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Purpose: This paper is devoted the investigation hydrogen influence on of wear resistance of high nitrogen steel (HNS) at dry and solid state lubricants assistant friction. It has been established that after hydrogenation at 250 N loading the wear rate increased by 2.9 ... 4.1 times. Microhardness of hydrogenated layer was 7.6 ... 8.2 GPa, that is increased after hydrogenation in two times. After adding the (GaSe)xIn1-x compounds to the tribo conjugates by X-ray diffraction analysis it has been established the appearance of new phases which formed during the friction process and detected on the friction surface. Design/methodology/approach: This work presents research results concerning the comparative tests of high nitrogen steels in the circumstances of dry rolling friction. It was conducted the experiments to determine the tribological properties of high-nitrogen steels under rolling friction. The test pieces were manufactured in the form of rollers, and rotated with a linear velocity 2.27 m/s (upper roller), 3.08 m/s (bottom roller). Upper roller is made from HNS was subjected for hydrogenation. Analysis of friction surfaces indicates the complex mechanism of fracture surfaces. The results of the local X-ray analysis and X-ray diffraction analysis has been established the appearance of new phases and elements on the friction surface. Findings: It has been found that the level of wear resistance of the investigated materials under hydrogenation. Compounds realize chemisorption, tribochemical mechanisms of the formation of thin protective (anti-wear, antifriction) layers on metal surfaces. Research limitations/implications: An essential problem is the verification of the results obtained using the standard mechanical tests, computer-based image analysis and other methods. Practical implications: The observed phenomena can be regarded as the basic explanation of reduces the plasticity characteristics after hydrogenation. Applying the (GaSe)xIn1-x compounds as a lubricant will allow the formation of films on friction surfaces that can minimize surface wear, which will contribute to the transition to a wear-free friction mode. The protective film is a barrier to high shear and normal loads, preserving the base metal of the part and providing reduced wear and friction. Originality/value: The value of this work is that conducted experiments permit to determine the tribological properties of high nitrogen steels under rolling friction after hydrogenation. After adding (GaSe)xIn1-x compounds to the tribo conjugates after due to X-ray diffraction analysis it has been established the appearance of new phases which formed during the friction process and detected on the friction surface. [ABSTRACT FROM AUTHOR]

In this research, the laser rapid manufacturing (LRM) additive manufacturing process was used to deposit multifunctional hydroxyapatite (HAP) coatings on high nitrogen stainless steel. LRM overcomes the limitations of conventional coating processes by producing coatings with metallurgical bond, osseointegration, and infection inhibition properties. The microstructure, microhardness, antibacterial efficacy, and bioactivity of the coatings were investigated. The microstructure studies established that the coatings consist of austenite dendrites with HAP and some reaction products primarily occurring in the inter-dendritic regions. A Vickers microhardness test confirmed the hardness values of deposited HAP coatings to be higher than those of the bare 254SS samples, while a fluorescence activated cell sorting test confirmed their superior antibacterial properties as compared with pristine samples. The coated samples immersed in simulated body fluid showed rapid apatite forming ability. The results obtained in this research signify the potential application of the LRM process in synthesizing multifunctional orthopaedic coatings. [ABSTRACT FROM AUTHOR]

Plasma nitriding treatment was applied at 603 K to introduce interstitial nitrogen into carbon steel and to form a precipitation free nitrogen solid solution layer. The nitrogen solid solution layer contained 0.05-0.1 mass% (0.2-0.4 at%) interstitial nitrogen and resulted in ca. 0.7% expansion of the lattice parameter. Anodic polarization measurements of the nitrogen solid solution layer were taken to reveal the effect of interstitial nitrogen on the polarization behavior of carbon steel. The nitrogen solid solution layer was passivated in Na2SO4 solutions above pH 6.0. The effectiveness of alkalization and NO3- ions, which were the expected dissolution by-products or products of interstitial nitrogen, was confirmed using buffer solutions at pH 6.0 and 8.45 with and without NO3-ions. In addition, the work function of carbon steel increased 0.08 eV with the interstitial nitrogen, suggesting the interstitial nitrogen made it difficult for the carbon steel to dissolve into solutions. Therefore, it was concluded not only did the interstitial nitrogen affect the exposed environments due to the alkalization and NO3- ions, but also that the work function of the carbon steel changed. The combination of these three factors resulted in the passivation of the nitrogen solid solution layer in a neutral environment. [ABSTRACT FROM AUTHOR]

Comparative studies are provided for cryogenic austenitic steels. All of the steels studied may be used as cryogenic materials with increased strength. A new economic low-nickel steel Cr19Ni6Mn10Mo2N has the highest strength level in hot-rolled and cold-rolled conditions from the austenitic condition region, and this provides effective use within the Arctic and Antarctic climatic regions. This steel has a stable austenitic structure and quite good mechanical properties from +100 to -170°C and at these temperatures may replace highly alloyed steel type Cr22Ni16Mn7N. Traditional steel Cr19Ni9N may only be used as cryogenic material for undeformable objects since below 70°C strain-induced martensite may form within it. [ABSTRACT FROM AUTHOR]

This article presents some results obtained during the first stage of the European Union project titled "STEELWIND," a part of which has been dedicated to roller-race contact dynamics. Contact has been modeled qualitatively using viscous-elastic friction, in the sliding regions, and hysteresis-modified Hertzian pressure in the whole contact zone. Slip and stick areas are detected within the contact area where the sliding velocity may have both opposite directions parallel to the entraining velocity. Considering the complexity of the hybrid rolling-sliding-sticking conditions, the developed model, although simplified, can be helpful to develop a sliding-rolling test by means of a standard reciprocator stand, where nonsymmetrical and mobile configurations of the testing race samples are introduced. [ABSTRACT FROM AUTHOR]

