Stainless Steel Samples Research Articles

High-Resolution Infrared Reflectance Distribution Measurement Under Variable Temperature Conditions

The bidirectional reflectance distribution function (BRDF) can effectively characterize the reflectance properties of a target, which can be used to correct infrared remote sensing data and improve the accuracy of remote sensing measurements. When the surface temperature changes, the reflectance characteristics of the target usually change, and it is necessary to carry out BRDF measurements under variable temperature conditions. In this paper, a variable-temperature infrared BRDF measurement system based on a robotic arm is developed to realize high-resolution wide-temperature region measurement of BRDF. To improve the measurement accuracy, the shaping optical path was used to expand the laser beam, combined with the laser level to accurately adjust the three-dimensional coordinates of the robotic arm, and the dichotomy method is used to calibrate the detector nonlinearly. A portable heater suitable for the mechanical arm corner mechanism is developed, and fast and high-precision temperature control is realized by proportional integral derivative (PID) control. The specular and diffuse BRDF distributions were measured at room temperature to verify the effectiveness of the system. The BRDF distribution of SUS314 stainless steel samples with different roughness is measured during two temperature increases from 20 °C to 1000 °C, and the changing rule of BRDF under variable temperature environment is summarized, which provides technical support for evaluating the optical properties of high-temperature materials and improving the measurement accuracy of remote sensing data.

Research on mechanical property degradation model of equipment compartment floor under atmospheric corrosion condition

A mechanical property degradation model of material fatigue life varying with stress level and corrosion time was developed in this study. An acidified NaCl solution was used to accelerate the corrosion of stainless-steel samples, and the relationship between laboratory-accelerated corrosion and atmospheric corrosion was established using corrosion thickness loss parameters. Based on the results of a pre-corroded fatigue test, lgN–S–T surface models and a modified version of Miner’s rule for calculating nonlinear mechanical damage accumulation were proposed. Taking a real part of a high-speed train as an example, critical operating mileages considering material fatigue performance degradation under corrosion conditions were calculated, which were consistent with failure mileages of the census results.

Characterization of novel 3D-printed metal shielding for brachytherapy applicators.

To characterize 3D-printed stainless steel metal samples in the presence of an Iridium-192 source for organ-at-risk sparing in gynecologic brachytherapy. Samples of 3D-printed stainless steel (5.5×5.5 cm2, thickness range 1-5mm) were embedded in a solid water phantom at varying distances from source catheters. An Ir-192 brachytherapy source was passed through the phantom and the dose was measured using EBT3 Gafchromic film. The film was initially positioned in the sagittal plane 2cm away from the catheters, with the metal directly below and then 1cm from the film. A uniform dose was delivered at the film plane. A second setup measured a depth dose curve in solid water with film in the transverse plane directly above the metal samples. This setup was recreated using Monte Carlo simulations (EGSnrc egs_brachy). Validation between methods was performed with unshielded (solid water only) measurements. The planar dose passing through the metal samples (thickness 1-5mm) at the midpoint between the film and catheters, decreased compared to solid water by 7.4%±6.9% to 26.5%±5.5%. Dose enhancement on the order of 5% was noted when metal was directly adjacent to the film. The average decrease in depth dose from a single dwell position ranged from 10.0%±5.9% (1mm) to 21.1%±5.3% (5mm) as measured with film, and from 3.8%±0.9% (1mm) to 16.3%±0.9% (5mm) using MC simulation. The average depth dose values were measured using a line width of 2.5mm for film, and 3mm for MC simulation, and the measurements generally agree within standard error. The 3D-printed metal samples show potential for personalized applicators. Maximum dose reduction of 26.5%±5.5% compared to solid water was measured at 2cm from the source using the 5mm sample. An outer layer of solid water could potentially be used to reduce dose enhancement due to increased scatter near the metal.

