Steel AISI Research Articles

Comparison of test methods for crevice corrosion propagation and repassivation potential of stainless steel AISI 316

The crevice corrosion propagation modes and repassivation potential of stainless steel AISI 316 in chloride solution were compared using cyclic potentiodynamic polarization (CPP), potentiodynamic-galvanostatic-potentiodynamic (PD-GS-PD) and Tsujikawa– Hisamatsu electrochemical (THE) methods. The PD-GS-PD method was found to be the most conservative electrochemical technique which delivered the lowest repassivation potential value in a relatively short time. The crevice corrosion propagation modes in these three electrochemical methods were also compared with crevice corrosion propagation mode in galvanically coupled small area stainless steel AISI 316 anode with large area titanium cathode. The crevice corrosion propagation mode achieved in galvanically coupled AISI 316 anode at open circuit potential simulated the crevice corrosion propagation mode in real systems. The crevice corrosion propagation modes achieved in PD-GS-PD and THE methods mimicked the crevice corrosion propagation in real systems.

Analyzing microstructural, residual stress, and mechanical characteristics in dissimilar welds of Inconel 59 and AISI 904L through double-pulsed gas metal arc welding

In this research, dissimilar welding of the nickel-based superalloy Inconel 59 and austenitic stainless steel AISI 904L steel was successfully done with double-pulsed gas metal arc welding (DP-GMAW) using the filler ERNiCrMo-13. Macroscopic analysis showed a defect-free weld with an aspect ratio of 2.4, attributed to the efficient heat delivery (0.642 kJ/mm) in DP-GMAW. The microstructure of the weld joint was examined through both optical microscopy and scanning electron microscopy. Examination of the microstructure of the weld interface exposed grain coarsening near the heat-affected zone on the AISI 904L side. In contrast, the weld fusion zone contained fine equiaxed dendrites. Microsegregation and alloying element migration across the entire weld area were assessed through energy dispersive X-ray spectroscopy point analysis and line mapping, revealing controlled microsegregation across the region. X-ray diffraction (XRD) analysis was used to ascertain the average grain size (38.41 nm) and secondary phase composition. The XRD-cosα method was used to assess the residual stress of the weld joint, revealing tensile residual stress in the weld zone and compressive residual stress in other regions. Tensile, Charpy impact, and Vickers hardness tests were conducted in the study to evaluate the strength, toughness, and hardness of a dissimilar weld. The impact of two cryogenic treatments, namely shallow and deep, on tensile and toughness characteristics was investigated in this study. The cryogenic treatments significantly enhanced the mechanical properties of weld samples compared to their as-welded condition, leading to an 11.5% increase in tensile strength and a 10% improvement in toughness.

Comparative study of two retrograde locked intramedullary nail designs for ankle arthrodesis: A finite element analysis.

Ankle arthrodesis is the gold standard for treatment of end-stage arthritis. The goal of ankle arthrodesis is to obtain bony union between the tibia and the talus. Retrograde intramedullary nailing is typically reserved for ankle and subtalar joints arthrodesis. The purpose of this study is to evaluate the effect of two different materials, two locking pin configurations and two nail designs of a retrograde locked intramedullary nail used for ankle arthrodesis. Using the finite element analysis, a numerical study of ankle arthrodesis was developed to evaluate the effect of materials: TI-6Al-4V and stainless steel AISI 316 LVM; two locking pin configurations: five and six pins, on two intramedullary nails: Ø10 × 180 mm and Ø11 × 200 mm. A model of a healthy foot was created from tomographic scans. It was found that the mechanical stimulus required to achieve bone fusion were higher for Ø10 × 180 nails (6.868 ± 0.047) than the Ø11 × 200 nails (5.918 ± 0.047; p < 0.001; mean ± SEM). We also found that six-pin configuration had a higher mechanical stimulus (6.470 ± 0.047) than the five-pin configuration (6.316 ± 0.046; p = 0.020). Similarly, it was higher for titanium (6.802 ± 0.047) than those for stainless steel (5.984 ± 0.046; p < 0.001). Finally, the subtalar zone presented higher values (7.132 ± 0.043) than the tibiotalar zone (5.653 ± 0.050; p < 0.001). The highest mechanical stimulus around the vicinity of tibiotalar and subtalar joint was obtained by Ø10 × 180 nails, made of titanium alloy, with 6P.

