AISI 316L SS Research Articles

Friction Welding of Titanium to 304L Stainless Steel Using Interlayers

Abstract Friction welding of commercially pure titanium to austenitic stainless steel (AISI 304L SS) using intermediate layers was studied. The interlayers used were commercially pure nickel, tantalum and vanadium in the form of thin foils. The interlayers were aimed at avoiding direct contact between the base materials which may otherwise lead to formation of mainly Ti-Fe intermetallic phases at the interface which may seriously affect the weld properties. Interlayer foils were used individually and in combination (nickeltantalum and nickel-vanadium) suitably called in the present work as single and double interlayer joint systems respectively. Same interlayer behaved differently with respect to extrudability in these two systems. All the joints showed moderate strengths in tensile test. However, joints with single interlayer exhibited poor bend ductility, and double interlayers improved it to about 40°. Microhardness studies revealed a peak in nickel single interlayer system alone, confirming presence of hard phases at the interface.

SIMS analysis of hydrogen content in near surface layers of AISI 316L SS after electrolytic polishing under different conditions

Hydrogen concentration in AISI 316L stainless steel samples was monitored perpendicularly to the flat sample surface up to the depth of 0.8 μm, using secondary ion mass spectrometry (SIMS). Depth profile analysis was performed on the samples after electrolytic polishing under different conditions. Analyses were performed on SAJW-05 apparatus with quadrupole Balzers QMA-410 analyzer and Physical Electronics 06-350E ion gun. 5 keV Ar + primary ion beam of 100 μm diameter was scanned over 1 mm × 0.8 mm area. Positive (H +, C +, CH +, O +, Cr +, Fe +) and negative (H −, C −, CH −, O −, OH −, CrO −, FeO −) secondary ion emission was registered from central part of the scanned area (10% of area) during primary ion beam sputtering. Results of hydrogen depth profile analysis were compared for the samples after a conventional electrochemical polishing (EP), and magnetoelectropolishing (MEP). Both EP and MEP processes were carried out under the electrochemical conditions regarding also natural and forced convection. The steel samples taken of a hot-rolled sheet, as received (AR), and after abrasive polishing (MP), were used as a reference. Results show that the increased current density (up to 200 A/dm 2) and electrolyte stirring during electropolishing cause lowering of the hydrogen content in the samples, with the best result regarding hydrogen content decrease obtained on MEP200 sample. In fact, within the MEP process, characteristic with the self-contained electrolyte whirling, the contents of hydrogen are significantly decreased.

Characterization of Plasma Sprayed Hydroxyapatite Coatings on AISI 316L SS and Titanium Substrate and their Corrosion Behavior in Simulated Body Fluid

In order to increase the bone bioactivity of metallic implants, hydroxyapatite (HA: Ca10(PO4)2(OH)6) is often coated on their surface so that real bond with surrounding bone tissue can be formed. In present study, HA coatings were deposited on AISI 316L SS and titanium using shrouded plasma spray process. The coated specimens were subjected to X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FE-SEM/EDAX). The polarization studies in simulated body fluid (SBF) were conducted to evaluate the corrosion resistance of bare and coated specimens. It was found that the hydroxyapatite coating provided excellent corrosion resistance. The resistance to corrosion was found independent on substrates

Investigation of selected surface properties of AISI 316L SS after magnetoelectropolishing

The aim of the paper is to present the surface film composition formed on AISI 316L SS and its surface microhardeness after electropolishing (EP) and magnetoelectropolishing (MEP) in a wide range of the process conditions. The electropolishing EP process has been performed under natural convection (in still electrolyte), and under a forced convection (moderate stirring below 0.1 m/s), both on the polarization plateaux and much above it. Another series of experiments was carried out on AISI 316L SS samples prepared by MEP at 350 mT. The samples prepared by mechanical abrasive polishing, with the grit size up to 1000, served as a reference. First of all, concerning the surface film composition, a big difference in iron contents was observed between the samples after mechanical polishing and electropolishing. On the other hand, there were much less differentiations of chromium contents in surface film formed on 316L SS samples after each of the studied electropolishing conditions, and even mechanical polishing. The total Cr:Fe ratio was also studied, with quite promising results obtained. At the end the conclusions concerning the selection of proper electropolishing conditions have been formulated.

