Search

17–7 PH stainless steel is a highly versatile material with a multitude of applications in a diverse range of fields, including aerospace, chemistry and petrochemistry, and medicine. The material's exceptional mechanical properties and corrosion resistance render it the optimal selection for numerous components and instruments. Nevertheless, the surface properties of 17–7 PH stainless steel are inadequate for applications requiring high hardness and wear resistance in certain extreme environments. Due to its excellent mechanical properties and corrosion resistance, it can be utilized in the manufacturing of pharmaceutical equipment components. However, certain specialized environments still require surface nitriding treatment. Considering the complex heat treatment process required for this material, this paper reports a detailed study of the surface performance changes of 17–7 PH steel before and after ion nitriding following aging heat treatment. The study employs rolled 17–7 PH stainless steel as the subject material. The impact of heat treatment on plasma nitriding of stainless steel is investigated by comparing and analyzing the influence of martensite content and dislocation density within the martensite of the material prior to and following heat treatment on the hardness, thickness, and corrosion resistance of the nitrided layer on the surface of the steel after nitriding. The results demonstrate that 17–7 PH stainless steel, which does not undergo heat treatment, exhibits a high internal dislocation density, a high nitriding efficiency, and consequently, a high surface hardness. Following the application of a heat treatment, there is an increase in the martensite content of 17–7 PH stainless steel, a decrease in the dislocation content, and an increase in the matrix hardness. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing is revolutionizing how we produce and use materials. Selective Laser Melting (SLM) is one of the most popular additive manufacturing techniques for creating high-performance metal components. Stainless Steel is preferred for additive manufacturing due to its powder form availability, low cost, mechanical properties, and corrosion resistance. However, the complex thermal history and rapid solidification in the SLM process led to an out-of-equilibrium microstructure of resulting components, which can affect their mechanical properties. To better understand the relationship between processing, microstructure, and properties, exploring and enhancing SLM-fabricated stainless-steel components is essential. This review comprehensively overviews the selective laser melting process, key processing parameters, and commonly encountered defects. Furthermore, the study presents a detailed discussion of microstructure, mechanical behavior (including hardness, tensile, and fatigue properties), and corrosion resistance of all SLM-manufactured stainless steel grades, along with the effects of various post-process treatments. This paper reveals that the SLM process can produce stainless steel with satisfactory performance that may exceed conventionally processed materials. However, the final section highlights the challenges and research gaps in this field that must be addressed. [ABSTRACT FROM AUTHOR]

This paper utilizes the plasma arc as the heat source to successfully fabricate well-formed thin-walled parts using combined cable wire duplex stainless steel 2209. Microstructure of parts exhibited the favorable two-phase ratio and the absence of σ-phase. It was found that appropriate heat input (1.68 kJ/cm) and cooling rate (5 °C/s) can effectively avoid the precipitation of σ-phase. Furthermore, the properties of the as-deposited samples were comparable to those of the samples heat-treated at 1300 °C, proving that no subsequent heat treatment was required for 2209 stainless steel fabricated by plasma arc additive manufacture. The samples showed excellent properties, in which the ultimate tensile strength and yield strength were improved by about 7% and 24% compared with GB/T4237-2015. The impact toughness meets the requirements of EN10028-7-2016, which is about 35% higher than that of the cold metal transfer samples, and the corrosion resistance is comparable to that of hot rolled 2205. [ABSTRACT FROM AUTHOR]

304 stainless steel demonstrates a low thermal conductivity and work hardening characteristics, resulting in its processing, and will adhere to the tip of the tool; as well as the phenomenon of chipping, shortening the life of the tool. AlTiN coatings are representative of coatings applied to carbide tools. In this paper, AlTiN coatings with different arc current processes were deposited on carbide milling inserts using arc ion plating. The microstructure, mechanical properties, and milling properties of the coatings were investigated by using the SEM, EDS, XRD, scratch meter, friction and wear meter, and vertical machining center. The findings revealed that all coatings displayed columnar crystal growth, free from cracks and voids. With an increasing arc current, there was a notable increase in surface droplets, pits, and coating thickness. The coating deposited at a 140 A arc current showed a pronounced (200) orientation preference. The adhesion force peaked at 56.0 N with a subsequent decline, and the friction coefficient hit its lowest point of 0.429 at 140 A, contrasting with its highest value of 0.55 at 160 A. After 39 min of dry milling, the tool with a 140 A AlTiN coating exhibited minimal wear of 0.196 mm, just below the 0.2 mm failure threshold, indicating superior performance at this arc current setting. [ABSTRACT FROM AUTHOR]

Copyright of Lithuanian Journal of Physics is the property of Lithuanian Academy of Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Austenitic stainless steel has high toughness and plasticity; however, it tends to exhibit low yield strength, which severely limits the widespread application of this steel. It can be strengthened by cold working; however, this will cause many defects in the structure. Therefore, annealing treatment must be carried out before use. In this paper, the effects of annealing treatment at different temperatures and times on the microstructure and mechanical properties of cold-rolled 305 stainless steel sheet were studied and the theoretical mechanism was further analyzed to provide better theoretical guidance for production and application. It was found that the microstructure grains obtained by annealing at 850 °C for 30 s were finer and more uniform, and the mechanical properties were also the best, which met the requirements of strong plasticity. Therefore, the rolling and annealing experiments could be carried out again under this annealing condition, and the requirements of the finished product could be finally obtained. At this time, the thickness of the plate was about 0.15 mm, the yield strength was 1238 MPa, and the permeability was below 1.02, which met the production requirements of the metal mask plate. [ABSTRACT FROM AUTHOR]

