Steel Particles Research Articles

Investigation of the structural, electronic and mechanical properties of Ca-SiO2 compound particles in steel based on density functional theory

Investigation of the structural, electronic and mechanical properties of Ca-SiO2 compound particles in steel based on density functional theory

Grain refinement of A517 steel by inoculation with Al–5Ti–B master alloy

The edge-to-edge matching model was used to identify TiB2 as a potential grain refiner to refine the high temperature δ-ferrite in low carbon steels. To effectively introduce the grain refiner, Al–5Ti–B master alloy (MA) was used to add TiB2 particles into an A517 steel. However, there was no grain refinement in the as-cast A517 steel, attributed to the decomposition of TiB2 particles in the molten A517 steel, into Ti and B. As a result, BN particles formed on the pre-existing Al2O3 particles were detected within prior austenite grains. Nevertheless, there was significant grain refinement after reheating the A517 ingots to 1150 °C, isothermally holding for 2 h and air cooling. The austenite grain size of the reheated A517 steel was decreased from 318 ± 70 μm to 38 ± 4 μm using 0.1 wt% Al–5Ti–B MA. Grain refinement was caused by Ti-containing nanometre-sized precipitates along prior austenite grain boundaries inhibiting the grain growth. The grain refinement improved the strength and ductility of ingots after reheating and improved workability for the production of hot worked products.

Study on the failure analysis of four metals for anaerobic fermentation reactor based on numerical simulation and electrochemical method

The core problem of low energy consumption anaerobic fermentation reactor is that the reactor can make reasonable and effective use of energy from two aspects of quantity and quality, so as to ensure the anaerobic fermentation performance of the reactor and make it run efficiently and energy-saving. However, serious corrosion of metal for reactors was found during operation, and the selection of reactor materials became the key to restrict biogas production. In this paper, the corrosion characteristics of the four metals including Q235A steel, Q345A steel, 45# steel and 3Cr13 steel were determined by corrosion morphology, mechanical and electrochemical experiments. The results showed that the corrosion product particles of Q235A steel were polygonal, showing a good cross-linking feature, which was better than that of Q345A and 45# steels. However, there was no obvious boundary between corrosion product particles of 3Cr13 steel. The presence of Fe3C in the corrosion products of 3Cr13 steel and the observation of micro-cracks on the surface at nanometer scale indicated that the intergranular corrosion of 3Cr13 steel was dominated. For another aspect, with the increase of CO2 and CH4 content, the corrosion rate of the four metals was generally accelerated, in which the Q235A steel showed the best performance under different conditions. In addition, Q345A and 45# steels showed relatively good corrosion resistance, under which the total mole of mixed gas (CO2/H2O/CH4) was lowest.

Effect of electropulsing treatment on the precipitation behavior of MnS in sulfur-containing microalloyed 49MnVS3 steel

An experimental investigation has been conducted with respect to the influence of electropulsing treatment (EPT) on the 2D and 3D morphologies, distribution, number and size of MnS precipitates in the high-sulfur micro-alloyed 49MnVS3 steel. After the application of electric current pulse with a peak pulsed voltage of 30 V, the microstructure was refined due to the increasing nucleation rate of particles in liquid steel. Moreover, compared with the untreated steel with spherical MnS randomly distributed in the matrix, the MnS precipitates moved directionally to aggregate on the bottom and top surfaces of the ingot in order to minimize the free energy of the system in case of EPT. For untreated steel samples, the number of MnS was 409 (bottom), 579 (middle) and 437 (top), while that of the treated samples were 226 (bottom), 38 (middle) and 224 (top) in the scanning area of 2.65 × 107 µm2 with ASPEX. The number of MnS with small size decreased while the large-size MnS increased with the application of EPT.