Effect of Temperature on Galvanic Corrosion of Non-Welded/Welded AISI 316L Stainless Steel in H3PO4

Galvanic corrosion of non-welded/welded AISI 316L SS at different temperatures (25 ºC to 60 ºC) at a Reynolds number of 1456 in phosphoric acid has been studied using polarization curves (by the mixed potential theory) and zero resistance ammeter (ZRA) measurements. Imposed potential measurements provide more active predicted coupled potentials and higher galvanic current densities than those obtained using ZRA measurements. Polarization curves show that the anode of the pair is the non-welded AISI 316L. Galvanic current density values obtained from polarization curves increase with temperature. ZRA tests present the highest iG values at 60 ºC; however, the values are very close to zero for all the temperatures studied. This is in agreement with the low value of the compatibility limit and of the parameter which evaluate the Galvanic phenomenon importance. Both techniques present the most positive potentials at the highest temperature.

Experimental Evaluation of Corrosion and Hardness on AISI 316l Stainless Steel Implanted with Nitrogen and Argon Ions

In this work the AISI 316L SS was implanted with two different ions namely nitrogen and argon separately at 100 KeV with fluence of 1×1017ions/cm2 at room temperature. The crystallographic orientation and surface morphology were studied using X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The effects of ion implantation, on the corrosion performance of AISI316L stainless steel were evaluated. Microhardness was also measured by Vickers method by varying the loads. The results of the studies indicated that there was a significant improvement in both corrosion and hardness in the case of implanted samples.

Analysis of XPS results of AISI 316L SS electropolished and magnetoelectropolished at varying conditions

Abstract The aim of the paper is to present the surface film composition formed on AISI 316L stainless steel after electropolishing (EP) and magnetoelectropolishing (MEP) for a wide range of the process conditions. The electropolishing EP process has been performed under natural convection (in still electrolyte), and under a forced convection (moderate stirring below 0.1 m/s), both at the polarization plateaux and much above it. Another series of experiments were carried out on AISI 316L SS samples prepared by MEP at 350 mT. The samples prepared by mechanical abrasive polishing, with the grit size of 1000 served as a reference. The Cr:Fe ratio was also studied for the differently prepared samples and it was found that this ratio was significantly higher for the EP and MEP samples than the mechanically polished one. Based on the results, the selection of proper electropolishing conditions have been formulated.

Experimental investigation on corrosion and hardness of ion implanted AISI 316L stainless steel

The AISI 316L stainless steel has been widely used both in artificial knee and hip joints in bio-medical applications. In the present study AISI 316L SS was implanted with two different ions: nitrogen and helium at 100 keV with a dose of 1 × 10 17 ions/cm 2 at room temperature. The crystallographic orientation and surface morphology were studied using X-ray diffraction (XRD) and scanning electron microscope (SEM). The effects of ion implantation on the corrosion performance of AISI 316L stainless steel was evaluated in 0.9% NaCl solution using electro chemical test both on the virgin and implanted samples. The subsequent Tafel analysis shows that the ion implanted specimens were more corrosion resistant when compared to the bare specimens. Microhardness was also measured by Vickers method by varying the loads. The results of the studies indicated that there was a significant improvement in both corrosion resistance and hardness of implanted samples.

Corrosion Behavior of Mild Steel and SS 304L in Presence of Dissolved Copper

The failure of steel components in multistage flash (MSF) desalination or power plants as a result of the deposition of carryover heavy metals/oxides is a common problem and reported by many authors. The present investigation was undertaken to study the corrosion behavior of mild steel and AISI 304L SS in presence of dissolved Cu ions under different experimental conditions. The experimental conditions include: variation in aqueous medium, Cu ion concentration, pH and flow condition. The corrosion rate of mild steel and SS 304L in presence of different concentration of Cu was determined by weight loss measurements and solvent analysis of iron ions into the test solution after completion of immersion. The amount of Cu ions present in the test solution after completion of immersion was also estimated using Atomic absorption spectrophotometer. The pH of the test solution was monitored during the entire period of immersion. Electrochemical techniques like free corrosion potential measurements and potentiodynamic polarization measurements were carried to find out the role of Cu ions on the corrosion behavior of mild steel and SS 304L. The effect of Cu on corrosion rate of mild steel is quite pronounced and follows interesting trend. However, SS 304L is not affected either in distilled water or artificial seawater and do not show any significant variation in corrosion rates in presence of Cu ions.

Effect of different micro-plasma arc welding (MPAW) processes on the corrosion of AISI 316L SS tubes in LiBr and H 3PO 4 solutions under flowing conditions

This work studies the corrosion under flowing conditions of four kinds of AISI 316L materials welded by the micro-plasma arc welding technique in different media: a basic (LiBr) and an acidic (H 3PO 4) solution by means of polarization measurements. Sensitization tests, galvanic corrosion evaluation, microstructural analyses and microhardness tests have been also carried out. Corrosion parameters revealed that, among the materials welded with backing gas, the alloy which presented better corrosion behaviour was the one welded without filler alloy. However, this kind of material could undergo several corrosion problems if a crack is formed or due to an inadequate joint penetration.