Corrosion tests are performed on developed chromium corrosion-resistant steels alloyed with nitrogen. A set of tests shows that depending on chemical composition and production parameters the corrosion resistance indices for steels of one class may differ by an order of magnitude. Revelation of a dependence makes it possible to conclude that an increase within steel of nitrogen and molybdenum content combined with quenching and low-temperature tempering at 400°C makes it possible to prepare steel with good pitting corrosion resistance in aqueous media, particularly, under sea water conditions. [ABSTRACT FROM AUTHOR]

In this study, the influence of cyclic strain amplitude on the evolution of cyclic stress-strain response and the associated cyclic deformation mechanisms in 316LN stainless steel with varying nitrogen content (0.07 to 0.22 wt pct) is reported in the temperature range 773 K to 873 K (500 °C to 600 °C). Two mechanisms, namely dynamic strain aging and secondary cyclic hardening, are found to strongly influence the cyclic stress response. Deformation substructures associated with both the mechanisms showed planar mode of deformation. These mechanisms are observed to be operative over certain combinations of temperature and strain amplitude. For strain amplitudes >0.6 pct, wavy or mixed mode of deformation is noticed to suppress both the mechanisms. Cyclic stress-strain curves revealed both single and dual-slope behavior depending on the test temperature. Increase in nitrogen content is found to increase the tendency toward planar mode of deformation, while increase in strain amplitude leads to transition from planar slip bands to dislocation cell/wall structure formation, irrespective of the nitrogen content in 316LN stainless steel. [ABSTRACT FROM AUTHOR]

Influence of nitrogen content on low cycle fatigue life and fracture behavior of 316LN stainless steel (SS) alloyed with 0.07 to 0.22 wt pct nitrogen is presented in this paper over a range of total strain amplitudes ( ±0.25 to 1.0 pct) in the temperature range from 773 K to 873 K (500 °C to 600 °C). The combined effect of nitrogen and strain amplitude on fatigue life is observed to be complex i.e., fatigue life either decreases/increases with increase in nitrogen content or saturates/peaks at 0.14 wt pct N depending on strain amplitude and temperature. Coffin-Manson plots (CMPs) revealed both single-slope and dual-slope strain-life curves depending on the test temperature and nitrogen content. 316LN SS containing 0.07 and 0.22 wt pct N showed nearly single-slope CMP at all test temperatures, while 316LN SS with 0.11 and 0.14 wt pct N exhibited marked dual-slope behavior at 773 K (500 °C) that changes to single-slope behavior at 873 K (600 °C). The changes in slope of CMP are found to be in good correlation with deformation substructural changes. [ABSTRACT FROM AUTHOR]

Low nitrogen content in liquid steel is required for most of the steelmaking companies, where vacuum degassing of liquid steel is usually carried out to remove nitrogen as well as other impurity elements during ladle treatment. This paper presents an integrated computational fluid dynamics (CFD) model for simulating the nitrogen removal in an industrial vacuum tank degasser (VTD). In the CFD model, oxygen and sulfur are considered as surface-active elements decreasing the denitrogenation rate at the gas-steel interface. An activity coefficient and a desulfurization sub-model are implemented to compute the effective activity coefficients of the related elements and the evolution of sulfur content in liquid steel during the process, respectively. The effect of various elements on denitrogenation rate in the VTD is studied with the developed model. For the used steel compositions the denitrogenation rate decreases with an increase in the content of [S], [O], [Cr], [Nb], [V], [Ti], or [Mn], whereas it increases with an increase in the content of [C], [Si], [P], [Ni], or [Al]. The model is validated by comparing final nitrogen contents measured from the industrial plant with the ones predicted by the model and good agreements were found. The model has proven to be a useful and accurate tool for predicting final nitrogen content of liquid steel in the plant. [ABSTRACT FROM AUTHOR]

The effect of nitrogen content on the dynamic strain ageing (DSA) behaviour of type 316LN austenitic stainless steel has been studied. The nitrogen content was varied from 0·07 to 0·22 wt-%. The tensile tests were carried out over a temperature range of 300-1123 K and at three strain rates in the range 3×10−3-3×10−5 s−1. Serration was observed in the load elongation curves in the intermediate test temperature range and has been considered due to DSA phenomenon. The critical strain to onset of serrated flow increased with increase in nitrogen content and strain rate. The temperature for onset of DSA and the temperature of disappearance of DSA were found to increase with the increase in nitrogen content. The variations in tensile strength and work hardening rate of the steel with temperature exhibit peak values in the intermediate temperature range and have been attributed due to DSA phenomenon. The activation energy for DSA, estimated based on the temperature and strain rate dependences of the strain to onset of serrated flow, was found to increase from 111 to 218 kJ mol−1 with the increase in nitrogen content from 0·07 to 0·22 wt-% and the increase has been attributed to the possible enhanced interaction of the DSA causing interstitial nitrogen with substitutional chromium. [ABSTRACT FROM AUTHOR]

An investigation of the nitrogen pickup of liquid steel from ladle slag after vacuum degassing was made. Nitride capacities, CN, of a number of ladle slags were determined at controlled nitrogen and oxygen potentials at 1873 K. The nitride capacities in the composition range studied were found to be very low. In accordance with the literature, the nitride capacity was found to increase with increasing SiO2 content. Industrial trials were performed. The nitrogen content of the steel was determined before and after vacuum degassing as well as after the waiting period. Three different trends of the variation of nitrogen content in the steel were observed. Both the laboratory study and the industrial trials revealed that the transfer of nitrogen from slag to steel was not the reason for nitrogen pickup in the steel subsequent to vacuum degassing. [ABSTRACT FROM AUTHOR]

