SS316L Alloy Research Articles

Role of nitrogen on fatigue crack growth behaviour of low carbon nitrogen alloyed stainless steel at different load ratios and temperatures

Fatigue crack growth (FCG) behaviour of nitrogen added (0.078 wt%–0.22 wt%) SS316L alloy has been evaluated near threshold and Paris regimes at different load ratios and temperatures. The variations in the threshold (ΔKth) with nitrogen at room temperature and high temperature were found to follow the same trend at a low load ratio. However, the role of nitrogen on the threshold behaviour at high temperatures and a load ratio of 0.7 is insignificant. These variations have been examined in terms of microstructure, slip character, crack closure and dynamic strain ageing (DSA) effects. The improved ΔKth at high temperatures and different load ratios are due to the synergetic effect of the environment, crack tip strain rate and DSA rather than the crack closure. Based on the present study, it has been suggested that the nitrogen level in SS316L alloy should be more than 0.12 wt% when using material in high-temperature applications.

Finite element analysis and optimization studies on tibia implant of SS 316L steel and Ti6Al4V alloy

Tibial fractures account for approximately 15% of all fractures, typically resulting from high-energy trauma. A critical surgical approach to treat these fractures involves the fixation of the tibia using a plate with minimally invasive osteosynthesis. The selection and fixation of the implant plate are vital for stabilizing the fracture. This selection is highly dependent on the plate's stability, which is influenced by factors like the stresses generated in the plate due to the load on the bone, as well as the plate's length, thickness, and number of screw holes. Minimizing these stresses is essential to reduce the risk of implant failure, ensuring optimal stress distribution and promoting faster, more effective bone healing. In the present work, the finite element and statistical approach was used to optimize the geometrical parameters of the implant plate made of SS 316L steel and Ti6Al4V alloy. A 3D finite element model was developed for analyzing the stresses and deformation, and implant plates were manufactured to validate the results with the help of an experiment conducted on the universal testing machine. A strong correlation was observed between the experimental and predicted results, with an average error of 8.6% and 8.55% for SS316L and Ti6Al4V alloy, respectively. Further, using the signal-to-noise ratio for the minimum stress condition was applied to identify the optimum parameters of the plate. Finally, regression models were developed to predict the stresses generated in SS316L and Ti6Al4V alloy plates with different input conditions. The statistical model helps us to develop the relation between different geometrical parameters of the Tibia implant plate. As determined by the present work, the parameter most influencing is implant plate length. This outcome will be used to select the implant for a specific patient, resulting in a reduction in implant failure post-surgery.

Tribological behavior and surface characteristics of severe surface plastic deformed as-cast and 3D-printed SS316L using LSP

The effect of laser shock peening (LSP) on as-cast and three-dimensional (3D)-printed SS316L alloys was studied. The LSP process was found more dominant than the 3D-printing technique over as-cast alloy steel for enhancing the properties. The process of laser shock peening results in microlevel changes in the structure of the material. This, in turn, leads to grain refinement and the increase of compressive residual stresses. After LSP treatment, the surface microhardness value increased by 33% in both as-cast and 3D-printed SS316L alloys with the hardness gradient from surface to subsurfaces. The wear rate of as-cast specimens and 3D-printed specimens were reduced to 1.28 10−6 and 1.14 10−6 g/m, respectively, and tensile value increased up to 22% after LSP treatment. The scanning electron microscopy images on the wear track confirm the vulnerability of the untreated SS316L alloys with adhesion wear and surface delamination. This difference was because the wear rate of the 3D-printed specimens was lesser than the as-cast SS316L alloys due to their layer-by-layer high-temperature finishing. The samples were characterized by optical microstructure to identify the surface refinement, and confirmed by the transmission electron microscope images along with specified area electron diffraction pattern for the accumulation of dislocation and grain refinement after LSP treatment. The accumulated residual stress was measured by X-ray diffraction technique and it found the highest compressive residual stress after LSP treatment was accrued by 3D-printed SS316L alloy with 310 MPa.

