AISI 316L Steel Research Articles

Microhardness, Resistivity and Tribological Properties of Coatings Based on Hf/Hfn Bilayers Deposited By Sputtering

In this work, coatings based on hafnium/hafnium nitride (Hf/HfN) bilayers were synthesized by the magnetron sputtering technique, producing coatings with 4, 8 and 16 Hf/HfN bilayers on AISI 316L steel and silicon (100). The surface morphology was studied, which shows a high uniformity of grain cluster groupings. Their microhardness was evaluated where the hardness of the 316L steel was improved by more than 3 orders of magnitude, with a value of 6.71 GPa for 8 Hf/HfN bilayers, this same condition reached a high value of electrical resistivity of 6.55x1014 µΩ-cm, a reduction in the coefficient of friction by about 25% with respect to 316L and presented a total delamination of the coating at 19.77 N, which could allow these coatings to be canted for corrosion protection of 316L steel.

Impact of Deposition of the (TiBx/TiSiyCz) x3 Multilayer on M2 HSS on the Cutting Force Components and Temperature Generated in the Machined Area during the Milling of 316L Steel.

High-speed steel (HSS) tools account for 20 percent of the cutting tools materials’ global market. This is due to both their significant toughness and resistance to cracking, compared to cemented carbides. Covering steel tools with hard coatings clearly improves their mechanical properties, wear resistance, and significantly increases their durability. Physical vapor deposition methods are preferred for coating metal substrates, as they allow low temperature deposition. The most widely deposited coating materials are carbides, nitrides, and borides. They are combined with softer ones in the multilayer structure to promote increased resistance to cracking and delamination in comparison to monolayered structures. In this paper, the M2 steel end mills were coated by (TiBx/TiSiyCz) x3 multilayer by the pulsed laser deposition method. Coated and uncoated tools were tested in the cylindrical down milling of AISI 316L steel. Components of the cutting force and temperature generated in the machined area during dry milling were measured under two variants of operating conditions: V1 and V2. Tool wear mechanism was examined using scanning electron microscopy (SEM), accompanied by EDS analysis of worn areas. It was found that milling with higher speed (variant V2) is accompanied by lower cutting force components and a lower temperature generated in cutting area. The presence of the coating allowed lower cutting forces and temperature in the case of variant V1. The temperature measured during milling did not exceed 200 °C. The SEM observation of the edges of cutting tools indicated that the main mechanism of wear for both types of tools was abrasion. The built-up edge formation was observed in the case of tools tested at the V1 cutting parameters variant. It was assumed that it was the reason for higher cutting forces measured during milling according to this variant. The chemical composition of built-up edges was different for coated and uncoated tools. Tribo-chemical reactions were responsible for the reduction of the cutting force and temperature components observed during milling with a coated tool at V1 variant. Boron and titanium were the elements of the coating that enabled the tribo-oxidation reactions thanks to which friction was reduced. Our results show that this beneficial effect occurs with (TiBx/TiSiyCz) x3 coated tools, but can easily be lost with inadequately selected cutting parameters.

Measurements of Liquid AISI 304L Steel Density and Surface Tension, and Influence of Surface‐Active Elements at High Temperatures

Within the framework of the welding of steel components in pressurized water reactors, the optimization of the weld pool penetration is a major issue. The thermal‐hydraulics of the molten steel pool can be driven by Marangoni flows at the free surface. To compute these flows, liquid steel's thermophysical properties such as density ρ and surface tension σ are required. Such properties for austenitic vessel steel AISI 304L at liquid state are scarce, and even not available above 1800 °C, due to technological issues. The viscometer temperature installation (VITI) is designed to implement sessile droplet (SD) and maximum bubble pressure (MBP) techniques. These techniques allow to determine original ρ and σ data for two grades of AISI 304L steel, namely 304LP1 and 304LP4—low and high sulfur content, at various temperatures. In particular, thanks to the innovative design of MBP configuration, original surface tension data are obtained from the melting point up to 2100 °C. For the first time, experimental evidence of the Sahoo et al.'s (1988) model at high temperature is provided, emphasizing the decisive role played by surface‐active elements such as sulfur and oxygen on surface tension, whose content evolution is assessed by dedicated chemical analyses.

