AISI Type Research Articles

Analysis of the Effect of Turbine Operational Load on the Strength of Coupling Bolt Structure Using the Finite Element Method

In transmitting kinetic energy from the turbine to the generator, the coupling will experience stress and deformation, especially on the bolts that support the coupling. Therefore, it is important to analyze how the operational load of the turbine affects the strength of its bolt structure. The author has conducted a literature study and numerical simulation to analyze the problem. In the simulation that has been done, it was found that the maximum von misses stress and strain values received by the bolt were 196.34 MPa and 0.0009687 mm/mm at maximum loading. The relationship between operational load and von misses stress value is that if the operational load is higher, the von misses stress received by the bolt will also be higher. Furthermore, there is also a relationship between operational load and von misses strain value, namely that if the operational load is higher, the von misses strain received by the bolt will also be higher. DBy using AISI Type S5 Tool Steel – Oil Quenched to 55 HRC, a relationship was obtained between operational load and safety factor value. The relationship between operational load and safety factor value is that if the operational load is higher, the safety factor value will be lower. From the simulation that the author has done, it is found that there is a difference in safety factor if the material used in the bolt is changed. It was found that AISI Type S5 Tool steel - Oil Quenched to 55 HRC has a higher safety factor value of 8.8111.Meanwhile, the AISI Type S5 Tool Steel material, Austenitized 855 – 870°C (1575 – 1600°F), Oil Quenched to 45 HRC has a lower safety factor value, namely 5.7552.

Improvement of intergranular corrosion resistance of SS 304L by grain refinement followed by gamma-ray irradiation treatment for the application in the back end of the nuclear fuel cycle

The severe plastic deformation (SPD) technique has been widely used for grain refinement to produce bulk ultra fine-grained (UFG) microstructure. In this study, an improved corrosion-resistant material of type 304L stainless steel (SS) has been designed, from the coarse-grain (CG) microstructure to the UFG microstructure using the SPD technique through cryo-rolling at liquid nitrogen (at 77K) temperature followed by gamma-ray irradiation treatment. In comparison to the effect of gamma-ray on both CG and UFG microstructure, both specimens were irradiated with an equal amount of doses. Gamma (γ) ray irradiation (dose rate: 2.83 kGy/h) affected the corrosion resistance of AISI type 304L stainless steel (in both CG and UFG) in concentrated nitric acid (65 wt%) medium. The correlation of irradiation effects on the microstructure and nitric acid corrosion behaviors has been discussed, which is important for designing materials for application in nuclear-spent fuel reprocessing plants.

Tensile Effect on Sensitization and Corrosion Resistance of Stainless Steels

The purpose of this research is to investigate cold work effect on corrosion behavior of stainless steels of type AISI 304, AISI 316L and AISI 2101. The specimen were processed through cold work simulated by the tensile test at various percentages elongation and then tempered at 600°C for different time intervals. Two electrochemical techniques and hardness test were utilized in this investigation. The first technique was the double loop electrochemical potentiokinetic reactivation (DL-EPR) that yields the values of degrees of sensitization (DOS). The second one was the cyclic potentiodynamic polarization (CPP) to study the ability of the metals to build or repair the damaged films under localized corrosion. The DOS values from the DL-EPR tests of the samples under the same heating conditions suggested that specimens drawn at higher percentage elongation tend to have more chromium depleted areas. Also, the test specimens with more exposure time to heat were more prone to chromium deficiencies. As for the ability of the metal to create or repair damaged film after corrosion has occurred, it was found that AISI 316L had hihger corrosion resistance than AISI 304. However, AISI 2101 stainless steel had highest corrosion resistance. In this study, it was also found that AISI 2101 did not exhibit pitting corrosion, but the crevice corrosion. This could be due the fact that AISI 2101 which is a duplex stainless steel has high corrosion resistance and could trigger the crevice corrosion take place before the pitting initiation.

Stainless steel as an electrocatalyst for overall water splitting under alkaline and neutral conditions

The development process for an effective catalyst for electrochemical water splitting must consider properties such as chemical and mechanical stability, corrosion resistance, and abundance alongside efficiency. In this work, a detailed electrochemical evaluation of four types of commercially available AISI stainless steel (302, 304, 316, and 321) was performed for their electrocatalytic activity, stability, and corrosion resistance in overall water splitting under alkaline (pH 14.00) and near-neutral conditions (pH 6.26). Using AISI plates directly as an anode or cathode, a current density of 10 mA cm−2 was obtained at η ≈ 0.38 V for OER and η ≈ 0.43 V for HER in 1 M KOH. Although all of the tested types have proved to be efficient electrocatalysts, detailed electrochemical studies have distinguished certain differences between the AISI types, depending mainly on the composition peculiarities. A detailed corrosion evaluation has revealed that although all measured stainless steels are sensitive to the oxidative environment, their corrosion rate does not exceed 3.3 µm per year.