An Asymmetric Micro-Three-Coil Sensor Enabling Non-Ferrous Metals Distinguishment

At present, when performing material identification of metal wear debris, most sensors can only roughly distinguish between ferromagnetic and non- ferromagnetic metal wear debris, but fail to distinguish them deeply. To achieve fine detection of metal wear debris in the oil, this paper designs an asymmetric micro-three-coil sensor, which generates an asymmetric magnetic field by using two excitation coils of different sizes. Different metal wear debris are affected differently in the magnetic field and the shape of the output signal is also different, therefore, the wear debris material can be distinguished by the shape of the signal of the induction electric potential output from the induction coil alone, and the wear debris size can be determined by the amplitude of the signal. Copper particles, aluminum particles, iron particles and 304 stainless steel particles were selected as experimental objects, and the experimental results showed that the material differentiation of these four types of particles can be achieved by the asymmetric magnetic field of the sensor. The method provides a new research direction for the inductive method to distinguish non-ferrous metals, which is important for the fine detection of multi-parameter pollutants and the diagnosis and monitoring of mechanical system faults.

Effect of radio-frequency plasma spheroidization on the microstructure and mechanical properties of 10Cr ferritic oxide dispersion-strengthened steel

Reducing the porosity of irregularly shaped mechanically alloyed oxide dispersion-strengthened (ODS) steel powders is critical for their application at cryogenic temperatures. Although the plasma rotating electrode process has been widely used as a suitable method for producing spherical powders, its high cost and low powder yield impede its application. Thus, we investigated the feasibility of applying plasma spheroidization on ODS steel particles, to reduce their porosity, by investigating the influence of radio-frequency plasma spheroidization on the microstructure and mechanical properties of 10-Cr ODS steel. The ODS steel powder was ball-milled and then spheroidized prior to consolidation. The prepared samples were analyzed using X-ray diffraction, electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) as well as subjected to tensile and impact tests. The EBSD analysis revealed that the grains in the plasma-spheroidized sample were coarser than those in the non-spheroidized sample, and thus, the room- and cryogenic-temperature Charpy impact strengths of the latter were superior to those of the former sample. TEM analysis showed that the average particle size of plasma-spheroidized ODS steel was slightly higher than that of the non-plasma-spheroidized ODS steel. Furthermore, the room-temperature yield strength of the non-spheroidized ODS was higher than that of the spheroidized ODS because of the finer grains of the former. In the future, plasma spheroidization can be combined with other techniques to obtain completely dense ODS steel with increased upper shelf energies for various advanced and military applications.

Tritiated Steel Micro-Particles: Computational Dosimetry and Prediction of Radiation-Induced DNA Damage for In Vitro Cell Culture Exposures.

Biological effects of radioactive particles can be experimentally investigated in vitro as a function of particle concentration, specific activity and exposure time. However, a careful dosimetric analysis is needed to elucidate the role of radiation emitted by radioactive products in inducing cyto- and geno-toxicity: the quantification of radiation dose is essential to eventually inform dose-risk correlations. This is even more fundamental when radioactive particles are short-range emitters and when they have a chemical speciation that might further concur to the heterogeneity of energy deposition at the cellular and sub-cellular level. To this aim, we need to use computational models. In this work, we made use of a Monte Carlo radiation transport code to perform a computational dosimetric reconstruction for in vitro exposure of cells to tritiated steel particles of micrometric size. Particles of this kind have been identified as worth of attention in nuclear power industry and research: tritium easily permeates in steel elements of nuclear reactor machinery, and mechanical operations on these elements (e.g., sawing) during decommissioning of old facilities can result in particle dispersion, leading to human exposure via inhalation. Considering the software replica of a representative in vitro setup to study the effect of such particles, we therefore modelled the radiation field due to the presence of particles in proximity of cells. We developed a computational approach to reconstruct the dose range to individual cell nuclei in contact with a particle, as well as the fraction of "hit" cells and the average dose for the whole cell population, as a function of particle concentration in the culture medium. The dosimetric analysis also provided the basis to make predictions on tritium-induced DNA damage: we estimated the dose-dependent expected yield of DNA double strand breaks due to tritiated steel particle radiation, as an indicator of their expected biological effectiveness.