Investigation and In Vitro Studies of a ZrO2/g‐C3N4 Composite Coated on 316L Stainless Steel for Biomedical Applications

ABSTRACTThe advancement of smart coatings for bioimplants has yielded a combination of biocompatibility and corrosion resistance. 316L stainless steel (316LSS) is a commonly used commercial implant, but it has limitations in biocompatibility and durability, which hinders the widespread utilization of 316LSS alloys. In this study, the 316LSS alloy is coated with a mixture of zirconium dioxide (ZrO2), prepared using the sol–gel method, and graphitic carbon nitride (g‐C3N4), synthesized by thermal polymerization. XRD and Raman analyses confirmed the crystal structure and purity of the synthesized samples. The corrosion resistance property was assessed using OCP, POL, and PEIS. The findings demonstrate that the ZrO2/g‐C3N4‐coated 316LSS shows significantly enhanced corrosion resistance and biocompatibility in a simulated body fluid. The in vitro bioactivity test reveals that the ZrO2/g‐C3N4 coating leads to the formation of an apatite layer over the surface of 316LSS. The elemental composition of the HAP deposition was confirmed by Raman analysis. The results suggested that the ZrO2/g‐C3N4–coated 316LSS substrate is a promising material for use in biomedical applications.

Triboinformatic Machine Learning Model for Frictional Behavior and Wear Volume Loss Prediction of SS316L Alloy Clad with WC/NiCrBSi

Triboinformatic Machine Learning Model for Frictional Behavior and Wear Volume Loss Prediction of SS316L Alloy Clad with WC/NiCrBSi

Surface Evaluation of Tricalcium Phosphate Bioceramic Coating on SS-316L by Electrophoretic Deposition

The development of orthopedic implant materials has become an important topic of discussion lately. The SS-316L alloy is widely used as an implant material due to its relatively low cost, corrosion resistance, and ease of production. However, metal alloys, especially SS-316L, are prone to ion release into the blood over time. Therefore, TCP or tricalcium phosphate [Ca3(PO4)2] is needed to coat the surface of SS-316L, preventing ion release into the blood and enhancing the biocompatibility of the implant material. In this study, TCP coating was applied to the SS-316L substrate using the electrophoretic deposition technique. The influence of deposition time on changes in microstructure and mechanical properties is the main focus of this study. The results of the coating technique indicate that the deposition yield increases with the deposition time. Morphological testing results show that increasing deposition time improves coating quality by increasing the thickness of the coating layer and preventing layer peeling. The coating process also reveals the accumulation of layers in certain areas and the formation of thin layers in other regions. A deposition time of 30 minutes results in a coating thickness ranging from 48.7 to 57.9 µm. Hardness testing, conducted with indentation loads of 50, 100, and 300 gf, indicates that longer deposition times and higher indentation loads during hardness testing result in reduced material hardness.

A comparison of clinical outcomes between narrow and broad dynamic compression plate for femur fractures

Purpose: To review the short term performance 4.5/5.0mm Wise-Lock Narrow Dynamic Compression Plate with LC under cuts and 4.5/5.0mm Wise-Lock Broad Dynamic Compression Plate with LC under cuts for femur fractures in terms of postoperative complications and failure rates. Methods: The total number of 46 patients, 24 to 55 years’ age group, who underwent internal fixation with wise-lock narrow and broad dynamic compression plate for femur fractures were reviewed. These implants were manufactured at Auxein Medical Private Limited Sonipat (India). The wise-lock narrow dynamic compression plates were implanted to 24 patients (18 Male and 05 Female) and broad dynamic compression plates were implanted to 22 patients (15 Male and 08 Female). These plates were made up of SS 316L and Ti6Al4V alloy respectively. Clinical and radiological follow-ups were conducted at the end of 30 days, 90 days, 180 days, 270 days and 365 days after surgery to examine the bone union, non-union & other related complications. During the one year of follow-up by the surgeon the patient's health status was analysed by the American society of anesthesiologists grade and the visual analogue score (VAS) was also determined. Results: Patients were followed up for one year. Out of 24 patients who were treated with wise-lock narrow dynamic compression plate, stainless steel, 04 patients (03 males & 01 female) were faced the complications of pain. However, out of 22 patients who were treated with broad dynamic compression plate, titanium, 02 patients (02 males) developed complications of pain. No biomechanical issue related to screw loosening, corrosion, bending, or other factors was not detected in 46 patients. Conclusions: Femur plate fixation is feasible for the treatment of femur fracture. The clinical outcomes and prognosis of patients are dependent on the accuracy of intraoperative reduction and surgical expertise.