Influences of laser remelting on mechanical performances of AISI4140 steel

Laser remelting is a promising in-operando method to improve surface quality and eliminate defects simultaneously in the laser-powder bed fusion process. In this study, the optimal processing parameters for laser remelting and the influences of laser remelting on porosity, microcracks, surface roughness, microhardness and mechanical properties of the AISI 4140 steel manufactured by laser-powder bed fusion were investigated. The results showed that laser remelting improved the relative density to 99.6% and defects in the microstructure changed from lack of fusion to keyhole morphology as the number of remelting steps increased. The roughness on the upper surface was reduced by 73% after remelting, but the roughness on the lateral surfaces deteriorated by 4.5% when remelting twice. Specimens built in the transverse orientation and treated with a single remelting step exhibit the highest tensile strength (1277 MPa). Furthermore, there is a slight improvement in the fatigue limit after remelting once. However, laser remelting in the manufacturing process did not eliminate microcracks.

Improved wear resistance of AISI-4340 steel by Ti–Nb–C–N and MoS2 composite coating by cathodic cage plasma deposition

A cathodic cage plasma deposition (CCPD) system was used to deposit titanium-niobium-carbon-nitrogen (Ti–Nb–C–N) and molybdenum-disulfide (MoS2) composite coating with a modification in the lid of the cathodic cage by inserting composite material rings in the holes. For this purpose, the combination of mixed material rings made up of (80 % TiO2+10 % graphite and 10 % Nb2O5) and 100 % MoS2 were uniformly inserted into the cage lid holes. The nano-hardness of untreated steel (2.7 GPa) was upgraded to 9.3, 11, and 12.4 GPa by composite coating at 300, 350, and 400 °C, respectively. The coating comprised TiN, Ti2N, NbN, NbC, and MoS2 phases, irrespective of the processing temperature. The thickness of the composite coating was 10.5, 13.8, and 18.6 μm. The wear volume (245 × 10−6 mm3) was reduced significantly in each condition, specifically at 400 °C temperature (∼0.1 × 10−6 mm3). The friction coefficient was smoother and lower by coating deposition, whereas the machining temperature during the wear test was reduced. The novelty of this work is that besides improving hardness, wear resistance is also improved due to the self-lubrication performance of the composite coating. In addition, the coating deposition by this system is a single-step process; less treatment time is required, and treatment is relatively low-cost.

Effect of salt bath nitriding on tribological properties of AISI52100 steel coatings using RSM

This investigation employs the salt bath nitriding to extend the service life and improve the surface characteristics of AISI 52100, commonly employed in bearing applications. A wear test was conducted using a pin-on-disc device according to ASTM G-99 standard, and the findings show a 30% reduction in wear loss. Sliding wear experiments were conducted at 1.5 meters per sec with a 5 N force at room temperature on uncoated and nitrided pins which was obtained as optimum value from RSM. The three variables five levels central composite design (CCD) were utilized in order to reduce the number of trails and the model relations were examined through ANOVA. Surface hardness, friction coefficient, wear coefficient, Loss in wear is measured over pins without coating and nitride pins. Investigations were done into how 5W30 oil affected passive and drip lubrication. Nitride substrates had a hardness of 590 HV. Also, nitriding has a favorable effect on the friction coefficient, lowering it by up to 23%. The 5W30 lubricant will further decrease the friction coefficient. The lowest coefficient of friction was seen with the addition of 14% drip oil lubrication. Significantly less wear loss in the pin was caused by a combination of high hardness and low coefficient of friction.

Fatigue life analysis of deep rolled bearing inner rings

The deep rolling process can influence the surface and subsurface of hardened steels, such as the bearing steel AISI 52100, due to mechanical loading and elastoplastic deformation. By intentionally adjusting the surface and subsurface properties, the fatigue life of bearing inner rings can be increased. This is among others attributed to the strengthening of surface and subsurface. Residual stresses induced by deep rolling and modifications of the material microstructure also contribute to this effect. In the investigations presented the deep rolling process parameters of rolling pressure, overlap ratio, and ball diameter were specifically selected based on previous works. Fatigue life investigations were conducted on honed and deep rolled bearing inner rings to enhance the understanding of failure mechanisms and to quantify the influence of the deep rolling process on fatigue life. It was found that the deep rolled bearing inner rings exhibit higher compressive residual stresses in the subsurface than honed rings and also showed longer fatigue life under rolling loads. Optical analyses of bearing rings that failed due to fatigue were performed to detect the failure mechanisms. The tested bearings showed classical fatigue, where cracking is initiated below the surface and propagates to the surface under further stress. Residual stresses can influence both the crack initiation and propagation.

