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Weld overlaying is a promising and economical solution for repairing stainless steel structures. The present work deals with the deposition of ER-308L weld overlays on AISI 321 plate with Robotic gas metal arc welding setup. Microstructural examination depicts the presence of dendritic structures (equiaxed and columnar) and ferritic stringers. Energy-dispersive X-ray analysis confirmed the absence of precipitates and phases susceptible to corrosion in the as-deposited weld overlays. Specimens from ER-308L (weld overlay) and ER-308L&321-SS (interface) regions were subjected to electrochemical analysis using the Potentiodynamic polarization and double-loop electrochemical potentiokinetic reactivation measurements. Both overlay and interface sections exhibited comparable corrosion rate – 3.30 and 3.62 mils penetration per year, respectively with different passivation behaviour. The improved passivation behaviour of the ER-308L weld overlay authenticates the presence of δ-ferrite stringers. Double-loop electrochemical potentiokinetic reactivation tests highlighted the absence of sensitization on both weld overlay and interface specimens. This study presents the initial assessment results for repairing structural steel components subjected to corrosion damage. [ABSTRACT FROM AUTHOR]

Additive Manufacturing techniques represent a revolution for the design of certain engineering components traditionally subject to a design highly influenced by the manufacturing process linked to the manufacture of the component. Additive Manufacturing techniques therefore allow components with different internal and external structures to be manufactured. Thus, components formed by an internal microstructure are of special interest due to their high strength-to-weight and high stiffness-to-weight properties. This work investigates the hybrid fabrication of curved thin-walled Inconel 718 with internal microstructural supports fabricated by laser powder bed fusion (LPBF). The outer walls are made up of solid surfaces with a fixed curvature and thickness, while the internal structure of the pieces is made up of internal microstructures that vary at different angles of inclination. Finally, the outer surfaces of the piece have been milled. Eventually, the dimensional quality of the components and their internal microstructure has been analysed. [ABSTRACT FROM AUTHOR]

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The evolution of the microstructure and texture of a newly developed Mg alloy Mg-6.9Sn-2.6Zn (TZ73) and its effect on tensile behaviour has been studied as a function of strain path change during hot rolling. The two strain paths employed are cross-rolling plus unidirectional rolling (CR-UDR) and reverse rolling (RR). The RR process led to a slightly higher fraction of dynamically recrystallized grains, slightly finer grain size, more uniform distribution of fine Mg2Sn particles, and weaker texture than the CR-UDR process. The RR processed sheet exhibited higher tensile strength and ductility in all the directions and less anisotropy in tensile properties than the CR-UDR processed sheet. The RR processed TZ73 alloy exhibited higher strength and ductility in the rolling direction than the other commercial and experimental rare earth-free hot-rolled Mg alloys reported in the literature. [ABSTRACT FROM AUTHOR]

Lactobacillus rhamnosus GG (LGG) is an acceptable probiotic strain that can live and grow at a gastrointestinal acidic pH and on a bile-rich medium. The influence of spraydrying microencapsulation of LGG on the physicochemical parameters and survivability was investigated in the present work. LGG was spray-dried with three different maltodextrin concentrations (6, 12, and 18% w/v). The inlet and outlet air temperatures of the spray-dryer were kept at 170 ± 5°C and 75 ± 5°C, respectively. The physicochemical parameters (moisture content (wet basis), water activity, and colour), viability (colony forming unit/g), and simulated gastrointestinal digestion were all investigated. Only 18% MD was selected on the basis of moisture content and log CFU/g. The total soluble solids (TSS) of 16.28 ± 0.93 °Brix were obtained using 18% MD. The end product had a moisture content of 5.40 ± 0.20%, and a water activity of 0.32 ± 0.02 aw, which were acceptable. The L*, a*, and b* of the final product were 95.14 ± 0.19, -2.33 ± 0.02, and 7.17 ± 0.13, respectively. The spray-dried powder had final probiotic viability of around 108 CFU/g. Based on the study, maltodextrin at 18% (w/v) concentration can be considered as an ideal formulation with acceptable powder characteristics for shielding probiotic microorganisms from harmful conditions of spray-drying. [ABSTRACT FROM AUTHOR]

In this study, fiber laser beam welding was used to join 3 mm-thick nitronic-50 stainless steel. The effect of travel speed on the mechanical, microstructural, and corrosion properties of the weld joints was studied. The experimental findings reveal that travel speed significantly affected the size of bead geometry and the fusion boundary of the weld joints. The microstructure of columnar grains transformed into equiaxed dendritic grains at the center of the weld nugget due to fast cooling at higher travel speeds. The increase in ferrite content was due to the incomplete transformation of ferrite to austenite at higher travel speeds, which led to higher strength and microhardness in the weld joints. Similarly, the corrosion studies demonstrate that the weld joints made at higher travel speeds have superior corrosion resistance due to a higher fraction of equiaxed dendritic grains and smaller dendrites with less inter-dendritic arm spacing. [ABSTRACT FROM AUTHOR]