On improvement of the interlaminar shear strength of carbon fiber/epoxy laminates with magnetically guided steel particles

To enhance the interlaminar shear strength of carbon fiber/epoxy resin laminate, stainless steel particles were filled between laminas and uniformly arranged along the thickness direction by the outside magnetic field during manufacturing the composites. Specimens with five particle densities of 15 g/m2, 30 g/m2, 45 g/m2, 60 g/m2, and 75 g/m2 were prepared for testing. The interlaminar shear strength was obtained by short beam shear test and compared with the one of specimens without particles and with the randomly distributed particles between layers. Both modified equivalent stiffness predicting model and bridging model were established. A segmented prediction model was proposed by combining the two models. The error between results obtained by the proposed model and test was less than 10%. Results showed that the interlaminar shear strength of all specimens filled with particles was improved except for the one with particle density of 15 g/m2. The interlaminar shear strength of the specimens with randomly distributed particles between layers increased by 6.12%, 7.29%, 7.43%, and 6.01% for specimens with particle densities of 30 g/m2, 45 g/m2, 60 g/m2, and 75 g/m2. The interlaminar shear strength of the specimens with magnetically guided particles aligned along the thickness direction increased by 9.78%, 14.39%, 17.93%, and 20.39% for the four particle densities. This indicated that the interlaminar shear strength of the carbon fiber/epoxy laminate could be effectively enhanced by aligning the particles between laminas along the thickness direction using the outside magnetic field guidance during manufacturing the composites.

Biokinetics and Internal Dosimetry of Tritiated Steel Particles.

Decommissioning fission and fusion facilities can result in the production of airborne particles containing tritium that could inadvertently be inhaled by workers directly involved in the operations, and potentially others, resulting in internal exposures to tritium. Of particular interest in this context, given the potentially large masses of material involved, is tritiated steel. The International Commission on Radiological Protection (ICRP) has recommended committed effective dose coefficients for inhalation of some tritiated materials, but not specifically for tritiated steel. The lack of a dose coefficient for tritiated steel is a concern given the potential importance of the material. To address this knowledge gap, a “dissolution” study, in vivo biokinetic study in a rodent model (1 MBq intratracheal instillation, 3-month follow-up) and associated state-of-the-art modelling were undertaken to derive dose coefficients for model tritiated steel particles. A committed effective dose coefficient for the inhalation of 3.3 × 10−12 Sv Bq−1 was evaluated for the particles, reflecting an activity median aerodynamic diameter (AMAD) of 13.3 µm, with the value for a reference AMAD for workers (5 µm) of 5.6 × 10−12 Sv Bq−1 that may be applied to occupational inhalation exposure to tritiated steel particles.

4D imaging of void nucleation, growth, and coalescence from large and small inclusions in steel under tensile deformation

• High spatial and temporal resolution synchrotron X-ray CT enabled 4D imaging of void nucleation, growth, and coalescence with unprecedented details. • Large inclusion particles in SA508 steel led to large and prolate voids which, while striking, did not affect crack formation. • The final fracture was induced by densely populated carbide precipitates that led to small but closely spaced voids which quickly coalesced to form micro-cracks. • The results challenge established theories on ductile fracture and could potentially lead to new strategies for steel making. Samples of SA508 grade 3 nuclear pressure vessel ferritic steel were subjected to tensile straining whilst being simultaneously imaged in 3D in real time using high resolution, high frame rate time-lapse synchrotron computed tomography (CT). This enabled direct observation of void development from nucleation, through growth to coalescence and final failure validating many inferences made post-mortem or by theoretical models, as well as raising new points. The sparse, large inclusions were found to nucleate voids at essentially zero plastic strain (consistent with zero interfacial strength); these became increasingly elongated with straining. In contrast, a high density of small spherical voids were found to nucleate from the sub-micron cementite particles at larger strains (> 200%) only in the centre of the necked (high triaxiality) region. An interfacial strength approaching 2100 MPa was inferred and soon after their nucleation, these small voids coalesce to form internal microcracks that lead to the final failure of the specimen. Perhaps surprisingly, under these conditions of generally low triaxial constraint the large voids are simply cut across and appear to play no significant role in determining the final failure. The implications of these results are discussed in terms of ductile fracture behaviour and the Gurson model for ductile fracture.