Effects of cold rolling deformation on the microstructure, hardness, and creep behavior of high nitrogen austenitic stainless steel (HNASS) are investigated. Microstructure characterization shows that 70% cold rolling deformation results in significant refinement of the microstructure of this steel, with its average twin thickness reducing from 6.4 μm to 14 nm. Nanoindentation tests at different strain rates demonstrate that the hardness of the steel with nano-scale twins (nt-HNASS) is about 2 times as high as that of steel with micro-scale twins (mt-HNASS). The hardness of nt-HNASS exhibits a pronounced strain rate dependence with a strain rate sensitivity (m value) of 0.0319, which is far higher than that of mt-HNASS (m = 0.0029). nt-HNASS shows more significant load plateaus and a higher creep rate than mt-HNASS. Analysis reveals that higher hardness and larger m value of nt-HNASS arise from stronger strain hardening role, which is caused by the higher storage rate of dislocations and the interactions between dislocations and high density twins. The more significant load plateaus and higher creep rates of nt-HNASS are due to the rapid relaxation of the dislocation structures generated during loading. [ABSTRACT FROM AUTHOR]

The microstructure and the kinetics of growth of the nitrided zone of a Mo-containing maraging steel were investigated by performing gaseous nitriding at temperatures between 713 K (440 °C) and 793 K (520 °C) and at nitriding potentials up to 0.5 atm for both solution-annealed and precipitation-hardened specimens. The microstructure of the nitrided zone was investigated by means of X-ray diffraction (phase constitution; crystal imperfection). Fine, initially largely coherent MoN-type precipitates developed in the nitrided zone. The elemental concentration-depth profiles were determined employing glow discharge optical emission spectroscopy (GDOES). The nitrogen content within the nitrided zone exceeds the nitrogen content expected on the basis of the molybdenum content and the equilibrium solubility of nitrogen in a (stress-free) ferritic matrix: excess nitrogen occurs. A numerical model was applied to predict the nitrogen concentration-depth profile within the nitrided layer. The model describes the dependence on time and temperature of the nitrogen concentration-depth profiles with, as fit parameters, the surface nitrogen concentration, the diffusion coefficient of nitrogen in the matrix, a composition parameter of the formed nitride and the solubility product of the nitride-forming element and dissolved nitrogen in the matrix. Initial values for the surface nitrogen concentration and the composition parameter were determined experimentally with an absorption isotherm and fitted to the measured nitrogen concentration-depth profiles. The results obtained revealed the striking effects of the amount of excess nitrogen and the extent of precipitation hardening on the developing nitrogen concentration-depth profile. [ABSTRACT FROM AUTHOR]

Abstract: The development of a direct, rapid, and sensitive spectroscopic method for the analytical quantification of light (low atomic number) elements represents an important ongoing challenge. For the first time, we review the evolution of laser-induced breakdown spectroscopy (LIBS) technique for trace analysis of light elements in steels. We present studies carried out in both far/vacuum UV and UV–visible spectral regions, and focus on the elements carbon, sulfur, phosphorous, and nitrogen as their presence and content determine key properties of all steel products. In order to facilitate tracking down the evolution of the technique for a particular element/matrix, the review is organized in such a way that a chronological order has always been obeyed. Moreover, important information regarding characterization of a specific element in a given steel sample is tabulated, so that interested readers can easily locate relevant resources. Furthermore, typical examples of recent developments and advances in terms of LIBS instrumentation and systems regarding light elements in steels are summarized. Finally, the article suggests in brief some approaches for further raising the analytical capability and figures of merit of LIBS regarding trace compositional analysis of light elements. In this respect, we suggest combining LIBS with recently developed diode laser-based techniques such as DLIFS and DLAAS. [Copyright &y& Elsevier]

Impression creep tests have been carried out at 923 K on 316LN SS containing 0.07, 0.14, and 0.22 wt.% nitrogen, under different applied stress levels. It was observed that the impression creep depth versus time curves were similar to the creep curves obtained from conventional uniaxial creep tests. The impression creep curves were characterized by a loading strain and primary and secondary creep stages similar to uniaxial creep curves. The tertiary stage observed in uniaxial creep curves was absent. The steady-state impression velocity was found to increase with increasing applied stress. The equivalent steady-state creep rates calculated from impression velocities were found to be in good agreement with the steady-state creep rates obtained from conventional uniaxial creep tests. Equivalence between applied stress and steady-state impression velocity with uniaxial creep stress and steady-state creep rate, respectively, has been established based on the laws of mechanics for time-dependent plasticity. It was found that impression velocity was sensitive to the variation in nitrogen content in the steel; impression velocity decreased with increasing nitrogen content, and the results obtained in this study were in agreement with those obtained from uniaxial creep tests. [ABSTRACT FROM AUTHOR]

Thepurpose of this paper is to study the effect of high nitrogen content on corrosion behavior of austenitic stainless steels in seawater under severe conditions such as tensile stresses and existence of sensitization in the structure. A constant tensile stress has been applied to sensitized specimens types 304, 316L, 304LN, 304NH, and 316NH stainless steels. Microstructure investigation revealed various degrees of stress corrosion cracking. SCC was severe in type 304, moderate in types 316L and 304LN, and very slight in types 304NH and 316NH. The electrochemical polarization curves showed an obvious second current peak for the sensitized alloys which indicated the existence of second phase in the structure and the presence of intergranular stress corrosion cracking. EPR test provided a rapid and efficient nondestructive testing method for showing passivity, degree of sensitization and determining IGSCC for stainless steels in seawater. A significant conclusion was obtained that austenitic stainless steels of high nitrogen content corrode at a much slower rate increase pitting resistance and offer an excellent resistance to stress corrosion cracking in seawater. [ABSTRACT FROM AUTHOR]

