AISI 316L Stainless Steel Substrates Research Articles

Microstructural Evolution and Wear Resistance of Surface Alloyed AISI 316L Stainless Steel with Equi-atomic CoCrFeMnTi by Continuous Wave Diode Laser

In this investigation, a multicomponent alloyed surface was developed on AISI 316L stainless steel (AISI 316L SS) substrate by melting it with a fiber coupled diode laser having 3.6 mm beam diameter (using argon as shrouding gas) along with simultaneous melting of equiatomic pre-mixed elemental powders of cobalt (Co), chromium (Cr), iron (Fe), manganese (Mn) and titanium (Ti) (high entropy alloy). The process parameters used in the experiment were laser power (1800–2200 W) and scan speed (6 mm/sec to 8 mm/sec). Following laser surface alloying (LSA) a detailed microstructural characterization of the surface and evaluation of surface mechanical properties (micro/nano hardness, Young’s modulus and wear resistance) were undertaken. Due to LSA there is formation of near eutectic microstructure consisting of FCC and BCC phase mixtures along with the precipitates of Fe2Ti randomly distributed in the microstructure which was confirmed by X-ray diffraction (XRD) and electron back scattered diffraction (EBSD) analysis. There is an increase in microhardness in the processed zone from 180 VHN (of as received AISI 316L SS) to 309–650 VHN. In addition, there is an increase in Young’s modulus from 208 GPa for as received AISI 316L SS to 228–301 GPa for laser surface alloyed zone. The wear resistance (against WC ball in fretting wear mode) property of AISI 316L SS substrate after LSA was superior to the substrate. The wear mechanism was established.

Effect of alloy 625 buffer layer on corrosion resistance of nickel base hardfacing

Nickel base hardfacing alloys serve to mitigate corrosion losses at elevated temperatures. Efficacy of Nickel base hardfacing alloys can be compromised when applied onto Fe base substrates due to iron dilution in hardfacing. The degree of Fe dilution can be reduced by using advanced deposition methods and optimized deposition parameters. Gas Tungsten Arc Welding (GTAW) method is commonly employed for its cost-effectiveness and versatility, but it tends to induce higher Fe dilution due to increased heat input. This study aims to reduce the degree of Fe dilution and enhance corrosion resistance by introducing a nickel base buffer layer (alloy 625) between the nickel base hardfacing alloy and AISI 316L stainless steel substrate. For comparative purposes, Ni base hardfacing alloy was deposited on the substrate without any buffer layer. Hardfacing depositions were prepared using manual GTAW process. Process parameters namely, deposition current, voltage, travelling speed, pre-heating temperature, and cooling method were kept constant. Samples underwent aging at 1123 K for 4 h, followed by microstructural examination via optical and scanning electron microscopes. Iron (Fe) dilution quantification was performed using energy dispersive spectroscopy (EDS). The EDS analysis showed that the use of buffer layer between the hardfaced deposit and the substrate decreased the degree of Fe dilution in the hardfaced deposit. X-Ray diffraction (XRD) analysis was performed to identify various phases formed in the hardfaced deposit. Potentiodynamic polarization test was performed to assess the corrosion resistance of hardfaced deposit in 3.5 wt% NaCl solution. Results show significant improvement in corrosion resistance of hardfacings deposited sample with buffer layer as compared to those without buffer layer. Aging treatment further enhanced corrosion resistance. The corrosion resistance data is correlated with the microstructure and phases formed in various samples.

Electrophoretic Deposition of ZnO-Containing Bioactive Glass Coatings on AISI 316L Stainless Steel for Biomedical Applications

The main objective of this investigation was to study the implications of incorporating zinc oxide nanoparticles into the matrix of a bioactive glass for the bioactivity and structural properties of the deposited coating. ZnO-containing bioactive glass was coated on an AISI 316L stainless steel substrate using the electrophoretic deposition technique. AISI 316L stainless steel is a biomedical grade steel, which is widely used in different biomedical applications. For the electrophoretic deposition, voltages and times were chosen in the range of 15–40 V and 15–120 min, respectively. The microstructure, phase composition, and surface roughness of coated samples were analyzed in this investigation. Moreover, the corrosion behavior and the MTT (mitochondrial activity) of samples were studied. Results showed a uniform distribution of elements such as silicon and calcium, characteristic of bioactive glass 58S5, in the coating as well as the uniform distribution of Zn inside the ZnO-containing samples. The findings showed that the deposited ZnO-containing bioactive glass is a hydrophilic surface with a relatively rough surface texture. The results of the MTT and antibacterial effects showed that the deposited layers have promising cell viability.

