with phosphorous and potassium fertilizer. The tests showed a significant grain yield. Nitrogen had a most significant impact on the yield of wheat. The average grain yield of all treatments in the 2008/09 growing season was significantly greater than in the following years, mostly as the result of highly favourable weather conditions at major stages of plant development. The average highest yield was achieved in the variant N120P100K60 (5.528 t/ha), although the high yield of more than 5 t/ha was obtained and the triple treatments NPK where nitrogen is applied in the maximum amount of 120 kg/ha, 60 kg/ha P2O5 and 60 kg/ha K2O as well as variants NP in a quantity of 100 kg/ha P2O5 and 60 kg/ha K2O. Also, the 1000-grain weight was highest in balanced fertilization with all nutrients NPK (40 g), in a quantity of 120 kg N/ha, 100 kg/ha P2O5 and 60 kg/ha K2O. Averaged across years, significantly higher values for test weight were found in the control (76.91 kg/hl). Variance analysis showed statistically significant differences for grain yield and test weight between the vegetation seasons. Significant differences for 1000 grain weight between the variants of fertilization

POSSIBILITY OF WHEAT PRODUCTION IN AN INTEGRAL SYSTEM

The aim of this study was to determine the influence foliar application of the microbiological preparation (EM Aktiv) with a mixture of different groups of microorganisms (on different genotypes of wheat in sustainable agricultural production on the weight of 1000 grains and grain yield.) The research was conducted in the period 2016/2017-2018/2019 (factor A) in the region of Vojvodina, Serbia,  which  includes four varieties  of wheat (factor B). Factor C three variants of nitrogen are provided for wheat nutrition: 129, 106 and 83 kgˑha-1. During the vegetation, applications were performed with the microbiological preparation "EM Aktiv": F0 129 kgˑha-1 without EM, F1 129 kgˑha-1 + 1 x EM; F2 106 kgˑha-1 + 2 x EM; F3 83 kgˑha-1 + 3 x EM. At the end of the growing season, the weight of 1000 grains and the grain yield were measured. Factors A and  B had an effect on the increase of the tested traits p<0.01. The highest values were recorded in 2018/2019.  Factor C affected an increase in the weight of 1000 grains from 0.14% (F3) to 1.91% (F1). The differences in grain yield were significantly influenced by treatments (C) (p<0.05). The increase was from 1.91 % (F3) to 4.76 % (F1)

Stability of the expression of the maize productivity parameters by AMMI models and GGE-biplot analysis

The objective of this study was to estimate genotype by locality, by year, by treatments (G×LxYxT) interaction using AMMI model, to identify maize genotypes with stable number of rows of grains performance in different growing seasons. The trials conducted with seven maize lines/genotypes, four treatments, two years and at the two locations. The results showed that the influence of genotype (G), year (Y), locality (L), and G×L, G×T, G×L×T, G×Y×T, G×Y×L×T interaction on maize number of rows of grains were significant (p<0.01). The genotype share in the total phenotypic variance for the grains number rows of was 53.50%, and the interaction was 21.15%. The results also show that the sums of the squares of the first and second major components (PC1 and PC2) constitute 100% of the sum of the squares of the interaction G×L. The first PC1 axis belongs to all 100%, which points to the significance of the genotype in the total variation and significance of the genotype for overall interaction with other observed sources of variability. The highest stability in terms of expression of the grains number of rows had the genotype L-6, followed by the genotypes L-4, L-5 and L-3. The lowest stability was demonstrated by the genotypes L-2 and L-1, which confirmed that these genotypes are not important for further selection in terms of this trait

Impact of lime and NPK fertilizers on yield and quality of oats on pseudogley soil and their valorisation

In order to determine the effect of fertilization, environment, and their interactions on the yield and oats yield components. Five fertilization treatments (T1-control, T2-80 kg N ha(-1), T3-120 kg N ha(-1), 80 kg P2O5 ha(-1) and 80 kg K2O ha(-1), T4-N120P80K80 + 5 t ha(-1) of lime and T5-N120P80K80 + 5 t ha(-1) of lime + 30 t ha(-1) of farmyard manure) were examined during three growing seasons in Kraljevo location in Western Serbia. Grain yield (GY), 1000 grain weight (TGW), hectolitre weight (HW), plant height (PH), panicle length (PL), number of grains per panicle (NGP) and protein content (PC) were analysed. The aim of the study was to determine the effect of organic and mineral fertilization and calcification on the yield and oats yield components. On average, for all fertilizer variants, during the three-year trial, the highest yield of oats 3802 kg ha(-1) was obtained in the fertilizer variant with the combined application of NPK fertilizers, lime and manure. Positive highly significant correlation, during in the study trial were found between yields with PH, PL and NGP. Negative and highly significant dependencies were found between protein content with GY, PH and NGP. The results of these studies indicate the importance of rational introduction of adequate quantities of fertilization, calcification and humization in order to make oats as profitable as possible in the agro-ecological conditions in Pannonian Environments