The nitrogen belongs to elements which have significant impact in steel mechanical properties. The influences of individual elements on the properties of solution of nitrogen in the metal bath, on the process of nitrogen dissolution in connection with decarburisation process and also influences of some important factors on the possibilities of nitrogen regulation during the refining period were investigated in this work. The path for production of steel with regulated nitrogen content relies on the combination of knowledge of nitrogen thermodynamics, mechanism and kinetics of nitrogen sorption and desorption, together with possibilities of steel melt properties prediction and also with metallurgical actions leading to the control of required chemical composition. [ABSTRACT FROM AUTHOR]

The effects of variations in free nitrogen content on the microstructure and room-temperature tensile properties of laboratory processed dual-phase (DP) sheet steels with a base composition (wt pct) of 0.1C-2.0Mn-0.2Mo-0.2Cr were evaluated. Systematic variations in aluminum and nitrogen content along with coiling temperature were used to create a range of interstitial nitrogen contents and microstructure variations after hot rolling. Two cold rolling reductions of 40 and 70 pct were applied before intercritical annealing. Tensile properties show increasing strength and decreasing total elongation with increasing nitrogen content. Increasing the coiling temperature and adding Al diminished the N effects, while increased cold reduction increased tensile strength in some instances. Microstructural observations indicate an increase in martensite fraction with increased prior cold reduction, while increased coiling temperature decreased the fraction of martensite. [ABSTRACT FROM AUTHOR]

The effect of sampling methods on the detection of N content in the high nitrogen steel (HNS) was studied by variance analysis method. In the experiments, two kinds of samples (rod sample and chip sample) were chosen. It was showed that when the N content was in the range of 0.06%∼0.4%, the results obtained by two methods were almost the same, indicating that both were suitable to identify the N in the steel. However, when the N content was higher than 0.4%, the result obtained using chips as sample was lower than that using rod. The N2 bubble in the rod sample might cause error since it didn't comprise the N content. Hence, the N content could be reflected more accurately by the chip samples. Based on the difference of N content detected by two methods, the shrinkage rate was analyzed theoretically and found to be inversely proportional to the pressure of N2 bubbles in steel. [ABSTRACT FROM AUTHOR]

Austenitic stainless steels are expected to be a major material for boiler tubes and steam turbines in future ultra-supercritical (USC) fossil power plants. It is of great interest to maximize the creep strength of the materials without increasing the cost. Precipitation strengthening was found to be the best and cheapest way for increasing the creep strength of such steels. This study is concerned with improving creep properties of a high nitrogen Nb-stabilized 15Cr-15Ni austenitic alloy through introducing a high number of nanosized particles into the austenitic matrix. The addition of around 4 wt pct Mn and 0.236 wt pct N into the 15Cr-15Ni-0.46Si-0.7Nb-1.25Mo-3Cu-Al-B-C matrix in combination with a special multicycled aging-quenching heat treatment resulted in the fine dispersion of abundant quantities of thermally stable (Nb,Cr,Fe)(C,N) precipitates with sizes of 10 to 20 nm. Apart from the carbonitrides, it was found that a high number of coherent copper precipitates with size 40 to 60 nm exist in the microstructure. Results of creep tests at 973 K and 1023 K (700 °C and 750 °C) showed that the creep properties of the investigated steel are superior compared to that of the commercial NF709 alloy. The improved creep properties are attributed to the improved morphology and thermal stability of the carbonitrides as well as to the presence of the coherent copper precipitates inside the austenitic matrix. [ABSTRACT FROM AUTHOR]

Effects of nitrogen content on the microstructure, hardness, and friction coefficient of Ti-Mo-N coating films were investigated. Ti-Mo-N films were deposited onto an AISI304 stainless steel substrate by reactive r.f. sputtering in the mixture of argon and nitrogen gases with various gas flow rates. The hardness and friction coefficients were measured by nanoindentation and ball-on-disk testing systems, respectively. The hardness of the Ti-Mo-N films increased with increasing a nitrogen gas flow rate $$ \left( {f_{{{\text{N}}_{2} }} } \right) $$ and showed a maximum hardness of about 30 GPa at a $$ f_{{{\text{N}}_{2} }} = 0.3\,{\text{ccm}} $$. On the one hand, the films deposited at $$ f_{{{\text{N}}_{2} }} \ge 1.0\;{\text{ccm}} $$ showed a constant hardness value of approximately 25 GPa. On the other hand, the friction coefficient of the Ti-Mo-N film decreased with increasing N content and was 0.44 in the film deposited at $$ f_{{{\text{N}}_{2} }} = 2.0\;{\text{ccm}}. $$ [ABSTRACT FROM AUTHOR]

Abstract: The focus of the study is to establish the role of nitrogen addition to type 304L stainless steel, in sensitised condition, on the crack growth rate (CGR) by intergranular stress corrosion cracking (IGSCC) in the simulated boiling water reactor (BWR) environment. The CGR studies were carried out for two heats of type 304L stainless steel with 0.10 and 0.16wt.% nitrogen and at different dissolved oxygen (DO) levels in high temperature demineralised water whose chemistry was maintained in a recirculating loop. The degree of sensitisation (DOS) was characterised quantitatively by double loop electrochemical potentiodynamic reactivation (DL-EPR) technique. The results clearly show that the susceptibility to IGSCC was substantially lower in the stainless steel with a higher level of nitrogen as reflected by the CGR values. This was attributed to the beneficial role of nitrogen addition against sensitization i.e. lesser coverage of the chromium depleted regions and higher level of chromium in the depleted regions in the stainless steels with higher nitrogen content. [Copyright &y& Elsevier]