The Influence of the Processing Parameters on the Laser-Ablation of Stainless Steel and Brass during the Engraving by Nanosecond Fiber Laser.

In this paper, we investigate the influence of the following parameters: pulse duration, pulse repetition rate, line-to-line and pulse-to-pulse overlaps, and scanning strategy on the ablation of AISI 316L steel and CuZn37 brass with a nanosecond, 1064-nm, Yb fiber laser. The results show that the material removal rate (MRR) increases monotonically with pulse duration up to the characteristic repetition rate (f0) where pulse energy and average power are maximal. The maximum MRR is reached at a repetition rate that is equal or slightly higher as f0. The exact value depends on the correlation between the fluence of the laser pulses and the pulse repetition rate, as well as on the material properties of the sample. The results show that shielding of the laser beam by plasma and ejected material plays an important role in reducing the MRR. The surface roughness is mainly influenced by the line-to-line and the pulse-to-pulse overlaps, where larger overlap leads to lower roughness. Process optimization indicates that while operating with laser processing parameters resulting in the highest MRR, the best ratio between the MRR and surface roughness appears at ~50% overlap of the laser pulses, regardless of the material being processed.

Decomposition kinetics of expanded austenite with high nitrogen contents

Abstract This paper addresses the decomposition kinetics of synthesized homogeneous expanded austenite formed by gaseous nitriding of stainless steel AISI 304L and AISI 316L with nitrogen contents up to 38 at.% nitrogen. Isochronal annealing experiments were carried out in both inert (N2) and reducing (H2) atmospheres. Differential thermal analysis (DTA) and thermogravimetry were applied for identification of the decomposition reactions and X-ray diffraction analysis was applied for phase analysis. CrN precipitated upon annealing; the activation energies are 187 kJ/mol and 128 kJ/mol for AISI 316L and AISI 304L, respectively. Isothermal stability plots for expanded austenite developed from AISI 304L and AISI 316 were obtained.

Improving the Corrosion Resistance of AISI 316L Steel for Semiconductor Piping by Controlled Delta-Ferrite Content

This study evaluated changes in delta-ferrite content depending on the preheating of AISI 316L stainless steel. We also determined the reasons for the variation in delta-ferrite content, which affects corrosion resistance. Changes in delta-ferrite content after preheating was confirmed using a Feritscope, and the microstructure was analyzed using optical microscopy (OM). We found that the delta-ferrite microstructure size decreased when preheating time was increased at 1295 oC, and that the delta-ferrite content could be controlled through preheating. Potentiodynamic polarization test were carried out in NaCl (0.5 M) + H2SO4 (0.5 M) solution, and it was found that higher delta-ferrite content resulted in less corrosion potential and passive potential. To determine the cause, an analysis was conducted using energy-dispersive spectroscopy (EDS), which confirmed that higher delta-ferrite content led to weaker corrosion resistance, due to Cr degradation at the delta-ferrite and austenite boundaries. The degradation of Cr on the boundaries between austenite and delta-ferrite can be explained by the difference in the diffusion coefficient of Cr in the ferrite and austenite. A scanning electron microscopy (SEM) analysis of material used for actual semiconductor piping confirmed that corrosion begins at the delta-ferrite and austenite boundaries. These results confirm the need to control delta-ferrite content in AISI 316L stainless steel used for semiconductor piping.

Optimization and measurement of kerf width and surface roughness of AISI 316L

AISI 316L steel has wide applications in production of parts used in automobile, biomedical and aviation industries. Machining of AISI316 steel for production of parts with accuracy can be achieved by WEDM. In this work machining of AISI 316L stainless steel is performed using wire electrical discharge machining (WEDM). Taguchi L27 orthogonal array is used to design of machining with five process parameters (wire feed rate, voltage, pulse on time, pulse off time, and peak current). The response parameters surface roughness (SR), and kerf width (Kw),are optimize using single point optimization tool Taguchi S/N ratio, and multi response optimization tool grey relation analysis (GRA). The values of surface roghness (minimun), and kerf width (minimun) are1.76 µm, and 0.07 mm, respectively. Minimun value of SR is observed at wire feed rate of 30 mm/s. A factor level analysis for minimum SR gives optimal response is for Wf- 1, Ip - 3, Ton - 3, voltage – 2, Toff - 3, and for Kw is Toff - 3 Ton - 1, voltage - 2, Wf - 1, Ip - 3. Multi-response optimization is performed using Grey relation analysis (GRA) to select the optimal values of response parameters. Optimum result is obtained at peak current Ip-3 A, Ton 9 µs, Toff 12 µs, voltage 60 V, and wire feed rate 30 mm/s.