Influence of Multiple Repair Welding on Microstructure and Properties of 06Cr19Ni10 Stainless Steel

AbstractRepair welding technology is widely used in the manufacturing and maintenance of rail transit equipment to repair welding defects. However, repair welding induces modifications in joint performance, and it is necessary to study the microstructure evolution behavior to reveal the reasons. In this study, the effects of multiple repair welding on the microstructure, mechanical, and fatigue properties of 06Cr19Ni10 stainless steel samples were studied. The surface texture and fracture morphology analyses of the samples were conducted by optical microscopy (OM), scanning electron microscopy (SEM), and its equipped backscattered electron diffraction (EBSD) technique. The mechanical and fatigue properties of the samples with different repair welding times were further obtained by hardness, tensile, and fatigue tests. The results show an increase in the grain size and the substructure content in the heat-affected zone (HAZ), and the austenite orientation is changed, attributable to multiple repair welding. Multiple heat inputs result in a significant increase in hardness from 165 HV to 185 HV, a noticeable decrease in tensile strength and elongation, and an upward trend in yield strength. Under the constant stress level, the heat input of multiple repair welding causes a decrease in the fatigue life and significantly reduces toughness in the instantaneous fracture zone of the secondary repair sample.

Investigation of pitting corrosion of 304L stainless steel in algerian manufacturing

Stainless steel structures are subjected to gradual deterioration of their fundamental qualities when subjected to both mechanical stress and harsh conditions. The objective of this work is to examine the influence of tension-induced cold deformation on the localized roughness corrosion of 304L steel in a 3% NaCl solution, which mimics the conditions of saltwater. The samples underwent corrosion testing using standardized and deformed tensile specimens of algerian industrial manufacturing at different deformation rates: 2.18%, 3.63%, 10.90%, and 16.36%. The results, which encompassed corrosion susceptibility, pitting tendencies, and repassivation potentials, were compared and examined in relation to the deformation rate. The findings suggest that when the deformation rates increase, all of these potentials decrease, except for the roughness potential, which shows a considerable decrease. This decline indicates a reduction in the material's ability to resist corrosion. The main reasons why stainless-steel samples exposed to the phenomenon of corroded pits fail in Algerian industrial manufacturing are directly related to their resistance and strength characteristics, which in turn affect the mechanical behavior of 304L steel and its electrochemical behavior in aggressive solutions.

Mass finishing of additively manufactured AISI 316L using pecan nutshells as sustainable abrasive media

Abrasive processes represent the main methods for obtaining high-quality surface finish in metal parts. As one main characteristic, these processes have a relatively high consumption of energy per material volume removed, as well as many inputs, such as abrasive tools and equipment, and, consequently, a high associated environmental impact. Additive manufacturing is becoming a competitive method to produce customized parts, but the surface finish is often not good enough for the application, and post-processing is needed. In this work, a mass finishing process using a planetary mill with abrasive media made of sustainable materials (pecan nutshells) was used on AISI 316L stainless steel samples manufactured by selective laser melting (SLM). The main goal was to perform a multicriteria analysis of the sample surface before and after post-processing. Through the analysis, it could be observed that the nutshell abrasive media has results close to those of traditional ceramic media. The increase in the rotation speed of the planetary mill, increase of finishing time, and use of abrasive pastes can further increase the effectiveness of the process.

Thermal Conductivity of 3D Printed Metal using Extrusion-based Metal Additive Manufacturing Process

Abstract In this study, the thermal conductivity of 3D-printed 316L stainless steel parts using the bound metal deposition (BMD) method, an extrusion-based 3D printing technology, were examined experimentally and validated numerically using finite element analysis (FEA). Various critical printing parameters were examined, including infill density, skin overlap percentage, and print sequence to study their effect on the printed thermal conductivity. A heat conduction experiment was performed on the 3D-printed samples of 316L stainless steel followed by a FEA. The results from this investigation revealed that an increase in 3D printing infill density correlated with a rise in effective thermal conductivity. Conversely, a substantial decrease in thermal conductivity was observed as porosity increased. For instance, at a porosity level of 16.5%, the thermal conductivity experienced a notable 33% reduction compared to the base material. The skin overlap percentage, which governs how much the outer shell of adjacent layers overlaps, was found to impact heat transfer across the overall part surface. A higher overlap percentage was associated with improved thermal conductivity, although it could affect the surface finish of the part. Furthermore, the study explored the print sequence, focusing on whether the outer wall or infill was printed first. Printing the outer wall first resulted in higher thermal conductivity values than that obtained from printing the infill first. Therefore, it is crucial to carefully consider these factors during the BMD 3D printing process to achieve the desired thermal conductivity properties.