Process window development of DED-LB/M process with coaxial wire for stainless steel AISI 316L

Process window development of DED-LB/M process with coaxial wire for stainless steel AISI 316L

Springback Analysis in the Bending Process of V-shaped Stainless Steel AISI 304 Using Central Composite Design (CCD) Approach

This study's principal goal is to investigate how the punch angle and punch radius impact the optimum springback during stainless steel sheet made of AISI 304 bent. Central Composite Designs (CCD) are employed for experimental design and statistical evaluation to determine the optimal springback. The experimental factors include punch angle (85,0°, 87,5°, 90,0°), punch radius (1,0 mm, 1,5 mm, 2,0 mm) with a constant 3200 Newton bending force. The analysis of variance (ANOVA) yields a substantial mathematical model that is quadratic for predicting the optimal springback. The attainment of optimal springback is foreseen through an ideal bending procedure employing a punch characterized by a 1,2 mm radius and an 89,7° angle, resulting in an anticipated average springback of 0,29°. Hence, the combination of punch angle and punch radius is pivotal in attaining the intended bending angle.

Process window development of DED-LB/M process with coaxial wire for stainless steel AISI 316L

Process window development of DED-LB/M process with coaxial wire for stainless steel AISI 316L

Experimental Investigation on the Surface Integrity in Micromilling AISI H11 Tool Steel

The surface integrity of machined components affects their fatigue performance and service life. Thus, with a view to sustainability and resource efficiency, aspects that influence the nature of the workpiece surface and sub-surface are increasingly considered in the process design, such as the resulting microhardness or the residual stress state. In this context, micromilling offers the possibility to positively influence the sub-surface properties due to the low thermal impact as well as concentrated mechanical load during machining. In order to gain a deeper understanding of the potential of micromilling for surface conditioning, experimental investigations were carried out on samples of the hot work tool steel AISI H11 in hardened condition. Cutting forces and surface topography were measured at different feed per tooth. The depth-dependent microhardness and residual stresses were determined after machining and analyzed taking into account the engagement situation and cutting forces. As the results show, micromilling can induce high compressive residual stresses as well as increase surficial microhardness while achieving low roughness topographies. This represents a great potential for improving component properties regarding tribological performance as well as fatigue behavior.

APPLICATION OF A NON-SELF-SUSTAINED GLOW DISCHARGE INITIATED BY A FOCUSED ELECTRON BEAM IN THE FOREVACUUM PRESSURE REGION FOR NITRIDING THE INNER SURFACE OF NARROW METAL TUBES

We have explored some of the features of ion-plasma nitriding the inner surface of narrow extended metal tubes by the plasma of a non-self-sustained glow discharge initiated by a focused electron beam in the forevacuum pressure range. The influence of electron beam current on the discharge parameters was determined. We found a non-monotonic dependence of plasma density, nitrogen content in the nitrided surface layer, and layer microhardness on discharge burning voltage. The microhardness of the inner surface of the nitrided tubes reaches values of 1500 kgf/mm&lt;sup&gt;2&lt;/sup&gt; for AISI 321 stainless steel and 700 kgf/mm&lt;sup&gt;2&lt;/sup&gt; for alloy carbon steel AISI 5135.

Numerical analysis of maximum force in deep drawing processes of prismatic parts

The high competitiveness of the industrial sector and the short time for developing new products drives the use of process analysis tools that enable speeding up the design phase. In sheet metal stamping projects, numerical simulation has become indispensable. As a replacement for traditional trial-and-error methods, the finite element method (FEM) enables the optimization of process-related variables. Consequently, it is possible to mitigate some of its main problems, such as the emergence of fracture, wrinkling, and springback. A second alternative for analyzing the process, even faster and cheaper, is based on the use of analytical calculations. These can predict, among other parameters, the forces involved in stamping. This study aims to evaluate the degree of accuracy of equations predicted in the literature to estimate the maximum stamping force of non-axisymmetric parts. For this purpose, analytical results of the stamping force of 1 mm thick austenitic stainless steel AISI 304 sheets were compared to results obtained via numerical simulation.