Austenite modification of AISI 316L SS by pulsed nitrogen ion beams generated in dense plasma focus discharges

Abstract We present the results of a surface modification of AISI 316L stainless steel by surface irradiation with high energy, pulsed nitrogen ion beams generated with 0.8 kJ dense plasma focus. The surface characterization was done using GAXRD, Auger electrons spectroscopy, TEM and optical microscopy. After the irradiation, we found a modification of a 1 μm thick surface layer, on which a gradual lattice expansion of the austenite with the number of irradiation pulses, i.e. with the total nitrogen ion fluence, was observed. In addition, ~ 40 nm close to the surface layer, a disordered lattice structure had been observed through TEM analysis. Those results can be explained in terms of the extreme thermal effect induced on the surface through the fast high energy release during the pulsed ion interaction with the steel surface, followed by an also rapid cooling down process which limits the nitrogen diffusion to the bulk.

Properties and corrosion behaviour of reactive magnetron sputtered TiAlN coatings on AISI 316L SS in simulated bodily fluid

Because of their superior properties, titanium aluminium nitride (TiAlN) films are increasingly applied as protective layers on cutting and forming tools and turbine compressor blades and as biocompatible barriers. TiAlN films were deposited on AISI 316L stainless steel substrates by reactive magnetron sputtering using a target consisting of equal segments of titanium and aluminium. X-ray diffraction characterisation showed that the coating structure was face centred cubic. AFM and SEM studies indicated that the coatings are regular with dense shpherical granular structure. The coatings were also characterised using photoluminescence spectroscopy and Raman microscopy to elucidate the optical and acoustic phonon modes of the cubic lattices. Characteristic peaks were observed at 250, 620 and 1180 cm−1 in laser Raman studies. Polarisation and impedance spectroscopy studies on TiAlN and TiN coated specimens were conducted in Fusuyama simulated body fluid. The charge transfer resistance Rct increased in the order: uncoated 316L substrate; 2 μm TiN film; 3 μm TiN film; 2 μm TiAlN film. Thus, the TiAlN coating has the highest corrosion resistance, and was also found to have the most noble corrosion potential and lowest corrosion rate in the polarisation tests.

Effect of loading history on the threshold stress in the creep deformation of an austenitic stainless steel

The steady state creep rate of AISI 316L(N) SS at 923 K can be described by the threshold stress compensated power law relationship. The threshold stress for creep deformation over the stress range 142–230 MPa has been evaluated graphically as 60 ± 10 MPa from the conventional creep tests. A threshold stress of about 110 MPa was computed from two stress decrease tests which is much higher than that obtained from conventional creep tests. The higher apparent threshold stress has been rationalized by invoking the effect of dislocation cell structure on the constant A in the steady state creep rate equation. A stress change test wherein the stress was progressively increased yielded a threshold stress identical to that obtained from the conventional creep tests. This implies that the steady state structure at a particular stress is path independent so long as the preceding stresses are lower. The dislocation substructure indicates that the creep deformation proceeds by the dislocation network mechanism. The threshold stress for this mechanism represents the stress for the activation of dislocation links constituting the Frank network.

Hydrogen Peroxide Decomposition in an Environmentally Friendly Pickling Solution for AISI 316L Stainless Steel

Abstract There is increasing interest in the utilization of ecological bath solutions for the pickling of stainless steel (SS), because conventional nitric (HNO3) and hydrofluoric (HF) acid mixtures generate high NOx emissions. A mixture of hydrogen peroxide (H2O2), sulfuric acid (H2SO4), and HF has been tested in this study as an environmentally friendly pickling solution for AISI 316L SS (UNS S31603). The decomposition of H2O2 and the H2SO4-HF-H2O2 mixture was assessed at different temperatures from 25°C to 60°C, with ferric ion contents from 0 to 40 g/L, with and without stirring of the aqueous acid mixture. The p-Toluene sulfonic, 3-hydroxybenzoic, and 4-dodecylbenzene sulfonic acids were tested as stabilizers for H2O2. The AISI 316LSS pickling rate found at 50°C was 2.35 × 103 mg/dm2-day (mdd) and 0.12 × 103 mdd, respectively, in the absence and presence of 40 g/L ferric ion.