Stainless steel (SS) exhibits excellent ductility; however, its low strength hinders its practical applications. To achieve good synergy between strength and ductility, a heterogeneous structure was introduced into a newly developed nitrogen-alloyed low-nickel austenitic steel, QN1803. The received QN1803 was cold-rolled and annealed at 993 K for different durations, and the microstructural evolution and tensile mechanical properties were investigated. The yield strength (1130 MPa) of the QN1803 annealed at a temperature of 993 K for 15 min was approximately three times higher than that of the as-received sample (314 MPa). The short annealing time of 15 min yielded a heterogeneous structure with grain size distributions ranging from nanoscale to micron-scale. The annealed QN1803 exhibited typical dislocation cells and dislocation walls caused by slipping after cold rolling. During annealing, a step-like lamellar structure is formed. The high yield strength was obtained from the large number of twins and hard ultrafine grains. The good ductility is due to the large number of dislocations generated in the soft grains and the GNDs around the heterogeneous interfaces. Additionally, the lamella structure of the material also contributes to improved ductility to a certain degree. The aim of this paper is to develop new materials with both high yield strength and excellent toughness based on more economical materials cost. [ABSTRACT FROM AUTHOR]

Al2O3-forming austenitic steel (AFA steel) is an important candidate material for advanced reactor core components due to its excellent corrosion resistance and high temperature strength. Al is a strong ferrite-forming element. Therefore, it is necessary to increase the Ni content to stabilize austenite. Ni is expensive and highly active, and so increasing the Ni content not only increases the costs but also damages the radiation resistance. Mn is a low-cost austenitic stable element. Its substitution for Ni will not only help to improve the irradiation resistance of austenitic steel, but also reduce the cost. In order to explore the feasibility of Mn-substituted Ni-stabilized austenite in AFA steel, this paper summarized the research progress of Mn-added AFA steels, whilst the research status of traditional Mn-added austenitic steels are also referred to and compared herein. The effect of the addition of Mn on the microstructure and properties of AFA steel was analyzed. The results show that Mn can promote the precipitation of the M23C6 phase and inhibit the precipitation of the B2-NiAl phase and secondary NbC phase. With the increase in Mn content, the strength of AFA steel at room temperature and high temperature decreased slightly, the room temperature elongation increased slightly, while the high temperature elongation and creep resistance decreased obviously. In addition, for austenitic steel free of Al, the addition of Mn will destroy the oxide layer of Cr2O3, which will decrease the oxidation resistance of the steel. But the preliminary study shows that Mn has little effect on the Al2O3 oxide layer. It is worth studying the effect of Mn-substituted Ni on the oxidation resistance of AFA steel. In summary, more efforts are necessary to investigate the optimal Mn content to balance the advantages and disadvantages of introducing Mn instead of Ni. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to investigate the microstructure of laser-melted surface layers of austenitic steel for biomedical applications. The surface of prismatic specimens from AISI 321 stainless steel was treated by continuous CO2 laser. Three modes of laser processing were used, ensuring surface melting. The microstructure was observed by OM and SEM, while the chemical composition was investigated by EDX analysis. It was found that the microstructure of as-delivered steel was two-phase and relatively inhomogeneous in morphology and chemical composition. It consisted of austenite with grain sizes between 20 - 150 µm, relatively large amount of striped δ-ferrite and spherical carbides along the grain boundaries. After laser melting, the microstructure remained two-phase (δ-ferrite and austenite), but became more homogeneous in morphology and composition. Different dendrites morphology in the particular regions of the molten layer was confirmed - fine equiaxed dendrites on the top surface and columnar at the bottom of the molten pool. Delta-ferrite is located in the interdendritic areas and in larger amounts in the transition zone between the molten layer and the base metal. [ABSTRACT FROM AUTHOR]

In this paper, a "multi-thin foil" structure + "two-stage" reaction strategy was employed to prepare B2-FeAl based MIL composite, and the effects of two different processes: conventional low-temperature hot-press sintering (CLT-HP) and fast high-temperature hot-press sintering (FHT-HP) on microstructure and mechanical properties were investigated. The results show that the MIL composites prepared by the two processes both exhibit multi-layer structure consisting of residual stainless steel layer, newly formed intermetallic layer, and intermediate transition layer. The metal layer is composed of both α-Fe and γ-Fe phases for CLT-HP, but only γ-Fe phase for FHT-HP counterpart. The intermetallic layer and transition layer mainly contain B2-FeAl phase for the two processes. Interestingly, multiple-sublayer structure was formed in the intermetallic layer and its thickness is obviously smaller and uniform for CLT-HP than FHT-HP. A kinetics calculation based on one-dimension diffusion equation was conducted to model the growth of B2-FeAl intermetallic layer, which exhibits a good consistency with the experimental results in terms of reaction rate and concentration profiles. CLT-HP MIL composites have better comprehensive mechanical properties than FHT-HP counterpart, especially for the compressive strength in the direction parallel to the layers, which is approximately 1 GPa higher for the former than the latter. This is mainly attributed to a good transitional role in properties through the transition layer and multiple-crack fracture mechanism in the intermetallic layer for CLT-HP MIL composite. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) are newly developed materials that have many excellent properties, such as a high strength-to-weight ratio and excellent tensile properties. If high-entropy alloys and stainless steel are joined by welding, the advantages of their properties can be balanced. In this paper, dissimilar lap joining of Al 0.3 CoCrFeNi-HEA with 304 stainless steel was achieved using gas tungsten arc welding (GTAW) with different heat inputs. Macroscopic morphology, microstructure analysis and mechanical property tests of the welded joints were carried out. The results showed that the macroscopic morphology of the dissimilar welded joints is well-formed under different heat inputs. The penetration and width of the weld seam increased with the heat input, and the lap area of the welded joint also increased. There was the same microstructure in the weld seam with different heat inputs, including columnar dendrites near the fusion line and equiaxed dendrites at the weld centre. The ultimate shear strength of the welded joints increased from 442 MPa to 560 MPa with increasing heat input, and the elongation of the welded joints increased from 26 % to 41 %. With increasing heat input, the average microhardness of the weld zone (WZ) was approximately 145 HV. [ABSTRACT FROM AUTHOR]

