Fabrication Of Stainless Steel Research Articles

Material extrusion-based fabrication of 316L stainless steel: analysis of debinding and sintering, mechanical properties, and corrosion resistance

Material extrusion-based fabrication of 316L stainless steel: analysis of debinding and sintering, mechanical properties, and corrosion resistance

Fabrication of superhydrophobic stainless steel via hybrid femtosecond laser-chemical method with wear-resistance and anti-corrosion properties

Fabrication of superhydrophobic stainless steel via hybrid femtosecond laser-chemical method with wear-resistance and anti-corrosion properties

Fabrication and Process Monitoring of 316L Stainless Steel by Laser Powder Bed Fusion with µ-Helix Scanning Strategy and Narrow Scanning Line Intervals

We first fabricated the single crystal of 316L stainless steel by laser powder bed fusion (L-PBF), focusing on the applicability of the µ-Helix scanning strategy with narrow pitch as a method for obtaining a single crystal. Various combinations of laser power and laser scanning speed were examined. The cubic block samples were orientated to <100> in the X-laser scanning direction, to <110> in the Y-laser scanning direction, and to <110> in the building direction, which is contrary to that obtained by the µ-Helix scanning strategy in electron beam melting (EBM), in which the X- and Y-laser scanning directions are orientated to <110>, and Z-direction is oriented to <100> direction. Also, it has been demonstrated that melt pool monitoring by on-axis and off-axis dual photodiodes can detect the nonequivalence of ±X-scanning and ±Y-scanning, which is responsible for the unexpected crystal orientation.

A Novel Method for the Fabrication of Antibacterial Stainless Steel with Uniform Silver Dispersions by Silver Nanoparticle/Polyethyleneimine Composites.

Only a few studies have so far focused on the addition of silver to SS316L alloys by conventional sintering methods. Unfortunately, the metallurgical process of silver-containing antimicrobial SS is greatly limited due to the extremely low solubility of silver in iron and its tendency to precipitate at the grain boundaries, resulting in an inhomogeneous distribution of the antimicrobial phase and loss of antimicrobial properties. In this work, we present a novel approach to fabricate antibacterial stainless steel 316L by functional polyethyleneimine-glutaraldehyde copolymer (PEI-co-GA/Ag catalyst) composites. PEI is a highly branched cationic polymer, which makes it exhibit very good adhesion on the surface of the substrate. Unlike the effect of the conventional silver mirror reaction, the introduction of functional polymers can effectively improve the adhesion and distribution of Ag particles on the surface of 316LSS. It can be seen from the SEM images that a large number of silver particles are retained and well dispersed in 316LSS after sintering. PEI-co-GA/Ag 316LSS exhibits excellent antimicrobial properties and does not release free silver ions to affect the surrounding environment. Furthermore, the probable mechanism for the influence of the functional composites on the enhancement of adhesion is also proposed. The formation of a large number of hydrogen bonds and van der Waals forces, as well as the negative zeta potential of the 316LSS surface, can effectively enable the formation of a tight attraction between the Cu layer and the surface of 316LSS. These results meet our expectations of designing passive antimicrobial properties on the contact surface of medical devices.

Porous Stainless Steel Microsphere Synthesis by a Nonconventional Powder Metallurgy Process Useful in the Cermet-Type Advanced Nuclear Fuel Fabrication