Corrosion Behavior of Candidate Structural Materials for Molten Salt Reactors in Flowing NaCl-MgCl2

Abstracts. A high-temperature molten salt natural convection loop was designed and manufactured for chloride-based salts. NaCl-MgCl2 salt was prepared and injected into the loop. Corrosion coupons composed of SS304, SS316L, and high-Ni alloys were also prepared as candidate structural materials for molten chloride salt reactors. After a corrosion experiment was conducted for 500 h, the salt was drained from the loop to the drain tank; inductively coupled plasma optical emission spectroscopy was used to investigate metal dissolution from the materials into the salt. The corroded materials were analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy to calculate the corrosion rate. Materials exposed to NaCl-MgCl2 molten salt showed varying levels of corrosion resistance. The high-Ni alloy demonstrated the highest resistance, followed by SS316L and SS304. Furthermore, corrosion products were observed to migrate along the molten salt through natural convection, eventually depositing onto the surface of the high-Ni alloy in the cold leg of the loop.

Nanoscale and Tensile-Like Properties by an Instrumented Indentation Test on PBF-LB SS 316L Steel.

The mechanical properties of a defect-free laser melting (PBF-LB) deposit of an AISI 316L steel alloy were assessed by means of an instrumented indentation test (IIT), at both the macro- and nano-scales. The inherent non-equilibrium microstructure of the alloy was chemically homogenous and consisted of equiaxed grains and large-elongated grains (under the optical microscope) with irregular outlines composed of a much finer internal cell structure (under the scanning electron microscope). Berkovich and Vickers indenters were used to assess the indentation properties across individual grains (nano) and over multiple grains (macro), respectively. The nano-indentation over the X-Y plane revealed nearly constant indentation modulus across an individual grain but variable on average within different grains whose value depended on the relative orientation of the individual grain. The macro-indentation test was conducted to analyze the tensile-like properties of the polycrystalline SS 316L alloy over the X-Y and Y-Z planes. The macro-indentation test provided a reliable estimate of the ultimate tensile strength (UTS-like) of the alloy. Other indentation properties gave inconsistent results, and a post factum analysis was, therefore, conducted, by means of a new approach, to account for the presence of residual stresses. The already existing indentation data were supplemented with new repeated indentation tests to conduct a detailed analysis of the relaxation ability of compressive and tensile residual stresses. The developed methodology allows the effect of residual stresses and the reliability of measured macro-indentation properties to be examined as a function of a small group of indentation parameters.

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.

Effect of Build and Scan Direction on Tensile Properties of Selective Laser Melted SS316L Alloy

Effect of Build and Scan Direction on Tensile Properties of Selective Laser Melted SS316L Alloy

Tribological analysis of laser deposited SS316L/Co27Cr6Mo functionally graded materials using adaptive neuro-fuzzy inference system

Image processing, power engineering, robotics, industrial automation etc., have all found successful uses for artificial intelligence (AI) techniques such as artificial neural networks (ANN) and neuro-fuzzy logic (FL). In this study, an adaptive neuro-fuzzy inference system (ANFIS) modelling of machine learning (ML) has been implemented to estimate the tribological properties of functionally graded materials (FGM). These FGMs were developed using a direct energy deposition (DED) technique of additive manufacturing (AM) from SS316L and Co27Cr6Mo alloys. The input data for this ANFIS modelling is acquired from the experiments done on FGM samples using the Pin on Disc (PoD) apparatus. The main objective of this work is to predict the tribological parameters of FGM samples by creating a data-driven predictive model called ANFIS. From the findings, the ANFIS was found to be the efficient method to estimate the wear rate of FGM samples.

Microstructure evolution and mechanical behavior of SS316L alloy fabricated by a non-toxic and low residue binder jetting process

The metal binder jetting technology has demonstrated tremendous potential for low-cost batch manufacturing. However, the hazardous nature of the most frequently used phenolic-based binders and their high residual content restrict the application of binder jetting. In this study, an environmentally friendly PVA-based binder with high water content (up to 80 %) was designed and adapted for most commercial nozzles. The developed binder with high wettability enabled good bonding between the powder layers. A fully dense SS316L part with low carbon and oxygen residuals was obtained by a continuous debinding-sintering treatment. Fine equiaxed grains were found in the sintered sample, leading to an isotropic tensile property with an ultimate tensile strength (UTS) of 535 MPa and an extremely high elongation of 53 %.