CORROSION RESISTANCE OF COLD-ROLLED AISI 301 STAINLESS STEEL

: The performed investigations concerned on the effect of cold rolling on the corrosion behavior and microstructure of austenitic AISI 301 stainless steel. Samples of steel strip were cold-rolled within the degree of deformation 30%, 50% and 80%. The corrosion resistance test was examined using gravimetric and potentiodynamic method. Corrosion tests were conducted in acidic and alkaline corrosive environments. A light microscope and a scanning electron microscope were used to observe the surface morphology of the samples after corrosion testing. Corrosion tests by gravimetric method showed that investigated steel is not resistant to corrosion in 0.5N H2SO4 solution, while no significant weight loss was observed in artificial seawater solution (0.5N NaCl). Based on potentiodynamic tests carried out in 0.5N NaCl solution, it was found that the pitting corrosion resistance of the tested cold-rolled steel AISI 301 decreases with an increase in the degree of plastic deformation in the range of 30% to 80%. However, a decrease in the corrosion potential and an increase in the current density were observed on the polarisation curves. The propensity of the steel to initiation and propagation pitting was found to increase both with increasing degree of deformation and the associated increase in the volume proportion of martensite- in the material structure. The occurring of martensite- ’ in the investigated steel was confirmed by X-ray methods.

Hard-soft biomimetic structure distribution enhanced wear resistance of AISI1045 steel by laser processing

In this study, the biomimetic unit samples (BUSs) of hard-soft structure with different distribution spacings were successfully prepared by laser quenching biomimetic processing technique (LQBPT). Firstly, the microstructure, microhardness, tribological properties and wear surfaces were investigated. The BUSs had randomly oriented martensite and M7C3, and the grains were refined, resulting in favorable hard-soft structures. Compared to the untreated samples, the BUS at distribution spacing of 3 mm had excellent wear resistance. Its average friction coefficient and weight loss were reduced by 17.95 % and 40.0 %, respectively. Then, it was investigated the quantitative relationship between the distribution spacing and the wear resistance and its wear resistance mechanism. This improved wear resistance was attributed to hard-soft biomimetic structure.

Mechanical Properties of Indentation in Plasma Nitrided and Nitrocarburized Austenitic Stainless Steel AISI 321

Austenitic stainless steels are widely used due to their resistance to corrosion and to the possibility of using them at temperatures above 600 °C. Plasma nitriding and nitrocarburizing consist of a thermochemical process that introduces nitrogen and nitrogen/carbon, in atomic form, allowing the formation of second phases of these elements with the substrate. These thermochemical treatments of plasma nitriding and nitrocarburizing were performed on austenitic stainless steel AISI 312 at temperatures of 400 °C and 500 °C, obtaining thicknesses of around 12 μm and 24 μm, respectively. Mechanical properties of indentation were obtained using a Hit 300 nanoindenter (Anton Paar), in a load-unload cycle and with a depth of up to 10% of the layer, with Berkovich indenter. The elastic moduli obtained for the nitrided layers were 281 ± 21 GPa (400 °C) and 163 ± 32 GPa (500 °C) and for the nitrocarburized were 214 ± 12 GPa (400 °C) and 169 ± 25 GPa (500 °C). The indentation nanohardness obtained for the nitrided layers were 14.1 ± 1.0 GPa (400 °C) and 3.5 ± 1.2 GPa (500 °C) and for the nitrocarburized layers were 10.8 ± 0.8 GPa (400 °C) and 4.3 ± 1.2 GPa (500 °C). Therefore, these results indicate slightly higher values for the two mechanical properties indentation (elastic modulus and nanohardness) at 400 °C than at 500 °C caused by nitriding compared to nitrocarburizing treatment; however, when considering the percentages of standard deviations, the treatments at 500 °C present much higher values for these properties, as compared to the treatments at 400 °C, a behavior associated with the presence of chromium and iron nitrides.

Effect of ultrasonic shot peening and intermediate cerium salt conversion bath treatment controlling corrosion of Mg-Y-Zn-based alloy in salt water

Ultrasonic shot peening (USP) is often regarded as beneficial in mitigating corrosion of Mg alloys. However, increasing surface roughness induced by USP promotes localized corrosion pitting. Herein, we show that an intermediate phosphate bath treatment (CePT) before USP can minimize the surface roughness and ameliorate corrosion resistance of Mg-4.0Y-4.0Zn-0.5Zr-0.2Ca alloy (wt.%) in 0.1 M NaClsolution. In this regard, WZ44 alloy was subjected to Ce(NO3)3 + NaH2PO4bath treatment followed by USP for 30 s using AISI52100 steel balls and vice versa. The sub-surface features ofspecimens analyzed using XRD, FESEM, surface topography, and Vickers hardness reveal that CePT coating before USP increases microhardness (∼142–149 HV0.05 vs ∼ 125–135 HV0.05) and decreases surface roughness (Ra = 1.91–2.38 μm vs Ra = 2.58–2.76 μm). Potentiodynamic polarizationand electrochemical impedance spectroscopy demonstrate that corrosion current decreased (Icorr ∼ 9.81–13.69 µA/cm2 vs. ∼ 23.82–26.22 µA/cm2), coating (R1), and polarization resistance (R2) increased to ∼ 1704–1907 Ω.cm2,and ∼ 1834–1902 Ω.cm2, respectively,for specimens subjected to USP + CePT treatment together indicating superior corrosion resistance.Overall, an intermediate CePT before USP can effectively minimize corrosion pitting phenomena of WZ44 alloy in chlorinated solution by developing a ceramic coating interlocked with surface acting as a barrier between the metal/solution interface.