The fabrication of SS (stainless steel)-UO2 cermet-type advanced nuclear fuel pellets suitable for use in power reactors depends on the development of metallic (SS), ceramic (UO2), and cermet (SS-UO2) microspheres with special characteristics. In this work, a nonconventional powder metallurgy process was developed to produce porous SS microspheres aiming to contribute to solve the bottlenecks found in the SS-UO2 cermet pellet manufacturing. SS, UO2, and SS-UO2 microspheres and SS-UO2 cermet pellets were fabricated and characterized (XRD, EDX, EDS, and SEM). Hard (153 ± 5 µm; 132.2 ± 24.7 MPa; 72% TD) and soft (216 ± 10 µm; 1.3 ± 0.4 MPa; 17% TD) SS, hard (176 ± 6 µm; 147.4 ± 25.0 MPa; 99% TD) UO2, and cermet (SS-UO2) microspheres were obtained. The soft porous SS microspheres did not micronize properly in situ, but their high compressibility favors the compaction of the green SS-UO2 cermet pellet; in this pellet, the UO2 microspheres behaved as rigid inclusions. This favored the obtainment of sintered SS-UO2 cermet pellets with high geometric densities (93% TD), excellent metal–ceramic interaction, and the preservation of the physical integrity of the UO2 microspheres. The usage of high fractions of the SS-UO2 cermet microspheres obtained mixed with low fractions of the said soft porous SS microspheres is already under development. This will enable the fabrication of SS-UO2 cermet pellets with a volume fraction greater than 42 vol% UO2, a homogeneous distribution of UO2 microspheres in the metallic matrix, and null connection between them. The oxide–metal reduction mechanisms were discussed. The applicability of the process is already being explored in the manufacture of porous NdFeB microspheres.

Fabrication of a Flower-like Copper Oxide Film-Coated Nanoporous Stainless Steel Using Anodization-Assisted Electrodeposition as a Novel Antibacterial Material

In this study, flower-like copper oxide film was prepared on the surface of 316L nanoporous stainless steel (Cu/NPSS) by anodization-assisted electrodeposition. The prepared NPSS and Cu/NPSS were evaluated with Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and X-ray diffractometer (XRD). Based on local use of common diseases, the antibacterial activity of Cu/NPSS against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was investigated. The diameters of the as-formed nanopores were about 93 nm at 50 V. Cu film was successfully deposited on the surface of NPSS. The presence of Cu and O was detected in the surface of Cu/NPSS by EDX analyses. The results obtained for Cu/NPSS revealed a marked antibacterial ability. The growth inhibition rates of Cu/NPSS against E. coli and S. aureus were 99.6% and 97.4% within 12 h, respectively. This may be because of the small size and high surface-to-volume ratio of the material in addition to the release of metal ions in solution. Accordingly, Cu/NPSS will help broaden promising applications in fields of biomedical implants and devices.

Microstructural characteristics, mechanical properties and corrosion performance of super austenitic stainless steel 904L produced by wire arc additive manufacturing

This study involves the fabrication of a super austenitic stainless steel 904 L thin wall using wire arc additive manufacturing (WAAM) technology. The microstructure, mechanical properties, and localized corrosion performance of WAAM-processed 904 L were investigated. The average surface roughness varied between 22.43 and 28.51 µm due to the presence of delineations in the wall. Microstructural analysis revealed the presence of equiaxed, columnar, and elongated dendrites along the building direction (BD) of the as-deposited wall. Secondary phases were not noticed in the as-deposited wall due to repeated thermal cycles. Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed the uniform dissolution of elements such as Ni, Cr, and Mo within the austenitic matrix. The hardness mapping in WAAM 904 L indicated the variation at the top, middle, and bottom regions and was 220 ± 11 HV, 235 ± 9 HV, and 260 ± 8 HV, respectively. The tensile test outcomes of WAAM 904 L specimens at 0°, 45°, and 90° orientation showed lower anisotropy and observed maximum tensile properties in the horizontal direction (0 °), i.e., YS= 312 ± 12 MPa, UTS= 658 ± 24 MPa & %E = 36 ± 1.5%. The mode of fracture was ductile in nature, with dimples and microvoids. The Potentiodynamic polarization (PDP) tests in 3.5% NaCl solution highlighted the formation of stable passive film on the surface of the as-produced 904 L specimens, and superior resistance to pitting corrosion was noticed. Electrochemical impedance measurements revealed the stability of WAAM specimens and showed a similar trend to PDP outcomes. The degree of sensitization (DOS) of the WAAM 904 L samples was lower, and the corrosion rate ranged between 0.07 and 0.70 mils per year (mpy).