This paper employs OM, XRD, EBSD and mechanical properties testing to investigate the influence of shot peening on the microstructure and mechanical properties of 3D-printed 316L stainless steel. The following explores changes in the microstructure and mechanical properties of 316L stainless steel by 3D printing with different forming angles after shot peening: (1) As the forming angle increased from 0° to 90°, the microstructure of 3D-printed 316L stainless steel became significantly refined, and the thickness of ultrafine microstructure in the surface layer increased from 5 to 70 μm; (2) the hardness of the material increased from 471 HV to 482 HV as the forming angle increased from 0° to 90°; (3) According to the EBSD results, the enhanced hardness was attributed to refinement hardening and dislocation hardening. Moreover, the maximum yield strength (YS), ultimate tensile strength (UTS), and tensile elongation (TE) of 845, 862 MPa, and 17.8%, respectively, were obtained when the forming angle was 90°. [ABSTRACT FROM AUTHOR]

This paper presents new technology for stainless steel wire processing. This technology consists of using cryogenic cooling immediately after the wire leaves the drawing die. Results of a laboratory experiment show that use of cryogenic processing after wire drawing improves mechanical properties compared with traditional drawing. Metallographic analysis proves that deformation conditions during cryogenic drawing are an additional factor for realization of structural resources to optimize steel wire physical and mechanical properties. [ABSTRACT FROM AUTHOR]

Tribaloy™ T800, a Co-based alloy, exhibits remarkable tribological properties by virtue of its high-volume fraction of intermetallic Laves phase making it an attractive hard-facing material. Hard-facing by laser deposition results in dilution from the substrate, and thereby, the properties of the clad are altered. This paper reports the influence of processing parameters on the dilution, microstructure, and wear behaviour of Tribaloy™ T800 on AISI 316 stainless steel. A systematic set of 20 clads was deposited by varying laser power and cladding speed, keeping powder flow and spot diameter constant. While dilution decreased at lower laser powers (800 and 1000 W) with increasing cladding speed (5–20 mm s−1), at higher laser powers (1200 and 1400 W), the opposite trend was observed. The Fe intermixing from the substrate along with the cooling rate governs the volume fraction and size of the Laves phases which controls the properties of T800 clads. The clad with the least geometric dilution (5.7%) exhibits the lowest wear rate of 0.54 × 10−5 mm3 N−1 m−1, increasing to 2.88 × 10−5 mm3 N−1 m−1 as the dilution increased to 60%. [ABSTRACT FROM AUTHOR]

This paper features a direct comparison of the response of AISI 316L and AISI 304 austenitic stainless steels to active screen plasma nitrocarburizing applied for a wide range of treatment temperatures from 380 °C to 480 °C (653 K to 753 K). Thereby, an active screen made of solid carbon was used without applying bias plasma to the treated steel samples. Since it is believed that the result of treatment strongly depends on the concentration of in-situ generated hydrogen cyanide, the conditions of the treatments were adapted to keep this concentration constant. Under such treatment conditions, it was shown that AISI 316L has a lower tendency to form CrN than AISI 304 at comparable treatment temperatures, where the threshold temperature was found below 480 °C (753 K) for the former and below 440 °C (713 K) for the latter. In addition, the decomposition of expanded austenite generated on the treated AISI 316L at high temperatures leads to CrN and (mainly) Cr-depleted austenite phase, which is possibly accompanied by minor amounts of α -ferrite. Instead, for the treated AISI 304, decomposition leads to CrN and transformed α -ferrite phase. The modified layer thicknesses achieved after a given treatment duration and the kinetics of the layer growth showed a characteristic temperature dependence for each steel, which is discussed in accordance with the results of microstructure analysis. [ABSTRACT FROM AUTHOR]

This paper reports the microstructure and corrosion behavior of a Nb-containing stainless steel surfacing layer prepared by tungsten inert gas (TIG) powder surfacing. The focus was to achieve a clear understanding of the relationships between the Nb-addition and cavitation erosion behavior. In order to eliminate the microstructure inhomogeneity of as-welded samples, solution heat treatment was carried out. It is considered to set the heat treatment temperature at 1150 °C and 1250 °C to minimize the precipitation phase. Results showed that due to the Nb addition the as-welded 22Cr9Ni3MoNb surfacing layer had higher hardness, a lower pitting potential, and better cavitation erosion resistance. Because of the existence of a great quantity of precipitates, heat treatment at 1250 °C had an adverse effect on the mechanical properties and cavitation erosion resistance of surfacing layer samples. [ABSTRACT FROM AUTHOR]