Abstract: Biological soil crusts are important cover in arid desert landscapes, yet their importance as habitats to secondary producers such as ants is relatively unknown. This study was conducted to determine if the presence and development of biological soil crusts on dune surfaces stabilized by revegetation facilitates ant establishment and survival. We measured topsoil properties and crustal features during different successional stages, which were characterized by cyanobacteria and algae, lichens, and mosses, respectively. The species richness and abundance (nest density) of ants were closely associated with silt content, soil organic matter, nitrogen and soil moisture, as well as topsoil temperature. However, ant nest distribution was largely dependent on the biomass and thickness of crusts and topsoil. These findings provide evidence that the recovery or development of biological soil crusts on dune surfaces in the Tengger Desert could favor and maintain higher ant species diversity. Therefore, the disturbance of crusts would result in a reduction of ant species richness and abundance in desert systems. [ABSTRACT FROM AUTHOR]

Stainless steel samples with 100% austenitic microstructure and alloyed with 0.9 wt-% of nitrogen in solid solution were tested under vibratory cavitation experiments in distilled water to study the cavitation-erosion wear (EC) at grain size level (mesoscale). Fully austenitic samples were obtained by high temperature gas nitriding (HTGN) a commercially available dúplex stainless steel, UNS S31803. The samples were characterized by electron backscattering diffraction, EBSD to obtain the crystalline orientation of individual grains. In addition, mass loss measurements were obtained and surface damage evolution was analyzed by scanning electron microscopy (SEM) at different times of the test. These results were analyzed as a function of the prior crystallographic characterization. For comparison, a conventional austenitic stainless steel, UNS S30403, was also investigated. It was observed that both the nucleation and the growth of damage are heterogeneous at the grain-size scale due to mesoscale plasticity an isotropy, induced during the CE tests. The heterogeneous character of the cavitation damage is related to both the grain boundary character and the microtexture inside the grains. [ABSTRACT FROM AUTHOR]

High nitrogen face centred cubic phase formed on the nitrogen modified Fe–Cr–Ni austenitic stainless steel, which is named by γN phase, has a combined wear and corrosion resistance. X-ray diffraction (XRD) patterns of the γN phase on the stainless steel depict a set of broad and asymmetry diffraction peaks with a peak shift to low Bragg angles and a decrease in intensity, even disappearing of some peaks of high index planes, from each austenite peak for the γ matrix. The peak shift of the XRD patterns was first explained by Warren's XRD theory by Blawert et al. (Surf. Coat. Technol., 2001, 136, 181). In this paper, a systematic study of XRD on the peak shift, peak asymmetry, peak broadening and peak intensity of the γN phase has been carried out, based on a fault induced scattering geometry in diffraction to imperfect crystals by Warren's theory and Wagner's method. Both the higher deformation faults density α in a range of 0·02–0·25 and the lower twin faults density β of 0·01–0·1 were successfully used to describe the line profiles in the XRD patterns of the γN phase formed on plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel. A novel stacking faults factor Sαβ dependent on α and β described, in good agreement, the peak intensity of the γN phase. The calculated XRD patterns of the γN phase using the imperfect crystals model of a face centred cubic phase with a higher deformation faults density and a lower twin faults density were associated with the experimentally structural characteristics. [ABSTRACT FROM AUTHOR]

The chemical structure and corrosion behaviour of stainless steel coatings with nitrogen contents up to 40 at.-% have been investigated using X-ray photoelectron spectroscopy and electrochemical tests, respectively. X-ray photoelectron spectroscopy revealed that nitrogen existed in a high binding energy form (N1s≈400 eV) at the very surface of the passive film and a nitride-like state (N1s=397·2 eV) within the coatings. For Cr, an additional peak was observed (at Cr2p=574·7 to 574·8 eV) with a binding energy that fell between those for metallic Cr and Cr nitrides. All of the coatings possessed corrosion resistance superior to that of bulk 316L in 1·0 mol L-1 HCl. The passive corrosion current density initially decreased with increasing nitrogen content up to 8 at.-% above which the current density was below the resolution of the potentiostat (<0·001 mA cm-2). The breakdown potential for the coatings did not change with increasing nitrogen content and was due to transpassive dissolution rather than localised corrosion. Significant substrate corrosion was observed at defects and flaws within the coatings. [ABSTRACT FROM AUTHOR]

Tribological properties of a single high nitrogen face centred cubic phase γN layer formed on the plasma based low energy nitrogen ion implanted AISI 316 austenitic stainless steel were investigated on a ball on disc tribometer against the same stainless steel counterface under a normal load of 2 N with a sliding speed from 0·16 to 0·39 m s-1. The microhardness of the γN phase layer with a thickness of ∼13 μm and a nitrogen peak concentration of ∼35 at-% was measured to be ∼22 GPa. During the sliding for 1 h, the faint wear tracks of the γN phase layer against the same stainless steel ball were observed with all the sliding speeds. The friction coefficient of the γN phase layer changed in the range from 0·85 to 0·70 with increasing sliding speed. Formation of the γN phase layer on the stainless steel significantly improved the wear resistance of the stainless steel against the same stainless steel. An oxidative wear mechanism of the γN phase was found instead of an adhesive wear mechanism of the original stainless steel because the γN phase was prone to tribochemical oxidation on the worn surface due to the nitrogen supersaturation in austenite matrix. [ABSTRACT FROM AUTHOR]

Factors are considered that affect the behavior of nitrogen in steel melting in electric furnaces, extra-furnace treatment and steel continuous casting. The effect of nitrogen content in charge materials, material used during melting and extra-furnace treatment, oxygen purity and other factors on the possibility of achieving a reduced nitrogen content in electric steels is assessed. Specific recommendations are proposed for implementing the possibility of reducing nitrogen content. [ABSTRACT FROM AUTHOR]