Effects of Hot Isostatic Pressing on the Properties of Laser-Powder Bed Fusion Fabricated Water Atomized 25Cr7Ni Stainless Steel

25Cr7Ni stainless steel (super duplex stainless steels) exhibits a duplex microstructure of ferrite and austenite, resulting in an excellent combination of high strength and corrosion resistance. However, Laser-Powder Bed Fusion fabrication of a water-atomized 25Cr7Ni stainless steel of novel chemical composition resulted in a purely ferritic microstructure and over 5% porosity. The current study investigated the effects of two hot isostatic pressing parameters on the physical, mechanical, and corrosion properties as well as microstructures of water-atomized 25Cr7Ni stainless steel of novel composition fabricated by L-PBF for the first time in the literature. The corrosion behaviour was studied using linear sweep voltammetry in a 3.5% NaCl solution. The Hot Isostatic Pressing-treated sample achieved over 98% densification with a corresponding reduction in porosity to less than 0.1% and about 3~4% in annihilation of dislocation density. A duplex microstructure of ferrite 60% and austenite 40%was observed in the X-Ray Diffraction and etched metallography of the HIP-treated samples from a purely ferritic microstructure prior to the HIP treatment. With the evolution of austenite phase, the HIP-treated samples recorded a decrease in Ultimate Tensile Strength, yield strength, and hardness in comparison with as-printed samples. The variation in the morphology of the evolved austenite grains in the HIP-treated samples was observed to have a significant effect on the elongation. With a reduction in porosity and the evolution of the austenite phase, the HIP-treated samples showed a higher corrosion resistance in comparison with the as-printed samples.

Fabrication and characterization of stainless steel 308 L / Inconel 625 functionally graded material with continuous change in composition by dual-wire arc additive manufacturing

Additive manufacturing (AM) technology can fabricate functionally graded materials (FGMs) with a layered gradient change in chemical composition and microstructure by changing the composition ratio of different filler materials layer by layer, which indeed have uneven and uncontrolled composition gradients between layers. In the present work, FGMs of stainless steel 308 L and Inconel 625, with continuous change in composition, were fabricated by dual-wire arc additive manufacturing (D-WAAM) by changing the speeds of dual wires in each single layer. The chemical composition, microstructure, phases, and mechanical properties of the FGM were investigated. The results showed that the composition gradient was smoothly distributed along the torch-travelling direction in each single layer, and the composition at the same position along the building direction was stable. With the increase in the content of Inconel 625, the austenite dendrites, which was the main microstructure, became finer first and then coarser, but there was no apparent abrupt change in microstructure in the gradient zone, which made the mechanical properties also show a smooth change. The mechanical properties were weak when the content of Inconel 625 was within 10–50 wt% due to the secondary phases (MC, Laves) distributed at the grain boundary. The proposed fabrication approach of FGM also showed advantages and flexibility in the design of gradient path, or the design of structure size if there is a requirement on the size in the building direction.

Fused filament fabrication and sintering of 17-4PH stainless steel

We demonstrate in this paper that Fused Filament Fabrication (FFF) is a reliable and rapid technology for manufacturing complex parts made with 17-4PH stainless steel. We printed, sintered, and evaluated the performance of FFF manufactured 17-4PH stainless steel. Our results show that FFF is competitive and even superior to other manufacturing technologies. It turned out that the mechanical properties are highly dependent on the post-treatment and hardening procedure. The elongation changed from 5 % − 9.5 % due to annealing treatments. We found yield strength of 1007 MPa, ultimate strength of 1212 MPa, and density > 99 % after hardening.

Ambient pressure fabrication of Ni-free high nitrogen austenitic stainless steel using laser powder bed fusion method

A novel one-step method for fabricating Ni-free high N austenitic stainless steel components at ambient pressure using metal nitride powders as the nitrogen source by the additive manufacturing technology of laser powder bed fusion (LPBF) is demonstrated. It exploits the rapid solidification conditions inherent to the LPBF process for the retention of N in solid solution instead of evaporation. A fully austenitic steel with a high N content of 0.87 wt% has been obtained. The solute strengthening induces more than 70% improvement in hardness and ~ 59% increase in yield strength compared to the LPBF fabricated SS316L and shows promising corrosion resistance. X-ray diffraction, X-ray photoelectron spectroscopy, electron backscattered diffraction were utilized to study the microstructures and relate them to the properties at multi-scales.