This paper investigated the microstructure and mechanical properties of AISI 430 ferritic stainless steel (FSS) after annealing in either the single-phase or two-phase region, followed by different cooling manners: water cooling, air cooling and furnace cooling. After annealing at 840 °C in the single-phase region, the sample consisted primarily of ferrite, with M 23 C 6 and M 2 (C, N) precipitates aligned mainly along the rolling direction (RD). For the water-cooled and air-cooled samples annealed at 950 °C in the double-phase region, they formed a dual-phase structure comprising ferrite and martensite, with precipitations primarily located within the martensite lath. Conversely, the sample subjected to annealing at 950 °C followed by furnace cooling displayed a single ferrite structure, owing to the decomposition of austenite. In this case, the precipitations were mainly found along the grain boundaries, with some also forming within the ferrite grain. The paper delved into the analysis of mechanical properties and strengthening mechanism through tensile experiments and fracture morphology examination. The influence of heating range and cooling manner on the yield characteristics of FSS was discussed. The results indicated that the air-cooled and furnace-cooled samples annealed at 840 °C displayed a clear yield platform in their tensile curves. Conversely, the samples treated with other heat treatments exhibited continuous yielding or no obvious yield platform. This difference may be attributed to the influence of heating temperature range and cooling manner on the distribution of dislocations and interstitial atoms within the ferrite grains. [ABSTRACT FROM AUTHOR]

• The Cantor and BJAM 316L alloys show comparable dynamic shear response. • The Cantor and BJAM 316L alloys fail by intensive localized shear failure. • The sharpness affects adiabatic shear resistance of the Cantor and BJAM 316L alloys. • The failure parameters decrease linearly with the increase of inverse root radius. This paper examines the adiabatic shear resistance of recently popular Cantor alloy and Binder Jetting Additive Manufacturing (BJAM) 316L, with emphasis on their dependence on geometrical imperfection. A series of shear tests were conducted by using the long Split Hopkinson bar and shear compression specimen (SCS). Both alloys present strain rate dependent shear behaviour with the large dynamic shear failure strain of about 104 %–132 %. Microstructural characterizations reveal that both Cantor and BJAM 316L alloys fail by adiabatic shear band. Introduced by the varying notch root radius, the sharpness significantly affects the dynamic shear resistance of the Cantor and BJAM 316L alloys. The linear functions are proposed to describe the drop of critical strain and energy density with the designed inverse root radius. [ABSTRACT FROM AUTHOR]

Repair offers significant time—cost savings and durability by reusing existing parts efficiently. Prior to implementation of repaired parts, it is crucial to clarify mechanical properties and deformation mechanisms to ensure proper performance. In this study, a repair deposition was performed on the groove of wrought stainless steel 316L using the same material powder. The repaired sample exhibited an excellent combination of ductility and strength (T.EL: 58%, YS: 407 MPa, UTS: 673 MPa) compared to the wrought counterpart. With heterogeneity in microstructure, the hetero-deformation-induced strengthening of the repaired sample resulted in a synergy of strength-ductility combinations. [ABSTRACT FROM AUTHOR]

This study investigated the fatigue performance of 316L stainless steel fabricated via laser powder bed fusion (LPBF). Stress-controlled fatigue tests were performed at different stress amplitudes on vertically built samples using a frequency of 15 Hz and a stress ratio of 0.1. The stress amplitudes were varied to provide the cyclic response of the materials under a range of loading conditions. The average fatigue strength was determined to be 92.94 MPa, corresponding to a maximum stress of 185.87 MPa. The microstructures were observed through scanning electron microscopy (SEM) with the aid of electron backscattered diffraction (EBSD), and the average grain size of the as-built samples was determined to be 15.6 µm, with most grains having a <110> preferred crystallographic orientation. A higher kernel average misorientation value was measured on the deformed surfaces, revealing the increased misorientation of the grains. Defects were observed on the fractured surfaces acting as crack initiators while deflecting the crack propagation paths. The fatigue failure mode for the LPBF 316L samples was ductile, as illustrated by the numerous dimples on fracture surfaces and fatigue striations. [ABSTRACT FROM AUTHOR]

In this study, to improve the fatigue strength of the LDED (laser-directed energy deposition) 316L stainless steel, an in situ ultrasonic rolling technology is developed to assist the laser-directed energy deposition process (LDED-UR). The microstructural characteristics and fatigue behavior are comprehensively discussed. The results show that the average size of pores of the LDED-UR alloy is about 10.2 μm, which is much smaller than that of the LDED alloy (34.1 μm). Meanwhile, the density of the LDED alloy is also enhanced from 98.26% to 99.27% via the in situ ultrasonic rolling. With the application of the in situ ultrasonic rolling, the grains are transformed into fully equiaxed grains, and their average grain size is greatly reduced from 84.56 μm to 26.93 μm. The fatigue limit of the LDED-UR alloy is increased by 29% from 210 MPa (LDED alloy) to 270 MPa, which can be ascribed to the decreased porosity and the fine grains. In particular, the crack initiation site of the LDED alloy is located at the surfaces, while it is nucleated from the sub-surface for the LDED-UR alloy. This is mainly attributed to the compression residual stress induced by the in situ ultrasonic rolling. This research offers a valuable understanding of the failure mechanisms in additively manufactured metals, guiding the development of effective strategies to improve their fatigue threshold under severe operating conditions. [ABSTRACT FROM AUTHOR]