Crystalline Structure, Morphology, and Adherence of Thick TiO2 Films Grown on 304 and 316L Stainless Steels by Atomic Layer Deposition

Titanium dioxide (TiO2) thin films are widely used in transparent optoelectronic devices due to their excellent properties, as well as in photocatalysis, cosmetics, and many other biomedical applications. In this work, TiO2 thin films were deposited onto AISI 304 and AISI 316L stainless steel substrates by atomic layer deposition, followed by comparative evaluation of the mixture of anatase and rutile phase by X-ray diffraction, Raman maps, morphology by SEM-FEG-AFM, and adhesion of the films on the two substrates, aiming to evaluate the scratch resistance. Raman spectroscopy mapping and X-ray diffraction with Rietveld refinement showed that the films were composed of anatase and rutile phases, in different percentages. Scratch testing using a diamond tip on the TiO2 film was employed to evaluate the film adherence and to determine the friction coefficient, with the results showing satisfactory adherence of the films on both substrates.

Direct Energy Depositions of a 17-4 PH Stainless Steel: Geometrical and Microstructural Characterizations

Direct energy deposition (DED) is a widely accepted additive manufacturing process and a possible alternative to the subtractive manufacturing processes due to its high flexibility in fabricating new 3D parts. DED enables the manufacture of complex parts without using costly and time-consuming conventional processes, even though building parameters need to be accurately determined. In the present investigation, the effect of different process parameters on geometrical features, quality, microstructure, and microhardness of 17-4 PH stainless steel single tracks deposited onto an AISI 316L stainless steel substrate was investigated. Four sets of process parameters, considering different values of laser power, scanning speed, and powder feed rate, were selected in the manufacturing strategy, and specimens drawn from each single-track deposition were analyzed by stereomicroscopy, optical microscopy (OM), scanning electron microscopy (SEM-EDS), and X-ray diffraction (XRD). The results show that the optimized geometrical features of the track, together with the best microstructural and hardness properties, were obtained with the highest values of the laser energy input.

Mechanical characterization of tin coatings with biomedical application in elbow prostheses

The present work aims to study TiN films deposited on AISI 316L stainless steel substrates by physical vapor deposition through the Magnetron Sputtering technique with CD, heating it at a temperature of 200º and a constant time of 30 min. Identifying the mechanical properties to be used in biomedical applications, the microstructural characterization was performed by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). Adhesion tests were performed under the VDI 3198 standard. Tribological wear tests were performed using a 6 mm chromium plated steel pin (AISI 52100) on coated and uncoated substrates to study and compare the sliding effect continuing the same circumferential geometry, with a stroke length of 200 m and a load of 5N in wet and dry way using milli-Q water to simulate biological fluids in order to test the performance and durability of the implant.

Thin films of Titanium Nitride deposite on substrates used for biomedical applications

In the present work, thin films of TiN were obtained on AISI 316L stainless steel substrates by DC unbalanced magnetron sputtering with promising characteristics such as resistance to wear and corrosion to be used in biomedical applications by changing the temperature of the substrate and the mixture. of gases. Microstructural characterization was performed using optical microscopy, atomic force microscopy, and scanning electron microscopy (SEM). Scratch tests were performed using an irradiated and non-irradiated ultra-high molecular weight polyethylene (UHMWPE) pin on the coated and uncoated substrates to study and compare the scratch effect, continuing the same circumferential geometry, a stroke length of 200 m and a 5N wet load using pure Milli-Q water (type 1) to simulate body fluids with the pin to test its performance and implant durability showing higher values in the coefficient of friction (COF) in the TiN-coated samples.