Deep Learning-Driven Prediction of Mechanical Properties of 316L Stainless Steel Metallographic by Laser Powder Bed Fusion.

This study developed a new metallography-property relationship neural network (MPR-Net) to predict the relationship between the microstructure and mechanical properties of 316L stainless steel built by laser powder bed fusion (LPBF). The accuracy R2 of MPR-Net was 0.96 and 0.91 for tensile strength and Vickers hardness predictions, respectively, based on optical metallurgy images. Feature visualisation methods, such as gradient-weighted class activation mapping (Grad-CAM) and clustering, were employed to interpret the abstract features within the MPR-Net, providing insights into the molten pool morphology and grain formation mechanisms during the LPBF process. Experimental results showed that the optimal process parameters-190 W laser power and 700 mm/s scanning speed-yielded a maximum tensile strength of 762.83 MPa and a Vickers hardness of 253.07 HV0.2 with nearly full densification (99.97%). The study marks the first application of a convolutional neural network (MPR-Net) to predict the mechanical properties of 316L stainless steel samples manufactured through laser powder bed fusion (LPBF) based on metallography. It innovatively employs techniques such as gradient-weighted class activation mapping (Grad-CAM), spatial coherence testing, and clustering to provide deeper insights into the workings of the machine learning model, enhancing the interpretability of complex neural network decisions in material science.

A comprehensive study on the microstructure evolution and mechanical property characterization of selective laser melted 18Ni300 stainless steel during heat treatment processes

The influence of different heat treatment processes on the microstructure and mechanical properties of 18Ni300 stainless steel manufactured by selective laser melting has been investigated in the present study. The microstructures, nanoprecipitates, and mechanical properties of the differently heat-treated samples were analyzed using various precision instruments. Compared with a non-treated 18Ni300 stainless steel sample, the results showed that the microstructure was mainly composed of fine lath-like martensite, with a large number of nano-precipitates dispersed both within the martensite and in the boundaries. In addition, there was a preserved amount of austenite between the lath-like martensite and the spherical nanoprecipitate in the SAT sample. The interactions between the martensite matrix and the nanoprecipitates and dislocations were assumed to be the main reason for the high strength of 18Ni300 stainless steel. These precipitates included rod-shaped or needle-shaped, Ni3Ti, Ni3Mo, and Ni3(Ti, Mo) nano-precipitates, as well as spherical Ti–Al nano-oxidized precipitates and massive Ni-rich precipitates. The shear and by-pass mechanisms between the strengthened nano-precipitate and the dislocations were found to depend on the size of the nanoprecipitate. The influence of the nanoprecipitation on the indentation hardness became more evident after heat treatment, but the effect on the indentation modulus was not that obvious. The AT- and SAT-treatments significantly improve the strength, hardness, and modulus of samples but were found to reduce the toughness and plasticity. After the AT- and SAT-treatments, the protrusions became smaller, and the small isometric protrusion of a shear lip became significantly smaller than for the as-built material.

Non-contact mechanical Q-factor measurement system based on electromagnetic acoustic transducer

The mechanical quality factor (Q-factor), which is the reciprocal of the vibration loss constant, is one of the most important parameters in vibration engineering; however, there are no methods for its precise measurement. Q-factor databases are thus commonly used. This study proposes a completely non-contact measurement system for the Q-factor that combines non-contact excitation (achieved using an electromagnetic acoustic transducer) with non-contact support (achieved using near-field ultrasonic levitation based on two Langevin transducers). The proposed method was used to measure the Q-factor for a stainless steel (SUS304) sample (thin cylindrical rod with a diameter of 1.5 mm and a length of 80 mm)and a duralumin (A2017). The 5 times average Q-factor was 2010 with standard deviation of 50 for stainless steel (SUS304), and 49,000 with standard deviation of 3900 for duralumin (A2017). The proposed method also allowed for the measurement of Young’s modulus, resulting in 217.17 ± 0.34 GPa for stainless steel (SUS304), and 71.39 ± 0.20 GPa for duralumin (A2017).