The effects of overlap rate and defects on the corrosion resistance of laser fusion clad austenitic stainless steel coatings were studied. In this paper, the Ni transition layer and Fe-based coating were sequentially prepared on grey cast iron, and the corrosion morphology and corrosion mechanism of the coating were comprehensively analyzed through physical phase, microstructure and electrochemical tests. The coating phase was mainly γ-Fe, which formed strong selective orientation and texture strength at the (100) crystal plane; overlap ratio and defects affected the recrystallization changes, and the stresses near the defects were high. Increased overlap rate (Fe-based alloy 50 % → 66.7 %) could result in microstructure refinement, reduced corrosion rate v (A8 6.22×10−4 g/m2·h→A9 3.12×10−5 g/m2·h), and improved corrosion resistance. Corrosion cracking extended the crack and embrittled the alloy at the tips of the cracks, so that its (|Z| max 0.67 ∼ 1.31×104 Ω cm2) influence on the corrosion resistance was much higher than that of the pore (|Z| max 5.85 ∼ 10.2×104 Ω cm2). The best corrosion resistance of the process was achieved with an overlap ratio of 66.7 % for both the Ni transition layer and the Fe-based coating. • Different laser overlap cladding manufactured transition layer – Fe-based coating. • Defect characteristics and change mechanisms were analyzed. • Overlap rate and defects on corrosion resistance of coating mechanism were analyzed. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the microstructure and mechanical properties of S31603 + Q355B stainless-clad (SC) bimetallic steel welded connections with different welding configurations. A comprehensive research approach was employed, including microstructure analysis, static tensile test, impact test, bending test, Vickers hardness distribution measurement, and analysis of welding economy and efficiency. Four types of welded connections were examined to understand their performance variations arising from different welding configurations. Based on the findings, a recommended welding configuration suitable for structural engineering applications was proposed. Research outcomes showed that the decarburization and carbon accumulation zones were observed at the fusion interface during the welding of dissimilar metals. It should be noted that martensite was formed in the substrate, or the base metal, due to diffusion of alloying elements, with a more pronounced effect observed with higher welding heat inputs. In order to minimize the fusion area of dissimilar metals, it is advisable to avoid using a single welding consumable made of stainless steel as the mechanical properties of the welded connection were not significantly influenced by the use of stainless steel welding consumables with higher Nickle (Ni) and Chromium (Cr) alloying content in the transition region. Consequently, the same welding consumable should be employed in the transition region to simplify the welding procedure and to enhance the welding efficiency. • Micro-macro tests on stainless-clad bimetallic steel welded connections were done. • Effects of various welding configurations were clarified. • The unique behaviour of transition weld zones were described. • The advantages and disadvantages of each welding configuration were discussed. • The recommended welding configuration was proposed. [ABSTRACT FROM AUTHOR]

Duplex Stainless Steels (DSSs) have excellent mechanical properties and corrosion resistance thanks to the biphasic ferritic-austenitic microstructure. This microstructure feature is highly influenced by the welding heat cycles. In this research paper, the effect of gas tungsten arc welding (GTAW) and submerged-arc welding (SAW) on the microstructure, mechanical and corrosion properties of SAF 2507 duplex stainless steel (DSS) were investigated. The base metal had the austenite content of 45 %, while the weld metals show variation of austenite contents in different regions. The middle regions of the both welds (GTAW ∼ 60.5 %, SAW ∼ 49.3 %) showed higher austenite contents than that of the root (GTAW ∼ 25.6 %, SAW ∼ 40.9 %) and top (GTAW ∼ 44.2 %, SAW ∼ 34.2 %) regions. Subsequent heat cycles promoted the precipitation of austenite from the primary ferrite, resulting in the higher contents of austenite in the middle welds. The nanoindentation tests revealed the individual properties of the typical phases, i.e., γ-Fe ∼ 5.4 GPa and α-Fe ∼ 4.7 GPa in both weld metals. The average tensile strength of GTAW and SAW welded joints are 997 MPa and 1109 MPa, respectively. The corrosion behavior of the weld metal was also evaluated through potentiodynamic polarization curves. The as-welded joints exhibit slight decrease in corrosion resistance, as compared to the base metal. These two weld metals showed slightly difference in mechanical and corrosion resistance properties. SAW method is most recommended when large thickness or high efficiency welding is required. • Structure, mechanical properties and corrosion resistance of 2507 DSS were investigated. • The content of austenite phase was highly influenced by the welding heat cycles. • SAW was most recommended when large thickness or high efficiency welding is required. [ABSTRACT FROM AUTHOR]