Experimental investigation into the effect of magnetorheological fluid damper on vibration and chatter in straight turning process

Magneto-Rheological (MR) dampers have received a great deal of attention in recent years due to the potential of offering semi-active control. MR dampers have been successfully applied in the vibration control of several machining processes. However, the effect of the material of the damper's fluid chamber on its magnetic properties has not been studied much. In this study, an MR damper has been designed to control the chatter vibration of the straight turning operation. The magnetic properties of the MR damper are simulated in the FEM software COMSOL Multiphysics with two types of steel AISI 410 and AISI 1018, and the material with the best performance for constructing the fluid chamber is determined. Then, the MR damper with an assembly to hold the cutting tool was fabricated and experimentally tested during straight turning operation and its effect on the tool vibration, and work surface roughness was analyzed. From the result, it was observed that the MR damper reduced tool vibration and chatter effectively. The results obtained in this research confirm that the application of the MR damper in the straight-turning process can either suppress the chatter or greatly reduce the frequency amplitude of the chatter. The reduction of the tool's acceleration amplitude with the MR damper was more intense in the condition of chatter suppression and reached up to 89.42 %. Moreover, the MR damper reduced the roughness of the machining surface. This reduction was higher in cases where the chatter was suppressed and it was observed up to 29 %.

Investigating the effects of double-pass TIG welding on the mechanical and microstructural properties of AISI 1008 steel

ABSTRACT Most premature failures of double-pass weldments are associated with limited knowledge of the mechanical and microstructural evolution following the welding process. Thus, this study aims to investigate the effect of double-pass tungsten inert gas welding on the mechanical and microstructural properties of type AISI 1008 mild steel joints. Double-pass TIG welding in butt joint configuration was adopted to weld the plates maintaining a 2.5 mm root gap in between plates. The double-pass tungsten inert gas welded AISI 1008 joints showed improved ultimate tensile strengths in contrast to the unwelded counterpart, with the least joint efficiency of 82.67 % (weld W3). An increase in the heat input led to a corresponding increase in the weld metal hardness, whereas the hardness of the heat-affected zones increased first and then decreased. The internal geometry of the welds reveals an increase in the bead width, height of reinforcement, width of the heat-affected zone, and weld metal area as the heat input increases. Lastly, the microstructural evolutions of the weld metal zones were primarily dominated by widmanstatten ferrite, acicular ferrite, and pearlite structures, accounting for the enhanced tensile strength and hardness of the joints. Meanwhile, the heat-affected zones were characterised by coarse columnar dendrite structures resulting in lower hardness values. This study gives an insight into the mechanical and microstructural properties of the industry’s most frequently used steel grade, which has not been given much attention in past studies. The research finding enriches the welding theory of A1SI 1008 steel for industrial and academic benefits.

열교환기용 스테인레스강 열화 용접부의 고온 인장 및 피로특성

Purpose: This study aims to determine the most suitable material for heat exchangers by analyzing the tensile and fatigue strengths of different types of stainless steel, i.e., AISI 310S, AISI 316L, and AISI 347 after welding and aging at both room and high temperatures. BRMethods: Tensile and fatigue tests were performed on three types of stainless steel for heat exchangers using samples aged at 800℃ for 1000 hours and samples that were welded and aged at both room temperature and 800℃. The microstructures of the base material and aged samples were observed using an optical microscope and SEM. The fatigue tests were conducted using a stress ratio of 0.1 and a stress constant test; the fracture surface was then observed using SEM.BRResults: Chromium carbides tend to precipitate more in aged stainless steel samples than in the base material. It was found that AISI 316L stainless steel has the best elongation and fatigue strength at room temperature and 800℃.BRConclusion: In terms of aged and welded samples, AISI 316L stainless steel has the highest elongation and endurance limit. In particular, it has the smallest amount of chromium carbide precipitation at 800℃. In conclusion, it is determined to be an excellent heat exchanger material in terms of weldability, formability, and durability.

Investigation of the Dynamic Strain Aging Effect in Austenitic Weld Metals by 3D-DIC

Austenitic stainless steels similar to type AISI 316L are widely used structural materials in current and future nuclear reactors. Careful development and characterization of these materials and their welds is needed to verify the structural integrity of large-scale multicomponent structures. Understanding the local deformation behavior in heterogeneous materials and the mechanisms involved is key to further improve the performance and reliability of the materials at the global scale and can help in developing more accurate models and design rules. The full-field 3D digital image correlation (3D-DIC) technique was used to characterize two 316L multi-pass welds, based on cylindrical uniaxial tensile tests at room temperature, 350 °C, and 450 °C. The results were compared to solution annealed 316L material. The inhomogeneous character and dynamic behavior of the 316L base and weld materials were successfully characterized using 3D-DIC data, yielding high-quality and accurate local strain calculations for geometrically challenging conditions. The difference in character of the dynamic strain aging (DSA) effect present in base and weld materials was identified, where local inhomogeneous straining in weld material resulted in discontinuous type A Portevin–Le Châtelier (PLC) bands. This technique characterized the difference between local and global material behavior, whereas standard mechanical tests could not.