The effect of martensitic transformation on the cavitation erosion resistance of a TIG-deposited Fe-Cr-C-Al-Ti layer

This study shows the effect of strain-induced martensitic transformation (austenite (γ)–to–martensite (α′)) on the cavitation erosion resistance of a Fe-Cr-C-Al-Ti deposited layer with a high share of metastable austenite in the structure. For comparison, the cavitation erosion of a E308L-17 deposited layer and an AISI 316L stainless steel substrate was also evaluated. Cavitation tests were performed using a modified ultrasonic tester. X-ray diffraction (XRD) was used to examine martensitic phase transformation. An optical microscope (OM), a scanning electron microscope (SEM), and a 3D optical profilometer were utilized to evaluate the eroded specimens' surfaces. The chemical composition of the Fe-Cr-C-Al-Ti deposited layer was analyzed using an energy-dispersive microanalysis system (EDS). The cavitation results revealed that the Fe-Cr-C-Al-Ti specimen exhibited a resistance to cavitation erosion approximately 4 and 10 times higher than the E308L-17 and AISI 316L specimens, respectively. As shown, effects of γ → α′ transformation were mainly responsible for the results.

Tribological Properties of Ti-Doped Diamond-Like Carbon Coatings Under Boundary Lubrication With ZDDP

Abstract Diamond-like carbon (DLC) coatings containing 0.7%, 5.8%, and 23.3% Ti were deposited via pulsed cathodic arc deposition and magnetron sputtering on AISI 316L stainless steel substrates. The varied Ti content was controlled by setting Ti target current at 3, 5, and 7A. The composition, microstructure, mechanical, and tribological properties of Ti-doped DLC (Ti-DLC) coatings were investigated using X-ray photoelectron spectroscopy, Raman spectroscopy, nanoindentation, and ball-on-disc tribometer. The results show that TiC formed when Ti content in the coating was higher than 5.8 at% and the ID/IG ratios increased gradually with the increasing Ti content. Ti-DLC with 0.7 at% Ti had the highest H/E and H3/E2 ratios and exhibited optimal tribological properties under lubrication, especially when zinc dialkyldithio-phosphate (ZDDP) was contained in the oil. Furthermore, ZDDP tribofilms played an important role in wear reduction by protecting the rubbing surfaces against the adhesion and suppressing the tribo-induced graphitization of DLC coatings.

MD-Simulation of Duty Cycle and TaN Interlayer Effects on the Surface Properties of Ta Coatings Deposited by Pulsed-DC Plasma Assisted Chemical Vapor Deposition

In this work, molecular dynamics (MD) simulations were employed to investigate the effects of duty cycle changes and utilization of tantalum nitride interlayer on the surface roughness and adhesion of Ta coating deposited by pulsed-DC plasma assisted chemical vapor deposition. To examine the simulation results, some selected deposition conditions were experimentally implemented and characterized through scanning electron microscopy, atomic force microscopy (AFM) and microscratch tests. The Ta and Ta/TaN coatings were deposited on AISI316L stainless steel substrate in a plasma atmosphere consist of Ar, H2, N2 and TaCl5 vapor at 350 °C. The results showed that at the same duty cycles the surface roughness of Ta/TaN coating is at least 40% less than that of the single layer Ta coating. By increasing the duty cycle from 17 to 40%, the surface roughness significantly decreases about 80%. This is attributed to the further exposure of surface against high energy ions bombardment at higher duty cycles. The presence of TaN interlayer due to its lower lattice mismatch with Ta (under 2%), contributes to the nucleation of Ta grains which consequently leads to reducing the surface roughness. The enhanced adhesion of the Ta coatings on TaN is discussed in view of improving the interfacial stresses as shown by the MD simulations. The MD simulations results were shown to be in good agreement with the experimental data.