Development of AA6061/316 stainless steel surface composites via friction stir processing: Effect of tool rotational speed

Metallic and alloy particles are recognized as alternatives to ceramic reinforcements to improve the overall characteristics of Al metal matrix composites. The present study aimed to investigate the friction stir processing/manufacturing of the 316 stainless steel particles reinforced AA6061 Al matrix composites by varying the tool rotational speeds. The microstructure, tensile, hardness, wear, corrosion behavior, and shear punching tests of the composites were studied. The results showed that the friction stir processing route produced no particle-matrix reaction in the composite and dislocation entanglements were formed close to the inherent 316 stainless steel particles within the Al matrix. The improved mechanical action of the tool aided particle fragmentation as the average 316 stainless steel particle sizes decreased from 41.88 to 26.89 μm. As a result of the dynamic recrystallization and particle-assisted pinning effects, the mean grain sizes of the composite decreased from 7.48 to 4.31 μm when the tool rotational speed was raised. An increment in the tool rotational speed (800–1200 rpm) triggered a rise in the maximum shear force (1198–1562 N), tensile strength (200.09–279.98 MPa), and maximum hardness value (121–139 HV) of the composite while a favorable decrease in the composite's wear rate (0.63–0.20 mg/m) and the friction coefficient (0.38 ± 0.01–0.21 ± 0.01) ensued. The composite's improvement is attributable to the homogeneous spread of dislocation.

Early Spalling Analysis of Large Particles in High-Cr Steel during Thermal Fatigue: Relevant Mechanisms.

The aim of this study was to investigate the surface deterioration of high-Cr roll steel caused by the spalling of larger particles during thermal fatigue. The mechanisms of surface deterioration due to spalling of larger particles are discussed. Using a laboratory thermal fatigue test that replicates hot rolling conditions, samples were tested cyclically (up to 4500 times) at maximum cycle temperatures of 500, 600 and 700 °C, followed by water cooling. Specimens with surface deterioration were selected for analysis, revealing important influencing parameters, i.e., the combination of test temperatures, chemical composition, thermal stress and microstructural properties, leading to oxidation-assisted crack growth in different directions and consequent surface deterioration due to early spalling of larger particles. Here, we describe the mechanisms of crack propagation, especially in the lateral direction, and their relation to the subsequent spalling of larger particles, which depend on the influence of the local chemical composition on the microstructural constituents, as well as their distribution and properties. The results obtained in this study can be used in the development of roll steel microstructures with improved resistance to the identified mechanisms of surface degradation.

Effect of fine particle shot peening on surface friction of stainless steel and ceramic bracket slots

This study aims to compare the static friction of untreated and fine particle shot peening (FPSP) treated stainless steel and ceramic bracket slots. A total of 60 pieces of stainless steel and 60 pieces of ceramic brackets (Roth prescription, 0.022×0.028 in2) were divided into 3 groups: control (n=20), silica glass bead particle surface treatment (n=20) and stainless steel (SUS316L) particle surface treatment (n=20). Ten brackets of each group were combined with 0.019×0.025 in2 orthodontic stainless steel arch wires and were analyzed for static friction. The remaining 10 brackets of each group were tested for slot surface roughness and hardness. The result shows that stainless steel brackets treated with FPSP exhibited lower static friction, with smoother and harder surfaces than the control group (p<0.05). In contrast, treated ceramic brackets showed no difference from the control group in terms of static friction, roughness, and hardness (p>0.05).

Comparison of Experimental Results from Operating a Novel Fluidized Bed Classifier with CFD Simulations Applying Different Drag Models and Model Validation

A cold-flow lab-scale cross-flow fluidized bed classifier was simulated using the CFD software Barracuda VR®. The purpose of the study was to identify the most suitable drag model and make the model adjustments that provide the best representation of the flow situation in the classifier when comparing the results with the experimental data. Two particle types were used in the simulations and in the experiments: zirconia (median diameter 69 µm, skeletal density 3830 kg/m3) and steel (290 µm, 7790 kg/m3). Ten different cases, with different solids loading values, were investigated: three with pure zirconia particles, three with pure steel particles, and four with a mixture of zirconia (28%) and steel (72%). Several different drag models were tried out in the simulations. However, none of the available models were able to predict the classification efficiency observed in experiments with their default settings. Although most of the drag models correctly predicted the inversely proportional behavior of the classification efficiency vs. solids loading, the classification efficiency was overpredicted. It was observed that a combined WenYu/Ergun drag model gave a wide range of accuracy, by being able to capture the behavior of both dense and dilute particle systems. Even though the predictions of the classification efficiency for steel particles were acceptable, a larger deviation was observed with Geldart A zirconia particles. CFD simulations with the WenYu and Ergun combined drag model were used for further validation against the experimental observations. In this case, previously published experimental data for fluidization of pure Zirconia particles were used. The fluidization of zirconia was modelled in Barracuda VR® with adjustment of the combined WenYu/Ergun drag model parameter (k1), to obtain a suitable validation. Furthermore, the effect of adding the blended acceleration model (BAM) for the fluidization simulations is discussed. It was observed that the fixed bed pressure drop was very accurate compared to the experimental observation, but the pressure drop after the fluidization was slightly overpredicted.