Evaluation of Passive Films on 17-7PH and 410 Stainless Steel Exposed to NaCl Solution.

This work covers the formation of a passive state for two different alloys used in the aeronautical industry. The aim of this study is to investigate the effectiveness of passivation treatments on 17-7PH and 410 SS (stainless steel) samples, specifically when performed with citric and nitric acid solutions at 49 °C using an immersion time of 90 min and subsequent exposure in 3.5 wt.% NaCl solution. Employing the cyclic potentiodynamic polarization (CPP) technique, the corrosion properties of the passivated material were evaluated according to the ASTM G65-11 standard. A microstructural analysis was performed using scanning electron microscopy (SEM). The passivated layer was characterized via X-ray photoelectron spectroscopy. In the results, the CPP curves showed positive hysteresis, indicating pitting localized corrosion, and 17-7PH steel passivated at 49 °C for 90 min in citric acid exhibited lower corrosion rate values equivalent to ×10-3 mm/year.

Microstructure and mechanical properties of 316L stainless steel manufactured by multi-laser selective laser melting (SLM)

The microstructure and mechanical properties of 316L stainless steel samples manufactured by dual-laser selective laser melting technology, were investigated in compare with that of the single-laser scanning samples. It was found that the porosity of the dual-laser overlap samples was lower than that of single laser forming samples due to the different laser energy density absorbed by the powders. Furthermore, it was found that the crystal structure and crystal orientation of both zones were similar. From the TEM observation, it was noted that the number density of nano-oxides in the overlap zone was higher than that in the single laser forming zone. This reason was suggested as the difference of the oxygen content inside the melt pool during the forming process. The strength and microhardness of the single-laser samples was lower than that of the dual-laser overlap samples, but the elongation was higher. By analyzing the strengthening mechanism, it was revealed that Orowan strengthening was the main reason for the difference. These results could guide the large-size component manufactured using the muti-laser selective laser melting technology.

Influence of print-chamber oxygen content on the microstructure and properties of 3D-printed 316L

Abstract Samples of 316L stainless steel have been prepared using laser-powder bed fusion from the same batch of powder using different print-chamber oxygen levels, ranging from 50 ppm to 1500 ppm. The oxide particle density is found to increase with oxygen content, while the cell structure is invariant with oxygen level and the grain size shows a relatively sharp transition for measured oxygen levels of above 450 ppm. Based on the microstructural observations it is suggested that the increasing oxygen levels leads to a transition in the solidification pattern. Samples printed at the higher oxygen level show higher strength and lower mechanical anisotropy than samples with a coarser grains structure printed at lower oxygen levels. The main influence of the higher oxide particle content on thermal stability is on the kinetics of recrystallization during isothermal annealing at 1000 °C.

Influence of synchronous-hammer-forging intervention temperature on the microstructure and properties of 316L components fabricated by laser directed energy deposition

Synchronous-hammer-forging has been proved to be an effective method to control the microstructure and properties of metal components in additive manufacturing, but the influence of the intervention temperature is still unclear. 316L stainless steel samples with different hammer-forging intervention temperature were prepared by laser directed energy deposition (LDED) technology. The results show that due to dynamic recrystallization and dislocation accumulation effect, the grain size of the component decreases first and then increases with the increase of hammer-forging temperature, while the dislocation density and tensile strength increase first and then decrease.