Prospects for the Use of Metal Surfaces Modified by Nanosecond Laser Radiation for Energy Applications

Laser technologies for processing metals used as heat exchange surfaces are unrivaled to solve a number of problems in the energy industry. This is explained by the fact that after laser radiation treatment, metal surfaces gain unique surface functional properties (extreme wettability properties, high resistance to corrosion in contact with traditional coolants, high abrasive and cavitation resistance). The study of the processes of evaporation, boiling, and condensation on such surfaces is hampered by one of the unsolved problems, which is the lack of the ability to predict the configuration of microtextures, for example, in the form of micropillars and microchannels with predetermined sizes. In this work, a graphic–analytical technique based on the use of ablation spot sizes for the formation of a given configuration and microtexture dimensions on traditional structural materials of heat exchange surfaces is developed. Based on experimental data, regime maps were constructed for the formation of microtextures on the surfaces of aluminum alloy AlMg6 and steel AISI 310. The prospects for using metal surfaces with a given microtexture formed by laser radiation to intensify the phase transition of coolants and control convective flows in a droplet lying on a heated surface were assessed. The obtained results can be used in the development of spray (drip) irrigation systems to provide thermal protection for heat-stressed equipment.

Optimisation of laser welding parameters to maximise the joint strength of laser weld stainless steel joints using a GA for geothermal plants

ABSTRACTLaser beam welding is vital in high-temperature fields such as the aerospace, automobile, and gas turbine manufacturing industries. In this article, parametric studies are carried out on Nd:YAG laser weldments that influence stainless steel 430 L weldment quality. A series of trial runs are organised to investigate input parameters such as peak power, frequency, speed, and time that impact output responses such as yield strength, ultimate tensile strength, shear strength, and elongation simultaneously. Trail runs on martensitic stainless steel AISI 430 L are conducted based on Taguchi experiments, and a regression equation is established. To yield optimum results, the process parameters are optimised by using the genetic algorithm optimisation technique. By conducting experimentation with optimum parameters, the output responses are compared with the optimum results 95% confidence level was obtained. The optimum levels for process variables are identified for quality weld peak power 160 kW, frequency 9 Hz, speed 3.33 mm/ms, and time 2.53 ms. Optical microscopy reveals that refined grains are formed in the weld zone with a grain size of 2.909 µm, and a scanning electron microscopy test is performed to study the morphology of AISI 430 L weldment specimen failure takes place at the interface of the weld metal.

Water droplet erosion assessment in the initial stages on AISI 316 L using kernel average misorientation

Surfaces exposed to natural forces in the form of water droplets are structurally deformed over time through changes in their surface morphology. Plastic deformation in thin subsurface layers where compressive stress prevails is typical for this stage of erosion. The stress accumulation does not exceed the fatigue limit, so the structural integrity is not broken. Information about this stage has been obtained by post-experimental assessments using various observation techniques. This article considers the changes to a surface using techniques to assess a specific site before and after exposure to the erosive action of water droplets. An electron backscatter diffraction analysis was conducted pre-exposure of water droplets for detection on an electrochemically polished surface of stainless steel AISI 316 L. Specific areas that were exposed to the effects of water droplets at subsonic speed were marked with indents. The droplets were generated by an ultrasonic pulsating water jet (PWJ) with a nominal frequency of 40 kHz and supply pressure of p = 50 MPa. To assess the development in the very early stages of erosion, individual runs were performed with a time range of 1–3 s. The erosion development was compared with control runs, where a continuous water jet (CWJ) with a frequency of 1 Hz was used with a time range of 3–6 s. A post-exposure electron backscatter diffraction analysis showed a real change in the grain orientation using kernel average misorientation. It was found that multiple droplet impingement changes the grain geometry and results in an increase in misorientation inside the grains. The misorientation distribution in the zone treated by the water jet was not homogeneous over the entire cross-section of the sample; the CWJ required double or even triple the time to achieve a similar level of plastic deformation when compared to the PWJ.