Cold-Sprayed Multilayer Thermal Barrier–Catalytic Coatings for Engine Pistons: Coatings Design and Properties

Yttrium-stabilized zirconia thermal barrier coatings (TBCs) of combustion chambers and piston crowns are used most frequently to increase the chamber temperature and the internal combustion engine efficiency. The development of multilayer metal matrix composite coating is of great importance to diminish the ceramic thermal barrier coating’s brittleness and susceptibility to degradation providing the similar thermal insulation. Our group is developing multilayer TBCs based on intermetallic (Fe-Al) compounds combined with alternating zirconia-based layers made by low-pressure cold spraying (LPCS) and sintering. The Fe-Al intermetallic phase was synthesized during reaction sintering of stainless steel and Al particles in the powder layer previously obtained by cold spraying. A double-nozzle low-pressure cold-spraying gun was used to deposit two layers (stainless steel and Al-YSZ) per one track. The effect of the breaking of the brittle ZrO2 particles due to impingement with the substrate results in the formation of a relatively homogeneous structure with ZrO2 particle size of 3–10 μm. Cold-spray deposition of additional Cu-Ni-Graphene catalytic layers on the TBCs is developed to improve performance and emissions of engines. The microstructure, thermal conductivity, thermal shock behavior and microhardness of TBCs were examined and discussed.

Cyto-Genotoxicity of Tritiated Stainless Steel and Cement Particles in Human Lung Cell Models.

During the decommissioning of nuclear facilities, the tritiated materials must be removed. These operations generate tritiated steel and cement particles that could be accidentally inhaled by workers. Thus, the consequences of human exposure by inhalation to these particles in terms of radiotoxicology were investigated. Their cyto-genotoxicity was studied using two human lung models: the BEAS-2B cell line and the 3D MucilAirTM model. Exposures of the BEAS-2B cell line to particles (2 and 24 h) did not induce significant cytotoxicity. Nevertheless, DNA damage occurred upon exposure to tritiated and non-tritiated particles, as observed by alkaline comet assay. Tritiated particles only induced cytostasis; however, both induced a significant increase in centromere negative micronuclei. Particles were also assessed for their effects on epithelial integrity and metabolic activity using the MucilAirTM model in a 14-day kinetic mode. No effect was noted. Tritium transfer through the epithelium was observed without intracellular accumulation. Overall, tritiated and non-tritiated stainless steel and cement particles were associated with moderate toxicity. However, these particles induce DNA lesions and chromosome breakage to which tritium seems to contribute. These data should help in a better management of the risk related to the inhalation of these types of particles.

A novel rock bolting system exploiting steel particles

The effectiveness of rock bolting in ground control has been extensively investigated, mainly for resin based systems. Alternative coupling materials are needed to have good mechanical performance and to reduce the economic impact. This study proposed a new bolting system exploiting steel particles as coupling material. The applicability of this system was assessed by laboratory and field pullout tests, assisted by digital imaging correlation (DIC), infrared thermography (IRT) and acoustic emission (AE). The results indicated that, for a 20 mm diameter bolt, the suitable steel particle size and corresponding inner diameter of borehole were 1.4 and 28 mm, respectively. For bolts installed in steel tubes, the particles improved the loading capacity compared to the resin bonded ones. Additional pullout tests on cement blocks indicated that steel particles can be effective for hard rock, whilst resin was a better choice for bolting of soft rock. Similar understanding was obtained by pullout tests in engineering fields, which demonstrated that the steel particles coupled bolts can provide favorable effects in hard rock mass, while the effects were negligible when installed in extremely soft coal mass. The wide set of multi-technique measurements helped to understand the mechanisms involved in the performance of the bolting system with coupling steel particles.