Microstructural Optimization and Corrosion Resistance Enhancement of Austenitic 317L Stainless Steel through Tailored Heat Treatment

Austenitic 317L stainless steel was favored in many industrial applications due to its excellent corrosion resistance and mechanical properties. The study involved heat treating Austenitic 317L stainless steel samples at temperatures of 500℃, 950℃, and 1100℃ to explore the effects of heat treatment temperature on microstructure and corrosion resistance. Electrochemical analysis showed that the 317L sample treated at 1100℃ exhibited the lowest passive current density, indicating the best improvement in corrosion resistance at this temperature. Results from corrosion weight loss experiments confirmed that the least weight loss occurred under the heat treatment conditions of 950℃ and 1100℃, suggesting enhanced corrosion resistance of the material. Microstructural characterization revealed that after heat treatment at 950℃, the metallographic structure transformed from a complex, irregular size and chaotic growth pattern to uniformly grown and comparatively equal-sized metallographic structures. Furthermore, heat treatment at 1100℃ resulted in larger metallographic structures with reduced boundary width and distribution density. Consequently, enhanced corrosion resistance was observed at both temperatures. Based on these findings, a heat treatment range of 950℃ to 1150℃ appeared to be a suitable post-processing method for optimizing the microstructure of 317L while concurrently improving its corrosion resistance.

A cryogenic forced oscillation apparatus to measure anelasticity of ice.

We have developed a new cryogenic uni-axial forced oscillation apparatus to measure the anelastic behavior of ice by adapting the design of a previous high-precision apparatus for use in low-temperature (<0 °C) conditions. With this new apparatus, Young's modulus and attenuation can be measured over a broad frequency range from 10-4 to 10Hz. We have performed calibration tests with standard materials (steel spring, stainless steel, and acrylic samples) under various conditions to assess the apparatus properties and correct the effects on the obtained raw data. Young's modulus and attenuation for an acrylic sample after all of the data corrections show good agreement with previously published values, demonstrating the validity of the data corrections and reliability of the obtained data. We further obtained a preliminary dataset of Young's modulus and attenuation for an ice polycrystalline sample under small median stress and small stress amplitude. The anelastic response was not strain amplitude-dependent, that is, the response is linear. Moreover, the attenuation data are consistent with the data measured for other polycrystalline materials under similarly small stress conditions in terms of the Maxwell frequency scaling, which is known as a scaling law applicable to linear anelasticity induced by the diffusionally accommodated grain boundary sliding mechanism. Although there is still room for improving the control of testing conditions, we show that the new forced oscillation apparatus is capable of systematic studies on the anelastic properties of ice, the subject of future studies.

Elevated temperature rusting characteristics of UNS 31254 weldments within the operational confines of fossil fuel-fired plants and municipal waste incinerator surroundings at 700 °C

ABSTRACT This study investigates the air oxidation and rusting traits of fully austenitic alloy 254 stainless steel samples at 700°C after pulse current gas tungsten arc welding (PCGTA) and CO2 laser beam welding (CO2 LBW), with or without molten salt, relevant to coal-fired plants and waste incinerator settings. Among the weldments studied, CO2 laser weldments demonstrate greater resilience to corrosive gas and salt amalgamation, as well as air oxidation, compared to gas tungsten arc weldments, possibly due to thermal disparities and microstructural differences inherent in the welding processes. Protective oxides enhance corrosion resistance in air-oxidised samples, while corrosive compounds like CrS, Cr2K2O7, etc., reduce corrosion resistance and promote spallation in salt-degraded material. A thermogravimetric approach was used to assess rusting effects, alongside microstructural analysis employing optical, Scanning electron microscopy/ Energy dispersive x-ray spectroscopy (SEM/EDS), and X-Ray diffraction analysis (XRD) techniques.

Measuring Dielectric Properties of MARDI 76 (MRQ76) Rice at the Frequency of 915 MHz and 2.45 GHz