Pure Copper having excellent electrical conductivity was deposited over AISI 347 substrate using Cold Metal Transfer (CMT) process to obtain quality weld overlays without defects. To improve the electrical conductivity post heat-treatment was performed. The microstructural examination revealed the presence of Cu-FCC and Fe-FCC along with retained delta ferrite at the bi-metallic interface. Also, the existence of bi-phasic spherulites rich in Fe and Cr were noticed in the weld overlay side while Cu spherulites were observed in the AISI 347 substrate adjacent to the bi-metallic interface. Energy Dispersive X-Ray Spectroscopy (EDS) elemental mapping and line scan data confirmed the presence of spherulites due to solid-state diffusion near the interface. The spherulite size was reduced in the heat-treated weld overlays and a small fraction of Cu spherulites were observed in the interface. The microhardness of the as-deposited and heat-treated weld overlays revealed the transition of elements at the bi-metallic interface. Post heat-treatment of Cu weld overlays improved the electrical conductivity significantly in comparison to the as-deposited ones. These electrical measurements suggest that pure Cu weld overlays with sufficient conductivity shall be attained with the CMT process for electrical and power generation applications. [ABSTRACT FROM AUTHOR]

In this paper, an attempt was made to study the ballistic resistance of Friction Stir Welded (FSW) AZ31B magnesium alloy. The base metal AZ31B plates were sliced to required size and FSW was carried out using a non-consumable taper pin tool made up of HCHCr steel. Samples were taken out from the FSW plates to study the microstructure and microhardness. The FSW AZ31B contain refined grains and tiny Mg17Al12 precipitates which were formed because of severe plastic deformation during FSW. The FSW AZ31B targets also showed ∼7.47% increase in microhardness compared to BM target. Further, ballistic test was conducted by impacting Ø7.62 × 39 mm hard steel core projectiles at an initial velocity of 420 m/s. AA6062 material of 25 mm was used as backing plate to measure the Depth of Penetration (DOP) of the projectile. The failure mechanism and the ballistic resistance of BM and FSW AZ31B samples were studied and compared. Finally, post ballistic analysis was made to study the failure modes of the target at microscopic level. Through various experimental results, it was identified that the increase in ballistic resistance of FSW AZ31B target was mainly due to two reasons; the refinement of grain size and small strengthening precipitates. [ABSTRACT FROM AUTHOR]

In the present study, functionally graded material (FGM) of Austenitic Stainless Steel-SS 316L and Nickel-based superalloy-Inconel 625 (IN625) was manufactured via Gas Metal Arc Welding (GMAW) based Wire Arc Additive Manufacturing (WAAM). WAAM processed FGM was well-formed without any defects and solidification cracking was not observed at the bi-metallic interface (IF) region. Microstructural features show a sharp transition at the IF with a discontinued dendritic structure. Energy-dispersive X-ray spectroscopy (EDS) examination confirmed the fine dissolution of elements at the IF and no major difference in the composition was observed. Electron Backscatter Diffraction (EBSD) maps confirmed that the grains are dominantly columnar while the IF revealed the smooth crystallographic growth along with large elongated dendrites in the< 001 >direction. The microstructure was mainly austenitic in the SS 316L layers with a lower fraction of ferrite while precipitates were noticed in the IN625 layers within the austenitic matrix. Yield strength (YS) and tensile strength (UTS) of SS 316L and IN625 were comparable with wrought ones. All the IF samples at 90° failed in the SS 316L region because of the lower UTS in comparison to IN625 and the mode of fracture was ductile. Microhardness measurements depicted the gradual change of hardness along the building direction. The present work highlights the potential of WAAM to fabricate FGM with required properties and is a viable manufacturing alternative to the traditional manufacturing techniques for producingFGM's. [Display omitted] [ABSTRACT FROM AUTHOR]

In the current work, ZE41 Mg alloy was processed by friction stir processing (FSP) to achieve grain refinement. In addition to grain refinement, decreased intermetallic phase (MgZn) was also observed after FSP. Increased micro-hardness was observed for the processed ZE41 Mg alloy compared to the unprocessed base alloy. X-ray diffraction (XRD) studies demonstrated the texture characteristics in FSPed ZE41. Reciprocating wear studies conducted at three different temperatures, i.e. room temperature, 125 °C, and 250 °C showed lower mass loss for the processed alloy compared to that of the base alloy, particularly at elevated temperatures. This behavior can be understood by considering the benefit gained from the smaller grains and decreased amount of intermetallic phase in the processed alloy, which reduced the abrasion wear. Hence, the present study suggests that the grain refinement and decreased MgZn phase significantly improve the temperature-dependent tribological characteristics of ZE41 Mg alloy. [ABSTRACT FROM AUTHOR]