Análise da Junta Soldada Dissimilar entre Inconel 718 e AISI 316L pelo Processo GTAW Multipass

Abstract: AISI 316L steel and Inconel 718 are metals of wide application in industries. The study of dissimilar welding between these two materials is technologically important to improve their joint performance. We focused this study on the evaluation of the dissimilar weldability of these materials. Three samples of AISI 316L and Inconel 718 welded using a multipass GTAW (Gas Tungsten Arc Welding) process with different parameters were analyzed. The microstructural characterization, measurements of the volumetric fraction of the δ ferrite and Laves phase, the spacing between austenite dendrites, in addition to measurement and analysis of dimensions of the welding zones and the microhardness were performed. The measurement of the weld metal dimensions and the dendrite spacing showed that higher heat inputs increased the dilution zones and the spacing between austenite dendrites. The volumetric fraction of the δ ferrite decreased with the increase of heat input, while the Laves phase fraction increased. The microhardness presented significant variation in the weld pool due to changes in the phases and composition, as evidenced by EDS analysis in the dissimilar joints.

Prediction models for the kinetics of iron boride layers on AISI 316L steel

Abstract The boronizing kinetics of AISI 316L steel has been analyzed by employing five prediction models. The boron diffusion coefficients as well as the growth rate constants in the FeB and Fe2B phases were firstly evaluated in the range of 1123-1223 K. Afterwards, the values of boron activation energies in FeB and Fe2B were secondly deduced by adopting the Arrhenius relationships.In addition, the prediction models have been validated experimentally for two boronizing conditions (1170 K for 1.6 h and 1210 K for 1.1 h). The predicted results were deemed very concordant with the experiments. Furthermore, advantages and limitations about the applicability of these models were also discussed.

Fatigue life assessment in the very high cycle regime of AISI 316L stainless steel processed by L-DED additive manufacturing

Additive manufacturing technologies have arisen great industrial interest for manufacture of components and final parts intended for applications in several sectors of the industry. Most of these components are designed to have a service life greater than 107 cycles, making the analysis of the fatigue behaviour in the very high cycle regime (VHCF) an essential design criterion. The 316L stainless steel is one of the most processed and discussed in the literature. However, there is still no consolidated knowledge about the fatigue life of this material manufactured by different available techniques and their respective mechanisms of initiation of cracks predominant in the VHCF regime. The present work is intended for an experimental study of the VHCF failure mechanism of AISI 316L steel after additive manufacturing by laser directed energy deposition. In order to also identify the effect of post-processing steps, two different conditions of the material (as built and heat treated) were analysed. The specimens were submitted to ultrasonic tests with a target number of 109 cycles, at a frequency of 20±0,5 kHz and R=-1. The fracture surfaces were analysed later and the influence of heat treatment on the population of metallurgical defects, “fish-eye” formation and material's fatigue life were verified.

A comparison on the Energy Release between traditional and Additive Manufactured AISI 316L steel during static tensile test

Additive Manufacturing (AM) allows the creation of mechanical components and biomechanical devices with low weight and reduced material consumption compared to traditional manufacturing techniques. Despite design opportunities increase, on the other hand, also the process parameters to consider when dealing with AM are relevant on the mechanical performance. It is of fundamental importance to assure the structural integrity and reliability of such components. Energy release could give relevant information on the mechanical performance of the material; hence the Static Thermographic Method (STM) has been proposed as a rapid test procedure to assess the initiation of damage within the material monitoring the temperature evolution during static tensile tests. The aim of the present work is to compare the energy release of a stainless steel during static tensile tests. Specimens made of AISI 316L were produced with the same geometry, both with traditional and AM techniques. A comparison on the microstructure has been also performed in order to assess the possible cause of failure under static loads.