Corrosion behavior of tantalum coatings on AISI 316L stainless steel substrate for bipolar plates of PEM fuel cells

Corrosion resistance of tantalum coatings 30 μm thick deposited by chemical vapor deposition on SS316L coupons has been evaluated by electrochemical impedance spectroscopy (EIS). To this end, anodic and cathodic operating conditions of proton exchange membrane fuel cells (PEMFC) have been simulated in a three-electrode heated corrosion cell. Interfacial contact resistance (ICR), contact angle and durability tests have been performed in long-term tests (>100 h) polarizing the electrode to 1.193 V vs. Ag/AgCl. Results obtained by different experimental techniques show a dense coating structure with a high polarization resistance, mainly formed by surface crystals of α-Ta (bcc), Ta2O5 and carbon. An atomic ratio (in %) of oxide to metallic species (Taox/Tamet) of 4.8 was verified from XPS spectra, which is slightly increased to 6.23 after the anodizing treatment. The modified surface composition yielded a coating capacity higher than the amorphous oxide, favoring the in-plane electrical conduction. After the treatment, no noticeable changes were observed neither in surface morphology nor in contact angle (>90°). ICR values in the range of 22.3–32.6 mΩ cm2 were obtained for a clamping pressure of 140 N cm−2. No morphological changes or loss of coating adherence were observed during the long-term tests.

Deposition and characterization of a sol-gel Mg-substituted fluorapatite coating with new stoichiometries

The calcium substitution for magnesium on fluorapatite is attractive because this element is a natural substitute in biological apatites. There are several published stoichiometries for calcium substituted by magnesium fluorapatites and most works point out that the formation and fixation of biomimetic Ca-P coatings in Ringer’s solution were strongly related to Mg2+ content and furthermore the Mg replacement improves the bioactivity of apatite. In the present study, fluorapatite (FA) and fluorapatite substituted with 6% and 7% of magnesium were obtained by deposition via sol-gel coating on substrates of AISI 316L stainless steel to investigate the effect of magnesium substitution on fluorapatite with not yet investigated stoichiometry. Characterization of coating thickness, chemical composition and crystalline structure was performed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The coating adhesion was evaluated using the pull-out test and the corrosion resistance was undertaken using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The electrochemical results showed improvement in the corrosion resistance of magnesium-fluorapatite compared to fluorapatite coated on AISI 316L stainless steel substrates. The improvement corrosion protection and adhesion performance indicate that such magnesium fluorapatites coatings are very interesting candidates as bioactive coatings for implants.

Adhesion and Corrosion of Ti, TiN and TiCrN Films Deposits on AISI 316L in SBF Solution

Abstract. In the present work several films of Ti, TiN, and TiCrN have been coated on AISI 316L stainless steel substrates using magnetron sputtering techniques, in order to improve their surface properties. The morphology and structure of the coatings were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical performances skills in an SBF solution and the adhesion of these deposits were studied to understand these behaviors. From the results it was shown the TiCrN deposition presents the lowest corrosion resistance in the SBF solution, while TiN deposit is the most resistant to corrosion resistance in the same solutions, but its critical load (Lc3-TiN), is relatively low and has a risk of delamination which can limit its use. On the other hand, the Ti deposit exhibits a high resistance to corrosion and a high passivation (icorr (Ti) = 0.57 µA.cm-2 and Rp (Ti) = 67.98 KW.cm2). The critical load (Lc3-Ti = 43.38 N), the crack propagation resistance (CPRs-Ti = 81.64 N) and the scratch hardness (HSL-Ti = 125.75´1012 Pa) also testify to its high adhesion to the AISI 316L substrate. Thus the Ti deposit has proved to be the most favorable protective coating for AISI 316L stainless steel in SBF solution.