Fabrication of Austenitic ODS 316L Stainless Steel with Arc Plasma Sintering Method

Austenitic ODS (Oxide Dispersion Strengthened) 316L steel was fabricated using 316L SS (Stainless Steel) pre-alloyed powder and yttria powders by mechanical milling with APS (Arc Plasma Sintering) method. The powders were milled in High Milling Shaker at 1000 rpm in rotational speed for 10 hours at 10 BPR (Ball Powder Ratio). As milled powders were pressed at 20 Ton and sintered with APS for 0 to 12 minutes at 70 A. The samples were analysed using X-Ray Diffraction (XRD), Microscope Optic (MO) with micro-hardness tester and Scanning Electron Microscope – Energy Dispersive X-Ray Spectroscope (SEM-EDS). The results of phase and microstructure showed the austenitic grade of the samples. The sintering time contributed to the microstructure of the samples. At room temperature, the mechanical properties of ODS 316L SS was higher than conventional 316L SS.

Fabrication of Mo-Dispersed Type 304L Stainless Steel By Spark Plasma Sintering and Its Corrosion Resistance in 0.1 M NaCl

Stainless steels are widely used in industries because of their high corrosion resistance. The Cr-rich oxide film on the surface protects the balk metal. For type 316 stainless steel, 2~3 mass% Mo was added to improve corrosion resistance in chloride solutions. The pitting corrosion resistance of type 316 stainless steel is known to be higher than that of type 304 stainless steel1). The role of Mo has been investigated for long time. It was proposed that Mo forms Mo-oxides and inhibits corrosion attack2). In addition, it is suggested that Mo changes the structure of the Cr oxide layers on stainless steels 3).Spark Plasma Sintering (SPS) has been applied to fabricate various types of composite materials. The advantage of the SPS technique is rapid heating and cooling 4). When two metal powders were mixed and sintered, dual-phase materials are expected to be formed because sintering is conducted below the melting points of the metals.In this study, we fabricated Mo-dispersed type 304L stainless steel by spark plasma sintering, and the corrosion resistance was assessed in 0.1 M NaCl.Mo-dispersed type 304L stainless steel was fabricated by SPS. As the starting materials, pure Mo powders and type 304L stainless steel powders were used. Table 1 shows the chemical composition of type 304L stainless powders. Sintering was performed at 1373 K for 20 min. After sintering, the specimen was heat-treated at 1573 K for 5 h in vacuum and quenched in water. After that, the solution treatment was conducted at 1373 K for 30 min and water quenched. The specimen surface was polished down to 1 μm using a diamond paste. Sintered type 304L and type 316L were used as reference materials. The same SPS procedure and heart-treatments were applied to prepare those.The surface of Mo-dispersed type 304L was inspected using an optical microscope. Scanning electron microscope (SEM) was also used. Electron Probe Micro Analyzer (EPMA) analysis of surface was conducted.Potentiodynamic polarization curves were measured in 0.1 M NaCl solution (pH 6.0) at 298 K. Specimens were covered by epoxy resin, with the exception of the electrode area (5 mm × 5 mm).On the basis of the surface observations and X-ray diffraction, it was suggested that the steel matrix of Mo-dispersed type 304L is austenite, but many voids were generated. Mo-rich phase were observed on the entire surface. The size of Mo-rich phase was 100 ~ 200 μm. From EPMA analysis, the average concentration of Mo in Mo-rich phase was determined to be 4.3 mass%. In the steel matrix, the average Mo concentration was 2.8 mass%.In polarization measurements in 0.1 M NaCl, the passive current density of Mo-dispersed type 304L and type 316L was unstable, probably because of the presence of voids. However, the pitting potentials of Mo-dispersed type 304L were found to be higher than those of type 316L. The selective dissolution of Mo-rich phases was thought to prevent the initiation of pitting effectively in chloride environments.References; Nishimoto, I. Muto, Y. Sugawara, N. Hara, J.Electrochem.Soc., 166 (11), C3081-C3089 Hashimoto, K. Asami, K. Teramoto, Corros. Sci., 19 (1979), 3-14. F. Montemor, A. M. P. Simões, M. G. S. Ferreira, M.D.C. Belo, Corros. Sci., 41 (1999), 17-34.Omori, Mater. Sci. Eng., A287 (2000), 183-188. Figure 1