Micro-asperity tribocorrosion of CoCrMo, Ti6Al4V, and 316 stainless steel in air and physiological solution: Small scale reciprocal sliding of a single diamond tip

Fretting and corrosion of metallic medical devices are significant degradation mechanisms that impact performance. Multi-asperity contact surfaces undergo a progressive engagement-damage-redistribution process distributed over the nominal contact surface, implying that relatively short-lived fretting contact engagements of individual asperities are a central element to fretting corrosion processes in modular taper junctions of total hip replacements. In this work, the contact mechanics of single asperity hard-metal surfaces under small scale reciprocal sliding (SSRS) between two contacting surfaces in air and solution (i.e., tribocorrosion), typically less than 100 μm cyclic motion are presented and discussed for Ti–6Al–4V, CoCrMo, and 316L SS alloys. Characteristic scaling factors, based on asperity radius, hardness, and modulus, for characteristic stress and a dimensionless asperity radius are presented based on the interaction between elastic and plastic contact mechanics. The contact and tribological interactions of a 17 μm radius spherical diamond asperity was used to explore damage effects on these alloys in both air and phosphate buffered saline. The volume abraded, depth of penetration, extent of plastic deformation and oxide debris formation were captured as functions of cycles, load, and solution presence/absence. Damage was analyzed and quantified using digital optical microscopy, atomic force microscopy and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The results were analyzed with ANOVA statistics (α < 0.05). The extent of damage follows CoCrMo < Ti–6Al–4V < 316L SS. The wear characteristics varied significantly between alloys with more plastic deformation associated with CoCr and more shearing particle and ribbon formation present for Ti–6Al–4V and 316L SS. Solution immersion did not significantly increase volume loss for any alloy but did increase the amount of released and embedded oxide debris for 316L SS. Titanium also exhibited oxide debris generation and embedding. Importantly, significant (<5 μm) penetration depths were obtained after 100 cycles, indicating that single asperities, continuously engaged with metal under very low loads, rapidly generate extensive debris and plastic deformation.

Investigations on the effect of heat treatment on laser powder bed fusion built SS316L alloy

The present investigation aims at studying the changes happening in the mechanical and microstructural characteristics of additively manufactured Stainless Steel SS316L components post heat treatment. The samples printed through the Laser powder bed fusion based AM technique is considered for investigation. The samples are heat-treated at 650 °C and 1100 °C for 2 h and furnace cooled. The heat treatment is found to impart a substantial impact on the mechanical and microstructural characteristics of the component. The as-built SS316L sample possesses a micro-hardness value of 221.5HV, a tensile strength of 529 MPa, and total elongation of 28.5%. The heat treatment of samples at 1100 °C for 2 h lowers the micro hardness value (175.6HV), tensile strength (510 MPa) and increases the ductility (83.5%). The grain size, porosities and dislocation density are reduced during the heat treatment and the mechanical characteristics get modified. Hence, heat treatment can be considered as an effective method for altering the mechanical characteristics of the additively manufactured SS316L functional components.

On the Effects of High and Ultra-High Rotational Speeds on the Strength, Corrosion Resistance, and Microstructure during Friction Stir Welding of Al 6061-T6 and 316L SS Alloys

In this study, under the conditions of using tools at a high rotational speed (HRS) of 10,000 rpm and an ultra-high rotational speed (ultra-HRS) of 18,000 rpm, the produced welding heat input was utilized to weld two specimens of Al alloy 6061-T6 with 1.0 mm thickness and 316L SS with 0.8 mm thickness. The microstructural characteristics, mechanical properties, and electrochemical corrosion properties of the aluminum alloy–steel joints were analyzed. The higher tool offset forms an intermetallic compound layer of less than 1 µm at the Fe-Al interface on the advancing side (AS) at different speeds. This results in a mixed zone structure. The lower tool offset forms intermetallic compounds of only 2 µm. The formation of a composite material based on aluminum alloy in the weld nugget zone improves the hardness value. The intermetallic compounds are Fe3Al and FeAl3, respectively. It was observed that the formation of intermetallic compounds is solely related to the rotational speed, and the iron-rich intermetallic compounds produced under ultra-HRS parameters have higher corrosion resistance. When the tool offset is 0.55 mm, using the HRS parameters, the tensile strength is 220.8 MPa (about 75.9% of that of the base metal).