The microwave heating system has been widely used in the food processing and postharvest handling of rice. However, to develop efficient heating energy for the heating and drying process, the knowledge of permittivity or dielectric properties of the MARDI 76 (MRQ76) rice is quite important. The penetration and power dissipation of microwave inside the MARDI 76 (MRQ76) rice is strongly dependent on its dielectric properties or permittivity. Furthermore, characterisation of changes in permittivity or dielectric properties of MARDI 76 rice at elevated temperatures is essential for designing the microwave heating device and system. The permittivity or dielectric properties of MARDI 76 rice (MRQ76) were measured using Agilent open-ended coaxial-line probe and Agilent E5071C Network Analyser. The temperature of the MRQ 76 rice sample was regulated using a WiswCircu Circulator Water bath between temperatures of 27ºC to 70ºC. MARDI MRQ 76 rice sample was placed into the temperature-controlled stainless steel sample holder with water jacket assembly which was designed for permittivity measurement at different temperatures. The effect of temperature on dielectric properties of MARDI 76 rice, power dissipation and penetration depth of microwave radiation at the Industrial, Scientific, and Medical (ISM) heating frequency of 915 MHz and 2.45 GHz was assessed. Results indicated that both dielectric constant and dielectric loss of MARDI 76 rice samples increased with increasing temperature. Power dissipation of microwave radiation inside MARDI 76 rice increases with an increase in temperature. On the other hand, the penetration depth of microwave radiation into the MARDI 76 rice decreased with the increase in temperature. The result of this study shows dielectric properties and heating temperature of MARDI MRQ 76 rice play an important role in designing the microwave heating system for MARDI MRQ 76 rice.

A novel powder sheet laser additive manufacturing method using irregular morphology feedstock

Irregular (i.e. non-spherical) morphology powder is more cost-efficient to produce than spherical shaped powder. However, its reduced levels of flowability limit the wide application ranges of laser beam powder bed fusion (LPBF). To address this issue, a novel powder sheet additive manufacturing concept (MAPS) is proposed. Herein, a pre-manufactured metal particle-polymer binder composite (i.e. powder sheet) feedstock is employed as a raw material. The printability of irregularly shaped powder particles in sheet (MAPS) format was physically investigated using a range of different process parameters. The manufacturing process was observed by high-speed imaging. Microstructural and chemical element characterisations of the irregularly shaped powder particle print were then compared against those prints which were conducted using sheet-based (MAPS) spherical powder morphologies. The results indicated that the geometric accuracy and density of irregular powder morphology sheet printing improved when using a negative defocus strategy of the laser beam. A negative defocusing strategy allowed for the melting mode of the material to be transformed from keyhole to a more favourable conduction state. High speed imaging revealed that more spatter and vapour plume were observed with the increase in the magnitude of the negative defocus. The multi-morphology 304 L stainless steel (SS304) samples were printed in a single printer using an efficient method for the first time, i.e. printing spherical SS304 material on top of irregular SS304. EDX results indicated an insignificant change of chemical elements between the spherical and irregular prints. EBSD results revealed that columnar grains could grow through the irregular-spherical transition zone and similar grain size can form between spherical and irregular prints. The results of this study provide insights into the optimum printing configurations for powder sheet additive manufacturing using a cost-effective solution of irregular morphology material.

Tribological behavior evaluation of poly-ether-ether-ketone (PEEK) in dry journal bearing on shaft wear test

This paper investigated the tribological behavior of pure PEEK playing as a dry journal bearing, sliding against stainless steel, under real-life operating conditions in a wear test lasting 2 h. Four conditions were carried out with different magnitudes of normal load and sliding speed, while keeping a constant PV parameter. Sample topography assessments were performed with scanning electron microscopy and white light interferometry techniques. In addition, PEEK samples were also evaluated by Fourier Transformed Infrared Spectroscopy and thermal analyses by Differential Scanning Calorimetry. The coefficient of friction (COF) changed throughout the wear test and exhibited a running-in period followed by a transition, with an increase of COF, and then a tendency to reach a steady-state. Moreover, the COF behavior obtained suggests that there was an influence of the wear test parameters, mainly right after the running-in period — and the COF averages for the steady-state period were statistically equal. Stainless steel samples showed mild wear, while PEEK samples had a drastic alteration of their topography imposed by the wear test — including an increase in its degree of crystallinity. Nonetheless, the PEEK journal bearing samples did not fail from wear and their mass losses were small. Polymeric wear particles were generated and were found weakly adhered to both the body and the counter body. PEEK exhibited a lumpy transfer process — nonetheless, SEM images evaluation was useful to verify that these particles were eventually merged during sliding, and kneaded in the convex-concave contact, which provided them a film-like appearance. Furthermore, adhesive and abrasive wear mechanisms were identified, which were shown to be related to the journal bearing on shaft wear test arrangement.