Fabrication of nanocrystalline austenitic stainless steel with superior strength and ductility via binder assisted extrusion method

Biomedical austenitic stainless steel (ASTM F2581) has been processed by the powder metallurgy technology using binder assisted extrusion method and aside a sintering aid. The resultant microstructure was examined by optical microscopy, field emission scanning electron microscopy, transmission electron microscopy and x-ray diffraction methods. The optical microscopy images indicate that using the binder and sintering aid considerably decreases the porosities of the sintered samples. The x-ray diffraction and transmission electron microscopy images reveal that the microstructure of the sintered alloy consists of austenite in nanocrystalline form and amorphous phases. The mechanical properties were measured through compressive tests. The mean yield strength is estimated at about 824 MPa, and the compressive strength exceeds 1GPa, which is superior to the austenitic stainless steel produced through the conventional methods. Furthermore, the process followed here is compatible with large scale industrial production at a reasonable cost.

Statistical Review of Microstructure-Property Correlation of Stainless Steel: Implication for Pre- and Post-Weld Treatment

For the past three centuries, there has been a very high demand for stainless steel for different applications, due to its corrosion resistance coupled with the good strength and low cost of the metal. Several welding techniques have been adopted in the fabrication of stainless steel, with the choice of welding technique hinged on the desired requirements. Advancement has been made in its dissimilar welding with other metals like aluminum, copper and titanium. While similar welding of stainless steel faces the challenge of weld metal property deterioration, dissimilar welding poses more serious challenges due to the differential in chemical composition and the thermophysical properties of the base metals. A review of the literature reveals that considerable progress has been made in the improvement of the properties of the weld joint by the application of several weld treatment processes. It was discovered that most of the researchers focused on the effect of these weld treatment processes on the properties of the weld joints, with little attempt to establish a relationship between the microstructure and properties. This review paper critically analyzed the effect of weld treatment processes on the properties of stainless steel in light of microstructure-property correlation.

Structural characterization and nanoindentation studies on mechanical properties of spark plasma sintered duplex stainless steel nanocomposite

Nano-sized titanium nitride (TiN) powders were used as reinforcements for the fabrication of duplex stainless steel (SAF 2205) via spark plasma sintering (SPS) route. Optimized parameters of 1150 °C temperature, 100 °C/min heating rate, 50 MPa pressure and 15 min holding time were utilized for sintering of the SAF 2205-TiN composite. SEM equipped with an EBSD and TKD detectors were used to gain insight into sintered composite microstructures and grain boundary character. XRD was used to study crystallinity and phase transformation. The discrete mechanical properties of ferrite/austenite grains and grain boundaries were studied using nanoindentation technique. The addition of TiN nanoparticles resulted in decrease of the α-Fe peaks with principal planes shifting from α-Fe (110) to γ-Fe (111). The EBSD confirmed that the addition of TiN nanoparticles to duplex stainless steel could initiate and advance ferrite to austenite phase reverse transformation. The TKD confirmed that nanosized nitrides are concentrated at the ferrite/austenite interface. The nanoindentation studies showed that the nano-hardness (H), elastic modulus (E), plasticity index (Ψ), and anti-wear properties were improved with the TiN nanoparticle addition from 0 to 8 wt%.