Prediction and prevention of boiler tubing systems erosion in thermal plant

The problem of boiler tube erosion is a very complex problem and present in practically all fossil fuel power plants burning low heating value coals irrespective of their particular design and operating characteristics. Predicting the rate of material degradation processes due to operating conditions is the essential feature for assessing the remaining lifetime. This clearly includes the knowledge of the type and kinetics of erosion phenomenon. In order to follow the erosion process and provide a reliable prediction of erosion rate and thus tube time to failure, models taking into account all relevant effects have to be developed. In this paper the is presented results of testing carried out on the evaporator hopper tubes of 350MW unit exposed to erosion and were used to assess their remaining life

Hydrogen embrittlement of low carbon structural steel

Hydrogen embrittlement (HE) of steels is extremely interesting topic in many industrial applications, while a predictive physical model still does not exist. A number of studies carried out in the world are unambiguous confirmation of that statement. Bearing in mind multiple effects of hydrogen in certain metals, the specific mechanism of hydrogen embrittlement is manifested, depending on the experimental conditions. In this paper structural, low carbon steel, for pressure purposes, grade 20- St.20 (GOST 1050-88) was investigated. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack and HE during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, hardness measurement, impact strength testing (on instrumented Charpy machine) and microstructural characterization by optical and scanning electron microscopy - SEM/EDX. Based on multi-scale special approach, applied in experimental investigations, the results, presented in this paper, indicate the simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. These results are consistent with some models proposed in literature, about a possible simultaneous action of the HELP and HEDE mechanisms in metallic materials

Remaining life assessment of a high pressure turbine casing in creep and low cycle service regime

Thick walled components such as high pressure (HP) steam turbine casings operating under high parameter conditions are subjected to a complex stress state. As a result of that stress state, some parts of HP turbine casing undergo to the creep fatigue caused by the combination of thermal fatigue resulted from repeated start/stop operation and the creep which occurs during long-term operation at high temperature and high-pressure. It is well known that domestic thermal power plants have been in use over 100000 h which means that significant cost is required not only for maintenance, but often for renewal of equipment. Based on comprehensive investigation, the results of residual life assessment of one high pressure steam turbine casing, which belongs to the older turbine generation, taking into account simultaneous action of thermal fatigue and creep, are presented in this paper. Also, the critical flaw crack size of HP turbine casing is determined because this parameter has a strong influence on casing integrity and residual life. The results of residual life assessment provide not only a basis for further maintenance, but also estimated time for reparation or renewal

Impact of lime and NPK fertilizers on yield and quality of oats on pseudogley soil and their valorisation

In order to determine the effect of fertilization, environment, and their interactions on the yield and oats yield components. Five fertilization treatments (T1-control, T2-80 kg N ha-1, T3-120 kg N ha-1, 80 kg P2O5 ha-1 and 80 kg K2O ha-1, T4-N120P80K80 + 5 t ha-1 of lime and T5-N120P80K80 + 5 t ha-1 of lime + 30 t ha-1 of farmyard manure) were examined during three growing seasons in Kraljevo location in Western Serbia. Grain yield (GY), 1000 grain weight (TGW), hectolitre weight (HW), plant height (PH), panicle length (PL), number of grains per panicle (NGP) and protein content (PC) were analysed. The aim of the study was to determine the effect of organic and mineral fertilization and calcification on the yield and oats yield components. On average, for all fertilizer variants, during the three-year trial, the highest yield of oats 3802 kg ha-1 was obtained in the fertilizer variant with the combined application of NPK fertilizers, lime and manure. Positive highly significant correlation, during in the study trial were found between yields with PH, PL and NGP. Negative and highly significant dependencies were found between protein content with GY, PH and NGP. The results of these studies indicate the importance of rational introduction of adequate quantities of fertilization, calcification and humization in order to make oats as profitable as possible in the agro-ecological conditions in Pannonian Environments

Remaining life assessment of a high pressure turbine casing in creep and low cycle service regime

Thick walled components such as high pressure (HP) steam turbine casings operating under high parameter conditions are subjected to a complex stress state. As a result of that stress state, some parts of HP turbine casing undergo to the creep fatigue caused by the combination of thermal fatigue resulted from repeated start/stop operation and the creep which occurs during long-term operation at high temperature and high-pressure. It is well known that domestic thermal power plants have been in use over 100000 h which means that significant cost is required not only for maintenance, but often for renewal of equipment. Based on comprehensive investigation, the results of residual life assessment of one high pressure steam turbine casing, which belongs to the older turbine generation, taking into account simultaneous action of thermal fatigue and creep, are presented in this paper. Also, the critical flaw crack size of HP turbine casing is determined because this parameter has a strong influence on casing integrity and residual life. The results of residual life assessment provide not only a basis for further maintenance, but also estimated time for reparation or renewal