• SLM-fabricated 430 FSS exhibits significant anisotropy. • SLM-fabricated 430 FSS contains second-phase oxides and high dislocations. • SLM-fabricated 430 FSS exhibits excellent strength with limited plasticity. • SLM-fabricated 430 FSS shows cleavage fractures. This study investigates the microstructure and mechanical properties of 430 ferritic stainless steel (FSS) fabricated via the selective laser melting (SLM) process. The mechanical properties and fracture morphologies of SLM-fabricated 430 FSS and conventional 430 FSS were compared in this paper. It was found that 430 FSS produced by SLM exhibits significant microstructural anisotropy, with higher dislocation density and the presence of oxides of silicon, manganese and aluminum. Regarding mechanical properties, 430 FSS fabricated via SLM process displays higher tensile strength and yield strength, as well as superior product of strength and elongation (PSE) and yield ratio, compared to those produced by conventional methods. Fracture morphology analysis revealed that SLM-fabricated 430 FSS primarily exhibited characteristics of cleavage fractures, whereas conventional 430 FSS showed typical features of ductile fractures. [ABSTRACT FROM AUTHOR]

• The densification behavior in different hatch distances was investigated. • The microstructure evolution was characterized and analyzed. • The strengthening mechanism was explored. • The relationship between microstructure and mechanical properties was established. Laser powder bed fusion (LPBF) of duplex stainless steel is a promising route to fabricate intricate parts with excellent mechanical properties. However, further understanding of build mechanisms is required to improve the process. This paper aims to better understand the influence of hatch distance on the densification behavior and figure out the correlation with microstructure and mechanical properties in LPBF of 2205 stainless steel. With the optimized laser power and scanning speed, the significant influence of hatch distance on the build quality is revealed. A hatch distance of 0.07 mm is selected for an even surface and dense part with a relative density of up to 99.13 %. The hatch distance has a crucial impact on the heat and mass transfer between tracks; hence, poor surface morphologies such as inter-track voids or swelling surfaces occur if an improper hatch distance is adopted. The optimal mechanical properties are also achieved. Specifically, the yield strength (0.2 YS), ultimate tensile strength (UTS), and elongation (EL) values are 896.8 MPa, 1035.13 MPa, and 15.34 %, respectively. The improvement in mechanical properties can be ascribed to the coordination between high dislocation density, fine grain size, high CSL boundaries and LAGBs, and high relative density with few pores. This work can help improve the build quality and expand the application horizon of duplex stainless steel for manufacturing intricate components. [ABSTRACT FROM AUTHOR]

Unlike polymers, glass is prone to fracturing under localized stress during roll embossing. Molds traditionally used for glass embossing are rigid and unsuitable for roll embossing. In this investigation, we utilized a modified soft polydimethylsiloxane (PDMS) mold, known for its ease of fabrication and superior replication capacity, for roller embossing on glass. This innovation significantly cuts mold expenses while preserving PDMS's hydrophobic and low surface energy attributes. Consequently, it prevents adhesion between the glass and the mold during high-temperature embossing, ensuring that the demolding process does not harm the glass surface. We successfully carried out roll embossing on optical glass with a mere 1.65 mm thickness, using a self-devised stainless steel carrier plate and a mobile induction heating apparatus. This heating methodology departs from the conventional practice of employing multiple heat sources in glass embossing and instead uses a singular heat source. Induction heating is applied directly to the mold and 420 stainless steel carrier. The optical glass surface reaches a remarkably uniform temperature, with a minimal temperature differential of only 2.5 °C, which is highly advantageous for mobile roller embossing, resulting in a high replication rate of V-groove microstructures on glass. [ABSTRACT FROM AUTHOR]

Using finite element simulation and single-variable experimental methods, this study analyzes the variations in the microstructure and hardness of a 304 stainless steel wire during Joule heating fused filament fabrication. The effects of current intensity, printing speed, and roller pressure on the macroscopic morphology, microstructure, and microhardness of a single-layer single-channel formation were investigated. The results indicate that when the current intensity is 400 A, the printing speed is 1000 mm/min, and the roller pressure is 0.3 N, the surface of the single-layer single-channel formation is smooth and exhibits optimal forming characteristics with a width-to-height ratio of 3.23, a dilution rate of 51.61%, and an average microhardness of 238.17 HV. As the current intensity increases, the microstructure in the fusion zone initially decreases in size and then increases; similarly, with the increase in printing speed, the microstructure in the fusion zone first decreases and then increases; as the roller pressure increases, the microstructure in the fusion zone initially increases in size and then decreases. The microhardness initially increases and then decreases with the increase in process parameters, resulting in uneven hardness distribution due to the variations in microstructure size. The optimal combination of process parameters achieves a balance between heat input, cooling rate, and growth rate, thereby achieving grain refinement and hardness improvement, ultimately enhancing the mechanical properties of the material. [ABSTRACT FROM AUTHOR]

Stainless steel grade 430 is a type of soft magnetic electromagnetic material with rapid magnetization and demagnetization properties. Considering the delay phenomenon during operation, this study selected 430 stainless steel as the material and explored various metallurgical methods such as magnetic annealing and the addition of Mo as well as increasing the Si content to investigate the microstructure, mechanical behavior, and magnetic properties of each material, aiming to improve the magnetic properties of 430 stainless steel. Experimental results showed that the four electromagnetic steel materials (430F, 430F-MA, 434, and KM31) had equiaxed grain matrix structures, and excellent tensile and elongation properties were observed for each specimen. Additionally, the magnetic properties of the 430F specimen were similar under the DC and AC-10 Hz conditions. According to the hysteresis curves under different AC frequencies (10, 100, 1000 Hz), both magnetic annealing and the addition of Mo could reduce the Bm, Br, and Hc values of the raw 430F material. Increasing the Si content resulted in a decrease in Hc values and an increase in Bm and Br values. [ABSTRACT FROM AUTHOR]