Abstract: Numerical simulation of the long-term precipitate evolution in five different austenitic heat-resistant steels–NF709, Super304H, Sanicro25, CF8C-PLUS and HTUPS–has been carried out. MX and M23C6 are predicted to remain as major precipitates during long-term aging in these steels. While the average size of MX is maintained below several ten nanometers during the aging, that of M23C6 exceeds 100 nm after 100,000 h of aging at 700 ∘C. The addition of 3 wt% Cu produces very fine Cu-rich precipitates during aging in Super304H and Sanicro25. It is found that the amount of Z phase starts to increase remarkably between 1000 and 10,000 h of aging at the expense of MX precipitates in the steels containing a high nitrogen content. However, the growth rate of Z phase is relatively slow and its average size reaches at most a few ten nanometers after 100,000 h of aging at 700 ∘C, compared with 9%–12% Cr ferritic heat-resistant steels. The simulated precipitation sequence and precipitate size during aging are in general agreement with experimental observations. [Copyright &y& Elsevier]

Powder injection molded (PIM) 316L stainless steels are widely used in the form of small components with complicated shapes. In order to attain a high sintered density, 316L is generally sintered at high temperatures and the attendant grain growth and austenitic structure limit hardness and strength compared with low-alloy steels. These disadvantages restrict its use in microminiature structural parts that require wear resistance, corrosion resistance, and high strength, such as biopsy tools, cellular phones, and notebook computers. To address this problem, stainless steels can be sintered in dissociated ammonia and cooled rapidly to obtain high levels of dissolved nitrogen without forming chromium nitrides. However, the nitrogen content is limited at the regular sintering temperature of ~1,350°C. To circumvent this limitation, fine 316L powder (D50 = 4.1 µm) was sintered at a low temperature of 1, 120°C for 2 h in dissociated ammonia to achieve a high sintered density of 7.70 g/cm³ (97.2% of the pore-free density) and a nitrogen content of 0.29 w/o. Hardness and tensile strength were 95 HRB and 740 MPa, respectively, and compare with values of 55 HRB and 450 MPa for regular 316L powders (D50 = 12.0 µm) sintered at the standard temperature of 1,350°C. Subsequent hot isostatic pressing (HIPing) in nitrogen resulted in a nitrogen content of 0.79 w/o and hardness and tensile strength levels of 100 HRB and 800 MPa. [ABSTRACT FROM AUTHOR]

Given the high rate of injection of steel with oxygen in modern high-power arc steelmaking furnaces (close to the rate attained in basic oxygen furnaces), the purity of the oxygen becomes the deciding factor in determining the nitrogen content of the steel. An analysis is made of the factors that affect nitrogen content in the production of steel in modern electric-arc furnaces at Ural Steel. In particular, a determination is made of the extent to which the purity of the oxygen that is used affects the steel’s nitrogen content. [ABSTRACT FROM AUTHOR]

Abstract: With a focus on microstructural hierarchy, work hardening behaviour in high nitrogen-bearing austenitic steel (HNS) was investigated mainly by a combined technique of in situ neutron diffraction and in situ electron backscattering diffraction (EBSD). Stress partitioning due to difference in deformability among grains is enhanced in HNS. The larger stress partitioning among [h k l]-oriented family grains seems to realize high work hardening at a small strain. At a larger strain, dislocation density is higher in HNS than in low nitrogen austenitic steel (LNS), which is a possible reason for high work hardening after straining proceeds, resulting in large uniform elongation. [Copyright &y& Elsevier]

Abstract: Nitrogen content in austenitic manganese steels is usually not reported nor standardized. The present work has found that it typically ranges between 130 ppm and 200 ppm in solution. Microstructural evolution has been studied by optical microscopy, using mainly differential interference contrast mode. Work hardening was analyzed under compression conditions using Hollomon''s fitting and Vickers microindentation hardness measurements at different deformation levels. Even low contents of nitrogen in solution exhibit a significant effect on the slope of stress–strain curves, with strain-hardening exponent values of 0.7, 0.57 and 0.41 for 720 ppm, 130 ppm and 71 ppm of nitrogen, respectively. It was also found that the nitrogen content influences the microstructure of deformed coarse grained polycrystalline austenite, leading to twining and shear bands at the upper level of nitrogen, while it was not clearly found in the samples with lower nitrogen content. [Copyright &y& Elsevier]

Role of boron in low carbon aluminum-killed cold rolled batch annealed steels has been critically examined. It was found that it is not the absolute boron but B/N ratio that controls the forming properties. Pancake shaped grains (high grain shape anisotropy) are highly desirable for improving the desirable {111} texture, normal anisotropy, and draw ability of the steel sheets. Microstructural analysis showed that the extent of pancaking decreases with increase in B/N atomic ratio and reaches ultimately to formation of equiaxed grains. Low B/N ratio (upto 0.3) resulted in improved mean plastic anisotropy ratio ( rm) value and high grain shape anisotropy, which has been characterized through grain aspect ratio. The desirable orientation in steel with low B/N ratio is attributed to sufficient availability of Al and N to precipitate during batch annealing. Optimum amount of boron, aluminum, and nitrogen in steel has resulted in coarse pancake structure, which is ideally suited for improved formability. [ABSTRACT FROM AUTHOR]

The article presents a study on the association between deformation structure and work hardening behaviour of high nitrogen austenitic steel (HNS.) Two types of HNS that contain about one mass-% of nitrogen with and without manganese alloys were tested through application of tensile stress. Findings revealed that variation in work hardening behaviour among the manganese alloys was caused by dislocation substructure changes to the dislocation cell from planar dislocation array.

The article presents a study on the stacking fault energy (SFE) of high nitrogen (N) bearing steels. It states that high nitrogen steels (HNS) contain a balance of ductility and strength. It presents nitrogen bearing steels high work-hardening rate wherein it examines the dislocation configuration of various stainless steels through the weak beam method. It also notes on the possible reasons for dislocation planarization such as low supercritical fluid extraction and high nitrogen contents.