Multipass and reciprocating microwear study of TiN based films

Titanium nitride (TiN) coatings with a Cr metallic interlayer were deposited on AISI 316L stainless steel substrates using D. C. unbalanced magnetron sputtering, changing substrate temperature and gas mixture. The effect of the sliding motion in wear tests was studied, comparing multipass (unidirectional) and reciprocating (bidirectional) sliding modes. In addition, microstructure, mechanical properties and adhesion were analyzed. The structural characterization was performed by scanning electronic microscopy (SEM) and grazing incidence X-ray diffraction (GIXRD). Moreover, hardness of the coating was measured by spherical nanoindentation, and thermal residual stresses were estimated. The scratch tests were conducted using a steel ball of 1 mm of diameter. To study the effect of sliding motion, the wear tests were carried out with an alumina ball of 3 mm of diameter, in both sliding modes the same linear test geometry, a stroke length of 3 mm and loads of 0.5 and 1 N were used. TiN coatings thicknesses ranged from 1.1 to 1.8 μm, growing in preferred orientations (200) and (111). It was found that increasing the nitrogen content during the deposition cause a decrease in the adhesion of the coating. In the sliding wear tests, the coefficient of friction (COF) values ranged from 0.12 and 0.22. The effect of sliding motion in COF was more evident in the tests performed with 0.5 N load, reciprocating exhibited higher values than multipass. The specific wear coefficients k varied from 6.9 × 10−4 to 1.88 × 10−3 mm3 · N−1m−1 for all tests, the highest value was obtained in a reciprocating test.

Diamond-like carbon-deposited films: a new class of biocorrosion protective coatings

A series of diamond-like carbon thin films was applied on AISI 316L stainless steel substrates through a pulsed-direct current plasma-enhanced chemical vapor deposition technique to study the effects of working parameters (bias voltage and deposition pressure) on the microstructure and biocorrosion resistance of films. Raman spectra indicated that under low bias voltage and higher deposition pressure, the films possess a higher amount of sp2structure, lower internal stress and an improved biocorrosion resistance due to a smooth and defect-free morphology. The lamellar sp2structure blocked a penetration of corrosive entities. The oxygen content of locally corroded areas (∼11·9 wt.%) was much higher than that of non-corroded areas (2·6 wt.%) corroborating galvanic corrosion between carbide and nitride phases. Moreover, by increasing the deposition pressure from 20 to 40 Pa, the internal stress decreased from 1·03 to 0·82 GPa. The results confirmed that it is possible to tailor the properties of the coatings such as structural composition and particularly biocorrosion resistance by the control over the working parameters. Such anticorrosive diamond-like coatings could benefit biomedical implants used for tissue regeneration.

Nanostructural characterization of sputter deposited Ti-Nb coatings byautomated crystallographic orientation mapping

AISI 316 L stainless steel (SS) and CrCo alloys are commonly used for manufacturing biomedical implants due to their reasonably adequate bulk properties. Commercially pure (CP) Ti and its alloys are more biocompatible, but also significantly more expensive, than SS and CoCr alloys; they have an additional advantage compared to SS and CoCr alloys: their elastic modulus values are more compatible with those of the human bones (10–40 GPa). An interesting option would be to coat an implant with a TiNb thin film having adequate composition and thickness so that the coating would enhance the material biocompatibility. In this work, TiNb coatings were deposited on AISI 316L stainless steel and silicon substrates by magnetron sputtering and then were characterized by scanning and transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) coupled with automatic crystal orientation mapping (ACOM). The results show that films form a homogenous solid solution and that the growth modes are not modified by the Nb content and substrate material. Also, the texture changes together with the grain growth morphology with the increase in the niobium content. For a columnar structure characteristic of zone II of the zone structure diagram (SZD) there are strongly marked textures in {113} for the x-axis, {110} for the y-axis, and {111} for the z axis. These are suppressed when the growth type changes for the T zone with the variation in the alloying element content, and that could be due to the high mobility generated during the deposition process.