In the present work, the evolution of the microstructure in additively manufactured 17-4PH stainless steel, which was subjected to laser surface alloying with amorphous boron and nitrogen at the varying process parameters, was studied. The main aim was to improve surface hardness and hence potential wear resistance of the steel. Scanning electron microscopy, wavelength-dispersive X-ray spectroscopy (WDS), and Auger electron spectroscopy (AES) were used. It was shown that the final microstructure developed in the laser-melted zone (LMZ) is dependent on a variety of processing parameters (1 and 1.5 mm laser beam spot diameters; 200, 400, and 600 mm/min laser scan speeds), which primarily influence the morphology and orientation of the eutectic dendrites in the LMZ. It was metallographically proven that a fully eutectic microstructure, except for one sample containing 60 ± 4.2% of the eutectic, was revealed in the LMZ in the studied samples. The results of WDS and AES also confirmed alloying the LMZ with nitrogen. The formation of the boron eutectic and the supersaturation of the α-iron solid solution with boron and nitrogen (as a part of the eutectic mixture) led to enhanced microhardness, which was significantly higher compared with that of the heat-treated substrate (545.8 ± 12.59–804.7 ± 19.4 vs. 276.8 ± 10.1–312.7 ± 11.7 HV0.1). [ABSTRACT FROM AUTHOR]

Austenitic stainless steels used in structural applications suffer from stress corrosion cracking due to residual stresses during welding. Much research is being conducted to prevent the stress corrosion cracking of austenitic steels by inducing compressive residual stresses. One method is ultrasonic shot peening (USP), which is used to apply compressive stress by modifying the mechanical properties of the material's surface. In this study, 304L stainless steel was butt-welded by gas tungsten arc welding (GTAW) and subsequently subjected to compressive residual stress to a depth of 1 mm from the surface by a USP treatment. The influence of USP on microstructural changes in the base metal, the HAZ and weldment, and the corrosion properties was analyzed. A microstructural analysis was conducted using SEM-EDS, XRD, and EBSD methods alongside residual stress measurements. The surface and cross-sectional corrosion behavior was evaluated and analyzed using a potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS) measurements, a double-loop electrochemical potentiokinetic reactivation (DL-EPR) test, and an ASTM A262 Pr. C test. The surface was deformed and roughened by the USP. The deformed areas formed crevices, and the inside of the crevices contained some cracks. The crevices and internal cracks caused pitting, which reduced the resistance of the passivation film. The cross-section was subjected to compressive residual stress to a depth of 1 mm from the surface, and the outermost area of the cross-section had fine grain refinement, forming a solid passivation film that improved the corrosion resistance. [ABSTRACT FROM AUTHOR]

This study aimed to develop an artificial neural network (ANN) model for predicting the yield strength of a weld metal composed of austenitic stainless steel and compare its performance with that of conventional multiple regression and machine learning models. The input parameters included the chemical composition of the nine effective elements (C, Si, Mn, P, S, Ni, Cr, Mo, and Cu) and the heat input per unit length. The ANN model (comprising five nodes in one hidden layer), which was constructed and trained using 60 data points, yielded an R2 value of 0.94 and a mean average percent error (MAPE) of 2.29%. During model verification, the ANN model exhibited superior prediction performance compared with the multiple regression and machine learning models, achieving an R2 value of 0.8644 and a MAPE of 3.06%. Consequently, the ANN model effectively predicted the variation in the yield strength and microstructure resulting from the thermal history and dilution during the welding of 3.5–9% Ni steels with stainless steel-based welding consumables. Furthermore, the application of the prediction model was demonstrated in the design of welding consumables and heat input for 9% Ni steel. [ABSTRACT FROM AUTHOR]

In this study, we investigated the micromechanical deformation and damage behavior of commercially extruded and additively manufactured 316L stainless steels (AMed SS316L) by combining experimental examinations and crystal plasticity modeling. The AMed alloy was fabricated using the laser powder bed fusion (LPBF) technique with an orthogonal scanning strategy to control the directionality of the as-fabricated material. Optical microscopy and electron backscatter diffraction measurements revealed distinct grain morphologies and crystallographic textures in the two alloys. Uniaxial tensile test results suggested that the LPBFed alloy exhibited an increased yield strength, reduced elongation, and comparable ultimate tensile strength in comparison to those of the extruded alloy. A microstructure-based crystal plasticity model was developed to simulate the micromechanical deformation behavior of the alloys using representative volume elements based on realistic microstructures. A ductile fracture criterion based on the microscopically dissipated plastic energy on a slip system was adopted to predict the microscopic damage accumulation of the alloys during plastic deformation. The developed model could accurately predict the stress–strain behavior and evolution of the crystallographic textures in both the alloys. We reveal that the increased yield strength in the LPBFed alloy, compared to that in the extruded alloy, is attributed to the higher as-manufactured dislocation density and the cellular subgrain structure, resulting in a reduced elongation. The presence of annealing twins and favorable texture in the extruded alloy contributed to its excellent elongation, along with a higher hardening rate owing to twin–dislocation interactions during plastic deformation. Moreover, the grain morphology and defect state (e.g., dislocations and twins) in the initial state can significantly affect strain localization and damage accumulation in alloys. [ABSTRACT FROM AUTHOR]