Parametric analysis and simulation of surface roughness and tool flank wear in machining of low carbon alloy steel

Austenitic SS influences in most frequently applied corrosion resistance or in higher surface loading were it is required. The present investigation represents the quality attributes namely surface roughness and tool wear rate in turning of AISI 316L steel using DoE. Taguchi method has been employed with L9 (34) orthogonal array of the three significant factors, i.e., speed, feed and depth of cut, to achieve the minimum surface roughness and tool wear rate. The Analysis of variance was performed to identify the influencing factors which affect the responses. The outcomes from the research reveal that the minimum surface roughness was achieved at cutting speed 170 m/min, feed rate 0.10 mm/rev, depth of cut 0.15 mm and the minimum too wear rate was attained at 170 m/min cutting speed, 0.07 mm/rev feed rate and 0.15 mm depth of cut was determined using the experimental study and compared with the prediction model from design of experiments. The results shows that both the values were good in agreement with experimental as well as prediction results.

Effect of electroplating temperature on microstructure, corrosion, and wear behavior of Ni-P-W-TiO2 coating

Nickel-phosphorus-titanium oxide coating was fabricated on the AISI 304L steel substrate using the electroplating method. Electroplating was performed at temperatures of 55, 60 and 65 °C, and the effect of electroplating temperature on microstructure, corrosion behavior, and wear behavior was investigated. The coatings were characterized by use of scanning electron microscopy (SEM). In order to investigate corrosion resistance, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were performed in 3.5% of NaCl aqueous solution. A pin on disk test was employed to investigate the wear resistance of uncoated and coated samples. Sample micro-hardness was also measured by the Vickers hardness test. The results of potentiodynamic polarization and electrochemical impedance spectroscopy tests results showed that the coating created at temperature of 60 °C had the highest corrosion resistance (7058 Ω.cm2) compared to coated sample at temperature of 55 °C (2115 Ω.cm2) and 65 °C (2289 Ω.cm2). Also, the results of the wear and micro-hardness test showed that composite coating formed at temperature of 60 °C had the highest wear resistance and micro-hardness (677 Vickers) compared to coated sample at temperature of 55 °C (411 Vickers) and 65 °C (536 Vickers).

Evolution of corrosion products on ASTM A36 and AISI 304L steels formed in exposure to molten NaNO3–KNO3 eutectic salt: Electrochemical study

Thermal energy storage uses molten salt as a heat transfer fluid implies a high corrosion risk. In this work, ASTM A36 and AISI 304L steel, exposed to solar salt at 390 °C for 21 days, were studied by electrochemical impedance spectroscopy. The results were validated by mass gain and the characterization of corrosion products. Carbon steel revealed a porous behavior related to the formation of corrosion products based on iron oxides, as described the De Levie´s theory, whereas stainless steel showed the formation of a passive multilayer of iron and chromium oxides, which was adjusted to the Power-law model.

The properties of AISI 316L steel after surface treatment with Ti surface alloy and a-C:H:SiOx coating

The paper presents the research results of corrosion and mechanical properties of the AISI 316L stainless steel after the surface treatment. This treatment includes the formation of the titanium-based surface alloy provided by the low-energy high-current electron beam. The obtained surface alloy used as an underlayer, is then coated with the a-C:H:SiOx film using the PACVD method. It is shown that such a combined treatment of the steel surface improves its corrosion resistance, i. e., reduces the current density from 110-7 to 910-10 A/cm2 and corrosion rate from 1.110-3 to 9.310-6 mm/year. The resulted modified steel surface possesses high mechanical and tribological properties

Optimization of the Cutting Regime in the Turning of the AISI 316L Steel for Biomedical Purposes Based on the Initial Progression of Tool Wear

The development of biomedical devices has improved the quality of life for millions of people. The increase in life expectancy generates an increase in the demand for these devices. One of the most used materials for these purposes is 316 L austenitic stainless steel due to its mechanical properties and good biocompatibility. The objective of the present investigation was to identify the dependence between the main cutting force, the initial speed of the tool wear, the surface roughness, and the parameters of the cutting regime. Based on these dependencies, a multi-objective optimization model is proposed to minimize the energy consumed and initial wear rate, as well as to maximize productivity, maintaining the surface roughness values below those established by the ISO 5832-1 standard. The wear of the cutting tool was measured on a scanning electron microscope. For the optimization process, a genetic algorithm based on NSGA-II (Non-nominated Sorting Genetic Algorithm) was implemented. The input variables were the cutting speed and the feed in three levels. The cutting force and surface roughness were set as restrictions. It is concluded that the mathematical model allows for the optimization of the cutting regime during dry turning and with the use of MQL (Minimum Quantity Lubrication) with BIDEMICS JX1 ceramic tools (NTK Cutting Tools, Wixom, MI, USA), of AISI 316 L steel for biomedical purposes. Pareto sets and boundaries allow for choosing the most appropriate solution according to the specific conditions of the workshop where it is applied, minimizing the initial progression of tool wear and energy consumed, and maximizing productivity by guaranteeing the surface roughness values established for these types of parts according to the standard.