Adhesion and mechanical properties of Ti films deposited by DC magnetron sputtering

Titanium films were deposited on AISI 316L stainless steel substrates by D.C. unbalanced magnetron sputtering, the substrate temperature and deposition time were changed. In this study, the structural characterization was conducted by scanning electronic microscopy (SEM), spectroscopic ellipsometry (SE), X-ray diffraction (XRD) and atomic force microscopy (AFM). Furthermore, mechanical properties were obtained by nanoindentation. Adhesion and wear behavior were evaluated through progressive load scratch test (PLST) and pin-on-disk test, respectively. Titanium films thicknesses within a range of 2.5–4.2μm were obtained, different XRD Ti peaks such as (002), (102) and (103) were identified. Values estimated for hardness were between 7.2 and 8.4GPa, and for Young's modulus they were 126–162GPa. Tensile cracks, compressive and gross spallation failure mechanisms were found with scratch tests. Preferred oriented sample only showed cracks, with a critical load of 2.6N, and exhibited a better wear ratio (~1.5×10−4), which is about two times better than substrate steel. This study provides evidence of how a preferred oriented Ti (002) film exhibits better hardness, adhesion and wear properties.

Raman Spectroscopy for Reliability Assessment of Multilayered AlCrN Coating in Tribo-Corrosive Conditions

In this study, a multilayered AlCrN coating has been employed as a protective layer for steel used in tribo-corrosive conditions. The coating was deposited by a lateral rotating cathode arc PVD technology on a AISI 316L stainless steel substrate. A ratio of Al/(Al + Cr) was varied from 0.5 up to 0.6 in the AlCrN layer located above Cr adhesion and gradient CrN interlayers. A Raman spectroscopy and potentiodynamic polarization scan were used to determine the resistance in tribo-corrosive (3.5 wt % NaCl) conditions. Correlation between sliding contact surface chemistry and measured tribological properties of material was supported with static corrosion experiments. The corrosion mechanisms responsible for surface degradation are reported.

Enhancing the barrier properties of a fluorocarbon plasma-deposited coating by producing an Interface of amorphous oxide layer on 316L stainless steel for stent applications

An amorphous nano-thick oxide layer was produced by plasma oxidation on a AISI 316L stainless steel substrate to increase the adhesion and stability of a fluorocarbon plasma-deposited coating for biomedical applications. This oxide layer decreased the corrosion rate >10-fold compared with a previous plasma-etched interface. The high corrosion resistance of the oxide layer as a new interface for fluorocarbon plasma-deposited coatings showed significant adhesion improvement by decreasing blisters formation, which are formed due to substrate corrosion. After aging in an aqueous saline solution, defluorination of the coating was less which evidenced that the fluorocarbon coating was more stable on the new interface compared with the plasma-etched interface. The coating on the new interface decreased the corrosion rate >20-fold in deformed samples compared with uncoated deformed samples. Moreover, the fluorocarbon coatings withstood a 25% plastic deformation and also a two-week aging in an aqueous saline solution. The results revealed remarkable properties of the amorphous oxide layer as a new interface on the adhesion and stability enhancement of the fluorocarbon coating to the SS316L substrate in an aqueous saline solution.

Effect of deposition parameters on structural, mechanical and electrochemical properties in Ti/TiN thin films on AISI 316L substrates produced by r. f. magnetron sputtering

Synthesis of Ti/TiN hard coatings on different substrates has been the subject of several researchers in the last decades; however, a more compressive perspective is required for the investigation of the influence of deposition parameters depending on the substrate. This paper focus on evaluating tribological and electrochemical properties of Ti/TiN bilayered coatings deposited by r.f. magnetron sputtering on AISI 316L stainless steel substrates in 3.5 wt% NaCl solutions. Numerous factors can influence the electrochemical performance and tribological properties of the coatings; for this reason, the surface modifications through thickness, texturing and morphology were realized varying the sputtering parameters (substrate temperature, T, Power, P, target-to-substrate distance t-s, and Ar/N2 gas ratio). Ti/TiN films were composed of Ti, N, which are correlated with to Ti-N, Ti-O-N and O-Ti-O phases. The friction coefficient varies from 0.12 to 1.3 by the influence of the deposition parameters; the adhesion strength shows a cohesive failure indicating that in all samples coating adhesion to steel was high enough. The corrosion resistance of Ti/TiN bilayered coatings was correlated to both the Ti/TiN film densification and formation of O-Ti-O compounds.