Fabrication of 316L stainless steel with TiN addition by vacuum laser powder bed fusion

Fabrication of 316L stainless steel with TiN addition by vacuum laser powder bed fusion

Optimization of the 3D Printing Parameters for Tensile Properties of Specimens Produced by Fused Filament Fabrication of 17-4PH Stainless Steel.

Fused filament fabrication (FFF) combined with debinding and sintering could be an economical process for three-dimensional (3D) printing of metal parts. In this paper, compounding, filament making, and FFF processing of feedstock material with 55% vol. of 17-4PH stainless steel powder in a multicomponent binder system are presented. The experimental part of the paper encompasses central composite design for optimization of the most significant 3D printing parameters (extrusion temperature, flow rate multiplier, and layer thickness) to obtain maximum tensile strength of the 3D-printed specimens. Here, only green specimens were examined in order to be able to determine the optimal parameters for 3D printing. The results show that the factor with the biggest influence on the tensile properties was flow rate multiplier, followed by the layer thickness and finally the extrusion temperature. Maximizing all three parameters led to the highest tensile properties of the green parts.

Effect of preheat temperature and post-process treatment on the microstructure and mechanical properties of stainless steel 410 made via ultrasonic additive manufacturing

Ultrasonic additive manufacturing (UAM) is a solid-state manufacturing technology for producing near-net shape metallic parts combining additive ultrasonic metal welding and subtractive machining. Even though UAM has been demonstrated to produce robust metal builds in Al–Al, Al–Ti, Al-steel, Cu–Cu, Al–Cu, and other material systems, UAM welding of high strength steels has proven challenging. This study investigates process and post-processing methods to improve UAM steel weld quality and demonstrates the UAM fabrication of stainless steel 410 (SS 410) builds which possess, after post-processing, mechanical properties comparable with bulk material. Unlike UAM fabrication of softer metals, this study shows that increasing the baseplate temperature from 38∘C (100∘F) to 204∘C (400∘F) improves interfacial strength and structural homogeneity of the UAM steel samples. Further improvement in strength is achieved through post-processing. The hot isostatic pressing (HIP) post treatment improves the shear strength of UAM samples to 344 MPa from 154 MPa for as-welded samples. Microstructural analyses with SEM and EBSD show no evidence of body centered cubic (BCC) ferrite to face centered cubic (FCC) austenite transformation taking place during UAM welding of SS 410. The weld quality improvement of UAM steel at higher baseplate temperatures is believed to be caused by the reduction of the yield strength of SS 410 at elevated temperature. HIP treatment is shown to increase the overall hardness of UAM SS 410 from 204 ± 7 HV to 240 ± 16 HV due to the formation of local pockets of martensite. Nanohardness tests show that the top of layer n is harder than the bottom of layer n+1 due to grain boundary strengthening.

Fabrication of stainless steel 316L/TiB2 composite coating via friction surfacing

Stainless steel 316L/TiB2 composite coatings were fabricated with different TiB2 contents using friction surfacing (FS) on the stainless steel 304 substrate. One or two blind holes were drilled at different positions axially on the cylindrical 316L consumable rods for keeping micron-size TiB2 powder as the reinforcement in the coatings. After FS, TiB2 was found to be embedded into the austenitic matrix and also partially decomposed leading to the formation of FeB2 and FeTi under high temperature and high strain rate. Compared with the friction-surfaced (FSed) 316L coating, the grain size of austenite in the TiB2 reinforced composite coating was refined from 7.8 to 0.64 μm, where austenite grains closed to {111} tends to transform to FeTi. Compared with monolithic 316L coating, the hardness of the FSed 316L/TiB2 coating was significantly increased from 219 to 1056 HV0.2 owing to the presence of TiB2 and intermetallic phases, finer austenitic grains and higher misorientation density. The pitting corrosion resistance of the FSed 316L coating was improved due to the elimination of MnS inclusions whereas the FSed 316L/TiB2 coating possessed lower pitting resistance due to the presence of FeTi. Moreover, the passivity of the 316L/TiB2 coating in 3.5% NaCl solution was preserved but the capability of re-passivation was degraded.