Bioaccumulation, release and genotoxicity of stainless steel particles in marine bivalve molluscs.

During the decommissioning and removal of radioactive material in nuclear facilities, fine, tritiated dusts of stainless steel, cement or tungsten are generated that could be accidently released to the environment. However, the potential radio- and ecotoxicological effects these tritiated particles may have are unknown. In this study, stainless steel particles (SSPs) representative of those likely to be tritiated are manufactured by hydrogenation and their tissue-specific bioaccumulation, release (depuration) and subsequent genotoxic response have been studied in the marine mussel, Mytilus galloprovincialis, as a baseline for future assessments of the potential effects of tritiated SSPs. Exposure to 1000μgL-1 of SSPs and adopting Cr as a proxy for stainless steel revealed relatively rapid accumulation (∼5h) in the various mussel tissues but mostly in the digestive gland. Over longer periods up to 18 days, SSPs were readily rejected and egested as faecal material. DNA strand breaks, as a measure of genotoxicity, were determined at each time point in mussel haemocytes using single cell gel electrophoresis, or the comet assay. Lack of chemical genotoxicity was attributed to the rapid processing of SSP particles and limited dissolution of elemental components of steel. Further work employing tritiated SSPs will enable radio-toxicology to be studied without the confounding effects of chemical toxicity.

Effect of Interlaminar Toughness on the Residual Compressive Capacity of Carbon Fiber Laminates with Different Types of Delamination

In this paper, the effect of interlaminar properties and the type of delamination defects on the residual compression properties of carbon fiber laminates were experimentally investigated. A new method, which employed magnetic force to guide the arrangement direction of stainless steel particles between layers of laminates, was adopted to improve the interlayer toughness. The digital image correlation, C-scan, and micro-CT were used to measure and identify the compression failure damages. Test results showed that the compressive strength of the intact carbon fiber laminates was 299.37 MPa, and the one of specimens containing the deeply buried delamination, the through-width delamination, and the surface delamination decreased by 55.98 MPa, 58.69 MPa, and 60.23 MPa, respectively. The compressive strength of the specimens containing the deeply buried delamination only decreased by 14.01 MPa when the mode I toughness increased by 81.88%, and the specimen containing the surface delamination only decreased by 30.86 MPa when the mode II fracture toughness increased by 87.72%. However, improving the fracture toughness could not strengthen the specimens containing the through-width delamination. Moreover, a qualitative dynamic damage relationship, which described the relationship between delamination expansion and compression damage vividly, was proposed. The reason the increase of the toughness could improve the residual compression performance of the laminates containing delamination was that the higher fracture toughness hindered the secondary expansion of the delamination during the compression process so that the delamination area could almost remain unchanged.

Improvement of strength and toughness of 1 GPa Cu-bearing HSLA steel by direct quenching

A novel process based on recrystallization controlled rolled (RCR) + on-line direct quenching (DQ) and tempering (DQT) was developed to improve both yield strength and low-temperature toughness for 1 GPa Cu-bearing HSLA steel. Reheating quenching (RQ) and tempering (RQT) processes were compared to examine the effects of DQ and DQT on co-precipitation behavior of Cu-rich particles and Mo, V carbides. The evolution of microstructures under various heat treatments was characterized using optical microscope (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and X-ray diffraction (XRD). Tensile properties and low-temperature impact toughness were also tested. Differential scanning calorimetry (DSC) shows that lower activation energy of Cu precipitation in DQ steel than that in RQ steel. The lower activation energy can be attributed to higher density dislocations and finer martensitic laths, which results in high-density and finer Cu-rich particles formed in DQT steel. Meanwhile, the coarsening of Cu-rich particles in DQT steel is also inhibited resulting in the Cu-rich precipitates with ∼5.8 nm in DQ steel aging at 550 °C for 240 min. Subsequently, the precipitation of Mo, V carbides is promoted at the nucleation sites provided by the pre-precipitated high-density Cu-rich particles, with the rapid dissolution of cementite. Synergistic enhancement of yield strength and low temperature toughness has been achieved with a yield strength of 1056 MPa as well as impact energies of 204 J and 74 J at −40 °C and −85 °C, respectively.