Friction and wear behaviour of implanted AISI 316L SS and comparison with a substrate

Ion implantation creates alterations in surface composition or morphology of solids which yield to a modification of physical and especially mechanical properties; such as hardness and modulus of elasticity. The aim of this study is to focus on the friction and wear behaviour of N 2 and Zr implanted and TiN coated 316L stainless steel and compare with a substrate. Particularly, stainless steels were of interest, because they often display a poor tribological behaviour, which can be improved when they are hardened by incorporating N 2, TiN and Zr and forming a hardened surface zone. The present implantations were shown to improve the friction coefficient as well as the wear resistance of the stainless steel surface.

In vitro corrosion behavior of bioceramic, metallic, and bioceramic–metallic coated stainless steel dental implants

Objectives: The most common metals and alloys used in dentistry may be exposed to a process of corrosion in vivo that make them cytotoxic. The biocompatibility of dental alloys is primarily related to their corrosion behavior. The aim of this work was to evaluate the corrosion behavior and thus the biocompatibility of the uncoated and coated stainless steels and compare the effect of type of coatings on corrosion behavior. Methods: Three types of coatings, hydroxyapatite (HA), titanium (Ti), and a double-layer HA/Ti on AISI 316L stainless steel were made. HA coating was produced using plasma-spraying technique and Ti coating was made using physical vapor deposition process. In order to perform a novel double-layer composite coating, a top layer of HA was plasma-sprayed over a physical vapor deposited Ti layer on AISI 316L stainless steel. Structural characterization techniques including XRD, SEM and EDX were used to investigate the microstructure, morphology and crystallinity of the coatings. Electrochemical potentiodynamic tests were performed in physiological solutions in order to determine and compare the corrosion behavior of the coated and uncoated specimens as an indication of biocompatibility. Results: Double-layer HA/Ti coating on AISI 316L SS had a positive effect on improvement of corrosion behavior. The decrease in corrosion current densities was significant for these coated specimens and was much lower than the values obtained for uncoated and single HA coated specimens. Ti coating on AISI 316L SS also has a beneficial effect on corrosion behavior. The results were compared with the results of corrosion behavior of HA coated commercially pure titanium (cpTi) and uncoated cpTi. Significance: These results demonstrated that the double-layer HA/Ti coated 316L SS can be used as an endodontic implant and two goals including improvement of corrosion resistance and bone osteointegration can be obtained simultaneously.

Susceptibility to Stress Corrosion Cracking of 254SMO SS

The susceptibility to stress corrosion cracking (SCC) of solubilized and sensitized 254SMO SS was studied in sodium chloride, and sodium fluoride solutions at 80 °C and sulfuric acid solutions in presence of sodium chloride at 25 °C. The influence of salt concentration, pH values and the addition of thiosulfate was examined. The susceptibility to SCC was evaluated by Slow Strain Rate Tests (SSRT), at 1.5 x 10-6 s-1 strain rate. The behavior of 254SMO was compared to those of AISI 316L SS and Hastelloy C276. 254SMO showed an excellent resistance to SCC in all conditions, except in the more acidic solutions (pH <= 1) where, in the sensitized conditions, intergranular stress corrosion cracking occurred.

Analysis of a premature failure of welded AISI 316L stainless steel pipes originated by Microbial induced corrosion

AbstractThis paper analyses the causes of the premature failure call welded AISI 316L stainless steel (ss) pipes which formed part of a sea water cooling circuit. The service time of the pipes was 8 months. The laboratory tests carried out consisted of metallography tests, δ‐ferrite determination, intergranular corrosion susceptibility, cyclic anodic polarization curves, scanning electron microscopy (SEM), energy dispersive X‐ray (EDX) and X‐ray photo‐electron spectroscopy (XPS). The study presents typical forms of microbial induced corrosion (MIC) in AISI 308L and 316L ss in contact with natural sea water. The research is completed with the performance of bacteriological tests which demonstrate that the bacteria which cause the localized corrosion are of the sulphate‐reducing genus “desulfovibrio” and the sulphide‐oxidizing genus “thiocapsa”.

Corrosion of stainless steels and nickel-based alloys for alkaline water electrolysis

The corrosion behaviour of commercial austenitic stainless steels and nickel-based alloys in 38wt% KOH solutions was investigated between 120° and 180°C under hydrogen and oxygen overpressure. (a) In hydrogenated solutions, alloys containing 20% Ni or more are resistant to general corrosion and to stress corrosion cracking. (b) In oxygenated solutions, type AISI 304L SS are highly corroded and susceptible to SCC. Nickel-based alloys are resistant to SCC, but the general corrosion rate is high beyond a break-away point. Among these two types of materials, the most resistant alloys are found to be type 310(L) SS and Alloy 800. Taking into account SCC results, Alloy 800 is the best choice for water electrolysis within the temperature range 120°–150°C. The different materials tested are not resistant enough to corrosion at 180°C and even nickel is not satisfactory at this temperature.