Electrophoretic Deposition Used to Prepare and Analyze the Microstructure of Chitosan/Hydroxyapatite Nano-Composites

This research studies the coating layer properties from chitosan and nano –hydroxyapatite made by pulsed electrophoretic deposition (PEPD) for biomedical applications. The 316L SS alloys were coated with hydroxyapatite in different solutions in 100 mL of suspension at a 30 V continuous voltage. To characterize the deposited coatings, X-ray diffraction spectroscopy (XRD), Fourier transform infrared (FTIR), Contact Angle, scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX),Yield deposition and Optical microscopy structural (OM) was used for coating layer, in addition to being calculated Zeta potential for suspensions. The aim of this study is to show that using the Pulsed EPD method at room temperature, a simple and low-cost solution for in situ synthesis of Nano -HAp within a chitosan matrix for biomedical applications can be demonstrated.

Effect of cladding of stellite-6 filler wire on the surface of ss316l alloy through cold metal arc transfer process

In this work, Cladding was done on SS316L alloy through the CMT process using Stellite-6 filler wire. 31 experiments were done at different welding conditions as per CCD matrix. The cladding specimens were characterized by macro and micro-study, Vickers microhardness evaluation and corrosion resistance analysis. An optical microscope, SEM-EDAX, and XRD were used to predict the structural characterizations, presence and the distributions of the elements. Based on the study higher voltage &amp; welding speed showed appreciable hardness at the interface &amp; cladding regions. The thickness of the interface was noted at a maximum of 190 μm. The EDS spectra showed that Fe, Cr and Co were the major elements in the clad and interface regions. The Co-rich phase and the low content of element O are found in the low corroded regions on the specimen. The maximum hardness observed at cladding and interface were 378 Hv and 270 Hv respectively.

In situ surface modification of stainless steel with hydroxyapatite using microwave heating

The present work involves enhancing the biocompatibility of austenitic stainless steel (SS-316L) implants by changing its surface composition and morphology through the microwave hybrid heating (MHH) technique. The polished SS-316L alloy surface layer was modified with bioactive hydroxyapatite (HAP) powder by utilizing an Industrial microwave oven operated at 2.45 GHz and 1.1 kW. The modified layer of SS-316L alloy was characterized in terms of phase analysis, microstructure investigation, porosity analysis and apatite forming ability. The microstructural investigation revealed that the presence of austenite dendrites with HAP along with some reaction induced phases like Fe3P, FeP, and Fe2P mainly in the inter-dendritic regions of the modified layer of SS-316L alloy. The microhardness of modified layer was higher than that of the unmodified layer of SS-316L alloy. The modified layer exhibited porosity in the range of 2% to 3%. The in-vitro study performed in simulated body fluid (SBF) solution indicates that the microwave-assisted surface modified layer of SS-316L alloy exhibited an improved bioactivity. The SEM images indicate the formation of apatite layer in the modified layer of SS-316L alloy. The observed biological improvements in the microwave-assisted modified layer was due to the cladding induced changes in the surface morphology and surface chemistry of the SS-316L substrate material.

Surface microtexturing of Ti-6Al-4V and SS316L alloys using high pulsed fiber lasers for improving the adhesive bonded performance

This study presented the high pulsed fiber laser texturing on Ti-6Al-4V and SS316L alloy substrates to enhance their adhesive bonding strength of heterogeneous materials for the industrial applications. Optical spectrum, surface morphology, cross-sectional profile, surface roughness, and water contact angle (WCA) of laser-textured alloy surfaces were measured using a spectrophotometer, a confocal laser scanning microscope, and a contact angle analyzer. Moreover, the shear strength of adhesive bonding laser-textured Ti-6Al-4V and SS316L alloy joints was tested using a universal testing machine. Before laser texturing, the optical absorbance of Ti-6Al-4V substrates was slight high than that of SS316L ones at the 1064 nm fiber laser waveband. The laser-textured Ti-6Al-4V alloy substrates had varied coloring and significant microstructures compared with laser-textured SUS316 ones. The minimum WCAs of laser-textured Ti-6Al-4V and SS316L alloy substrates were 17.8 ± 1.5° and 25.2 ± 2.9° as the laser average power and scanning speed were 13.1 W and 300 mm/s and 5.1 W and 100 mm/s, respectively. Furthermore, the maximum fracture load of adhesive-bonded laser-textured Ti-6Al-4V and SS316L alloy joints with minimum WCA surfaces was three times more than that of ones with un-textured surfaces.