Abstract: An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using the high-speed motion analyzer. The tubes in the experiment are 0.014 and 0.018m in inner diameter separately and both 1.0m long. The range of the inclination angles is 0–45° from the vertical. The statistical method is employed to analyze the experimental data. The experiment focused on the effect of the inclination angles on the velocities and the length distributions of the nitrogen Taylor bubbles at different positions along the tubes. The trend of velocity along the tubes is related with θ. At the same position of the tubes, the velocity of the Taylor bubbles increases first, and then decreases with the increase of θ. And the mean Taylor bubble length increases with the increasing x/D along the tubes at various θ. At the same position of the tubes, the mean Taylor bubble length increases first, and then decreases with increasing θ, maximum at 30°. In vertical tubes, standard deviations of the nitrogen Taylor bubble lengths increase with the increasing x/D. For inclined tubes, standard deviations of the nitrogen Taylor bubble lengths increase first, and then decrease with the increasing x/D. [Copyright &y& Elsevier]

Abstract: A high nitrogen austenitic stainless steel (0.9wt% N) and an ordinary 304 austenitic stainless steel were submitted to cavitation-erosion tests in a vibratory apparatus operating at a frequency of 20kHz. The high nitrogen stainless steel was obtained by high temperature gas nitriding a 1-mm thick strip of an UNS 31803 duplex stainless steel. The 304 austenitic stainless steel was used for comparison purposes. The specimens were characterized by scanning electron microscopy and Electron Back Scatter Diffraction. The surface of the cavitation damaged specimens was analyzed trying to find out the regions where cavitation damage occurred preferentially. The distribution of sites where cavitation inception occurred was extremely heterogeneous, concentrating basically at (i) slip lines inside some grains and (ii) Σ-3 coincidence site lattice (CSL) boundaries (twin boundaries). Furthermore, it was observed that the CE damage spread faster inside those grains which were more susceptible to damage incubation. The damage heterogeneity was addressed to plasticity anisotropy. Grains in which the crystallographic orientation leads to high resolved shear stress show intense damage at slip lines. Grain boundaries between grains with large differences in resolved shear stress where also intensely damaged. The relationship between crystallite orientation distributions, plasticity anisotropy and CE damage mechanisms are discussed. [Copyright &y& Elsevier]

The effect of aluminum and nitrogen on the microstructure of the ultra-low-carbon Nb-IF (interstitial free) steel was investigated. Steel with higher aluminum and nitrogen contents showed equiaxed ferrite grains in the hot-rolled steel and continuously annealed steel. Decrease in either aluminum or nitrogen content, however, resulted in the mixed microstructure of small and large grains with wavy grain boundaries in the hot-rolled steel and the pancake-shaped ferrite grains in the continuously annealed steel. [ABSTRACT FROM AUTHOR]

The characteristics and classification of decarburization and denitrogenation in the vacuum vessel for stainless steel production are analyzed. Based on the analysis of movements of the liquid steel and bubbles, the kinetics of decarburization and denitrogenation in the vacuum oxygen decarburization (VOD) process has been studied. A kinetic model of decarburization and denitrogenation has been developed to simulate the VOD process, considering each reaction zone as oxygen blowing crater, bottom blowing plume, steel/slag interface, and plume eye. As a result, it is possible to quantify the contribution of each reaction zone in decarburization and denitrogenation rate at a different stage in the VOD process. Specific trials at a vacuum induction furnace were performed to refine stainless steel in vacuum carbon deoxidation (VCD) and VOD style, respectively. The trial results are in good agreement with the model calculation. Combining the trials and the model calculation and the influence of temperature control, critical carbon content selection on the terminal total [C] + [N] content can be discussed further to provide a reasonable proposal for high-quality ferritic stainless steel production. [ABSTRACT FROM AUTHOR]

Abstract: In this study, phase transformation of α to γ in a nanostructured high-nitrogen Fe–18Cr–11Mn austenitic stainless steel powder produced by mechanical alloying (MA) was investigated. MA was performed under nitrogen and argon atmospheres using a high-energy planetary ball mill. The obtained results from X-ray diffraction (XRD) and Oxygen/Nitrogen analyser revealed that nitrogen solubility in powders significantly increases by increasing the milling time under nitrogen atmosphere. Nitrogen solubility reaches to 0.65wt% in samples milled for up to 100h. The obtained results also indicated that MA in argon (Ar) atmosphere produces a ferrite structure after 120h of milling. In contrast, a completely austenitic structure was obtained by performing MA for 100h in nitrogen (N2) atmosphere. Nanostructured powders of below 10nm grain sizes were obtained by MA under both Ar and N2 atmospheres. [Copyright &y& Elsevier]

Since Ellman’s seminal works, over the past ten years tert-butanesulfinimines have proved to be useful chiral amino intermediates for organic synthesis. Through highly stereoselective reactions, amongst which reductions, nucleophilic 1,2-additions and ylide condensations, a broad range of nitrogen-containing compounds has been synthesized. Although the stereoselectivity levels are high in most cases, the sense of the stereoinduction is generally not predictable. The object of this critical reviewis to present the models proposed to rationalize the stereochemical outcome of the reactions involving tert-butanesulfinimines and to point out an obvious lack of homogeneity amongst them (128 references). [ABSTRACT FROM AUTHOR]

In its oxygen converter production facility, the Benxi Iron and Steel Co., Ltd. has developed production of IF automotive sheet steel (with maximum carbon content 0.0025% and maximum nitrogen content 0.0030%) on the BOF (150 metric tons) → LF → RH → CC line. This product is intended for production of both interior and exterior parts of Chinese automobiles. Production of these steels on the BOF (150 metric tons)→ LF → RH → FTSC line still has not been fully mastered, since the issue of surface quality for hot-rolled sheet has not yet been resolved. [ABSTRACT FROM AUTHOR]