Stainless steels are used in a wide range of complex environments due to their excellent corrosion resistance. Multiphase stainless steels can offer an excellent combination of strength, toughness and corrosion resistance due to the coexistence of different microstructures. The microstructure and mechanical properties of a novel cast multiphase stainless steel, composed of martensite, ferrite, and austenite, were investigated following appropriate heat treatment processes: solution treatment at 1,050 °C for 0.5 h followed by water quenching to room temperature, and aging treatment at 500 °C for 4 h followed by water quenching to room temperature. Results show reversed austenite is formed by diffusion of Ni element during aging process, and the enrichment of Ni atoms directly determines the mechanical stability of austenite. The austenite with a lower Ni content undergoes a martensitic transformation during plastic deformation. The tensile strength of the specimen exceeds 1,100 MPa and the elongation exceeds 24% after solid solution, and further increases to 1,247 MPa and 25% after aging treatment. This enhancement is due to the TRIP effect of austenite and the precipitation of the nanoscale G-phase pinning dislocations in ferrite and martensite. [ABSTRACT FROM AUTHOR]

The dimensional accuracy and microstructure affect the service performance of parts fabricated by wire arc additive manufacturing (WAAM). Regulating the geometry and microstructure of such parts presents a challenge. The coupling method of an artificial neural network and finite element (FE) is proposed in this research for this purpose. Back-propagating neural networks (BPNN) based on optimization algorithms were established to predict the bead width (BW) and height (BH) of the deposited layers. Then, the bead geometry was modeled based on the predicted dimension, and 3D FE heat transfer simulation was performed to investigate the evolution of temperature and microstructure. The results showed that the errors in BW and BH were less than 6%, and the beetle antenna search BPNN model had the highest prediction accuracy compared to the other models. The simulated melt pool error was less than 5% with the experimental results. The decrease in the ratio of the temperature gradient and solidification rate induced the transition of solidified grains from cellular crystals to columnar dendrites and then to equiaxed dendrites. Accelerating the cooling rate increased the primary dendrite arm spacing and δ-ferrite content. These results indicate that the coupling model provides a pathway for regulating the dimensions and microstructures of manufactured parts. [ABSTRACT FROM AUTHOR]

Duplex stainless steels are materials with high performance under mechanical stress and stress corrosion in chloride ion environments. Despite being used in many new applications such as components for offshore drilling platforms as well as in the chemical and petrochemical industry, the automotive industry, etc., they face issues of wear and hardness that limit current applications and prevent the creation of new use opportunities. To address these shortcomings, it is proposed to develop a hardfacing process by a special welding technique using a universal TIG source adapted for manual welding with a pulsed current, and a manganese austenitic alloy electrode as filler material. The opportunity to deposit layers of manganese austenitic steel through welding creates advantages related to the possibility of achieving high mechanical characteristics of this steel exclusively in the working area of the part, while the substrate material will not undergo significant changes in chemical composition. As a result of the high strain hardening rate, assisted mainly by mechanical twinning, manganese austenitic alloys having a face-centered cubic crystal lattice (f.c.c) and low stacking fault energy (SFE = 20–40 mJ/m2) at room temperature, exhibit high wear resistance and exceptional toughness. Following cold deformation, the hardness of the deposited metal increases to 465 HV5–490 HV5. The microstructural characteristics were investigated through optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and Vickers hardness measurements (HV). The obtained results highlighted the feasibility of forming hard coatings on duplex stainless steel substrates. [ABSTRACT FROM AUTHOR]

Duplex stainless steels are widely used in many fields due to their excellent corrosion resistance and mechanical properties. However, it is a challenge to achieve duplex microstructure and excellent properties through additive manufacturing. In this work, a 0.09% N 25Cr-type duplex stainless steel was prepared by additive manufacturing (AM) and heat treatment, and its corrosion resistance was investigated. The results show that, compared with S32750 duplex stainless steel prepared by a conventional process, the combination value of film resistance and charge transfer resistance of AM duplex stainless steel was increased by 3.2–5.5 times and the pitting potential was increased by more than 100 mV. The disappearance of residual thermal stress and the reasonable distribution of Cr and N elements in the two phases are the reasons for the improvement of the corrosion resistance of AM duplex stainless steel after heat treatment. In addition, the extremely high purity of AM duplex stainless steel with no visible inclusions resulted in a higher corrosion resistance exhibited at lower pitting-resistance-equivalent number values. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The paper presents the 3-D model of the hydrogen diffusion in austenitic stainless steel. In order to model the material behaviour, a real microstructure taking into account the grain boundaries, the dislocations density, the vacancies number and the precipitates state was analysed in order to the implemented in the employed software (ANSYS). The effect of each single hydrogen trap was physically determined. The simulations were carried out by modelling the material microstructure with a high number of elements and nodes in order to improve the affordability of the obtained results. The model allowed to identify the hydrogen diffusion mode in different conditions by evaluating the weight that each single trap has on the overall process. The developed model allowed also to define the hydrogen saturation of the microstructure in different conditions of temperature. • Microstructural features act as different traps for hydrogen atoms in stainless steel. • Hydrogen saturation is very fast in grain boundary and dislocations. • Diffusion modelling is strongly related to the precise definition of the microstructure of the steel. • Hydrogen saturation is very pronounced as the temperature increases. [ABSTRACT FROM AUTHOR]