Coupled elasto-viscoplastic and damage model accounting for plastic anisotropy and damage evolution dependent on loading conditions

This work presents an unconventional fully coupled elasto-viscoplastic and damage constitutive model that is suitable for investigating the failure mechanism of metallic materials. The constitutive equations are developed within a finite elastoplasticity framework under the assumption of hypoelastic-based plasticity. Anisotropic plastic potential and plastic-induced anisotropy are modelled by means of the Hill48 yield criterion and a Chaboche-type non-linear kinematic hardening law, respectively. A modified Voce-type law is assumed for the isotropic hardening behaviour. A novel law is proposed to account for an evolution of the damage depending on the loading directions. The proposed model was implemented via user subroutine for the commercial finite elements (FE) software Abaqus/Standard and used for the prediction of the cyclic failure of lead-free solder materials, the crack formation in anisotropic AISI 316L steel specimens and the description of the failure behaviour of carbon steel notched round bars and flat grooved plates.

Experimental Investigation and Numerical Prediction of the Effects of Cutting Tool Geometry During Turning of AISI 316L Steel

In this work, a numerical and an experimental study aimed to gain a better understanding of the impact of tool geometry such as (rake angle and cutting edge radius) on the temperature distribution and residual stresses in machining surface of AISI 316L stainless steel have been presented. To evaluate the experimental results, various experimental equipment was used, such as a conventional lathe to carry out the machining operations, the cutting force was measured using a Kistler dynamometer and X-ray diffraction technique was employed for determination of the residual stresses distribution on the machined surfaces. In addition, A thermo-mechanically coupled finite element (FE) analysis for cutting process is developed through ABAQUS code to predict the temperature distribution and residual stresses using an Arbitrary Lagrangian-Eulerian (ALE) approach. An inverse identification method has been used to determine the adequate Johnson-Cook (JC) material model parameters to obtain a good correlation between the cutting force measurements and numerical one. The FE model was then validated by comparison of the numerical results of residual stresses with experimental measurements for different tool geometries, which revealed a reasonable agreement.

Technological features of growing a combustion chamber of a liquid-propellant rocket engine by method of selective laser melting from AISI 316L steel

ABSTRACT This work is devoted to the applied possibilities of the selective laser melting technology in the rocket industry. The properties of stainless steel formed by volumetric growth at various modes are investigated; the influence of the laser main parameters of laser treatment on the properties of the material is traced. The formation of the smallest possible size of the structures of the cooling path of LRE has been worked out. As a result of the performed work, a model of the liquid rocket engine (LRE) cooling path with a developed heat exchanger surface was manufactured and tested.

Modelling of Stainless Steel AISI 316L in Finite Element Simulations

AbstractThis paper addresses numerical modelling of a rolled, austenitic stainless steel of grade AISI 316L, corresponding to EN 1.4404. The study comprises uniaxial tension tests at a range of temperatures (from –20°C to 200°C) and at two different strain rates (10–3 s–1 and 10–1 s–1). It appears that the material is very ductile and hardens significantly. The strength and hardening depend on temperature, while the strain‐rate effect is minor. The results from the tension tests are used to calibrate two different material models. The first one is a fully parametrized elasto‐viscoplastic model of Johnson‐Cook type, incorporating temperature and strain rate as variables, and including the one‐parameter Cockcroft‐Latham failure criterion. The other model is defined through direct input of the true stress‐strain curve at a given temperature and rate. This model does not incorporate failure. In the validation part of the study, the models are employed in numerical simulations of plane‐strain tension tests on notched specimens. It appears that both models capture the main features of the tests.