Abstract: The effects of oxygen, H2SO4 concentration and surface roughness on the electrochemical behaviour of high nitrogen bearing stainless steel (HNS) in acidified 0.5M NaCl solution were investigated using potentiodynamic polarization method. The results revealed three corrosion potentials indicating an unstable system. The number of the potentials was influenced by H2SO4 concentration. Three potentials existed above 0.011M H2SO4, two between 0.011 and 0.0065M H2SO4 and one below 0.0065M H2SO4. Oxygen increased the number of corrosion potential at 0.005M H2SO4 +0.5M NaCl solution while surface roughness had no noticeable influence on the number of potentials but increased the values of the corrosion potentials and passivation current densities with increase in the surface roughness. The corrosion mechanism has been discussed using the ideal polarization curve models. [Copyright &y& Elsevier]

Microwave carbothermal nitridation was used to prepare vanadium nitride from vanadium pentoxide and carbon black, under flowing nitrogen gas at atmospheric pressure. The effect of synthesis temperature, soaking time and the initial concentration of carbon on the final nitrogen content was studied. The nitrogen content in the products reached 12 to 16 wt-%, well within the current requirements of the steelmaking industry. [ABSTRACT FROM AUTHOR]

In welding of high nitrogen steel (HNS), it is essential to control the nitrogen content and porosity in the weld metal. In this paper, the influence of shielding gas composition and heat input on the nitrogen content and porosity in the weld metal of HNS was investigated by gas tungsten arc welding. The experimental results indicate that the weld nitrogen content increases as N2 in the shielding gas is increased in the same heat input of welding. The weld nitrogen content decreases with increasing the heat input for pure argon used as a shielding gas, whereas it increases with increasing the heat input for the shielding gas including some nitrogen. The nitrogen pore can be avoided when the nitrogen content in the shielding gas is <4% in the heat input range of 528–2340 J mm–1. [ABSTRACT FROM AUTHOR]

Abstract  Fungal infection of the filamentous cyanobacterium Anabaena smithii was observed in Lake Shumarinai in 2004–2006. Two fungal species were found to parasitize the specialized cells of A. smithii. These fungi might not correspond to the chytrid species that the previous studies reported as the parasites for Anabaena species. One fungus showed selective attachment to the akinete (akinete type). The filaments parasitized by this fungus increased in August 2004 and October 2006, when akinete and filament densities also increased. The maximum percentage of parasitized filaments was 3.2% of all filaments in October 2006. The other fungus was usually attached to the heterocyst (heterocyst type). The filaments parasitized by this fungus increased in October from 2004 to 2006. The maximum percentage of parasitized filaments was 20.6% in October 2004. The biomass of A. smithii was not suppressed by akinete-type fungus because of the low percentage of parasitized filaments. The heterocyst-type fungus might disturb the nitrogen fixation, but its effect was negligible due to a high concentration of available nitrogen for planktonic algae in Lake Shumarinai. [ABSTRACT FROM AUTHOR]

Abstract: Optical emission spectroscopy of atomic lines and molecular vibrational bands in N2, H2/N2 and Ar/N2 plasmas at steel nitriding conditions have been reported as an application of this diagnostic to plasma nitriding. An increase in Ar I intensity as Ar percentage increases in an Ar/N2 mixture is observed, while the effect on N2 + emission has a decrease, just the reverse of Ar I emission profile. As electron energy distribution function, EEDF, shifted to high electron energy as Ar percentage increases in the mixture, the presence of high-energy electron at high gas temperature of discharge can be predicted. It has also been found that pressure effect on N2 + band in pure nitrogen plasma is to increase the band intensities. Spatial distribution of N2 +(0,1) and N2 +(0,2) emission profile in N2/H2 mixture reveals shrinking of negative glow by 10 mm in the presence of 10% H2 and 90% N2 relative to a pure N2 plasma. [Copyright &y& Elsevier]

Abstract: A typical heteroatom (nitrogen)-doped carbon materials were successfully synthesized through the carbonization of a hybrid containing traditional carbon black covered by in situ polymerized polyaniline. The nitrogen content onto carbon can be adjusted up to 5.1at.% by changing the coverage of polyaniline. The effects of nitrogen doping on the surface physical and electrochemical properties of carbon were studied using XPS, XRD and HRTEM, as well as CV and EIS techniques. With increasing nitrogen doping, the carbon structure became more compact, showing curvatures and dislocations in the graphene stacking. The nitrogen-doped carbon also exhibited a higher accessible surface area in electrochemical reactions, and a lower charge transfer resistance at the carbon/electrolyte interface. Moreover, to investigate the influence of nitrogen doping on the electrocatalytic activity of the PtRu/C catalyst, comparisons in CO stripping and methanol oxidation were carried out on PtRu catalysts supported by non-doped and nitrogen-doped carbon. Since the promotional roles of nitrogen doping, including the high electrochemically accessible surface area, the richness of the disordered nanostructures and defects, and the high electron density on N-doped carbon supports, contribute to the synthesis of well-dispersed PtRu particles with high Pt utilization and stronger metal-support interactions, an enhanced catalytic activity for methanol oxidation was obtained in the case of the PtRu/N-C catalyst in comparison with the traditional PtRu/C catalyst. [Copyright &y& Elsevier]

The structure and mechanical properties of nitrogen-bearing (up to 0.45% N) austenitic steel of type 04Kh20N6G11AM2BF are studied after hot rolling, hardening from different temperatures, and cold deformation. [ABSTRACT FROM AUTHOR]