Improvement of sensitization and intergranular corrosion of AISI type 304L stainless steel through thermo-mechanical treatment

In this study, solution annealed AISI type 304 L stainless steel (SS) was thermo-mechanically processed (TMP) by introducing different cold-rolled 20 and 40 percentages, followed by annealing at 900 °C and water quenching. Sensitization was carried out by heat treatment for 24 h at 675 °C. The degree of sensitization (DOS) was measured by the electrochemical double loop potentiokinetic reactivation (DL-EPR) technique, indicating high DOS (12.5%) for the as-received specimen. The grain boundary engineering (GBE) by TMP treatment substantially lowered the DOS (7.1%) and resistance against intergranular corrosion (IGC) in a boiling nitric acid medium.

The natural frequencies of AISI 316 stainless steel and analytical simulation of a Lamb wave excited by a point source

Monitoring and analysis of acoustic emissions (AEs) generated by material defects is important during nondestructive testing. Here, we characterize the AEs generated during tensile deformation of AISI type 316 stainless steel (SS). The active frequencies of this SS, spanning the 100–200 kHz range, were determined via tensile testing. Fast Fourier Transform (FFT) analysis revealed that the AEs featured four frequency components representative of all signals observed during the strain-hardening stage. For completeness, the propagation of the AE wave, a Lamb wave generated by the point source, was simulated (using the determined frequency components) in a two-dimensional 2 × 80 mm SS plate. The displacement fields that triggered AE of a Lamb wave from a point source were derived by solving the Navier-Lamé equation. This analytical modeling of AE is useful for characterizing emission generated by defects.

Effect of Some Environmental and Stainless Steel Metallurgical Variables on the Values of Degree of Sensitization Measured by the Double Loop-Electrochemical Potentiokinetic Reactivation Test

The double loop-electrochemical potentiokinetic reactivation (DL-EPR) method estimates the degree of sensitization in stainless steels with ir/ia, the ratio of peak current densities during reactivation (reverse) and activation (forward) scans. Beyond sensitization level, other metallurgical variables, like inclusion content and cold work, or testing environment variables, like solution deaeration and solution aging, could potentially affect ir/ia. Austenitic stainless steel Types AISI 304 (UNS S30400) and AISI 303 (UNS S30300) were tested to assess the effect of those secondary variables on ir/ia. AISI 303 stainless steel had similar chromium and nickel contents to AISI 304, but higher contents of sulfur, resulting in a higher volume fraction of inclusions. ir/ia increased with inclusion content and decreased with cold work in AISI 304 stainless steel. In all cases, the DL-EPR test could discriminate solubilized from thermally aged specimens because confidence intervals of respective samples never overlapped. The testing solution was 0.5 mol/L H2SO4 + 0.01 mol/L KSCN, (sulfuric acid and potassium thiocyanate solution) and a common practice is to freshly prepare it just before the test. Measurements are usually performed under deaerated conditions. However, deployment of the technique, especially in the field, could be facilitated if naturally aerated solutions prepared in advance in a laboratory can be used. The oxygen content in solution and solution aging did not have a statistically significant effect on ir/ia.

Formation and Breakdown of Oxide Films in High-Rate Anodic Dissolution of Chromium–Nickel Steels in Electrolytes for Electrochemical Machining

It is shown that, in high-rate pulsed galvanostatic anodic dissolution of type CSN17335 and AISI 304 chromium–nickel steels in electrolytes for electrochemical machining (ECM) (chloride, nitrate, and mixed chloride–nitrate solutions with a conductivity of 0.15 S/cm) using microsecond pulses with a duration of 20–2000 μs and current densities in the range of 1–100 A/cm2, a substantial fraction of charge (up to ~40%) is spent on the formation of a passivating oxide film with a semiconducting behavior. The electrochemical treatment therefore directly involves the oxide film, not the alloy. As a consequence, the current efficiency of ECM of these materials is ~60–70%, depending on the alloy composition. When using direct current, the rate of machining increases as a result of the oxide film breakdown due to its thermokinetic instability (“thermal explosion”) caused by a rise in the surface temperature.

Influence of long term Sodium Exposure on the Corrosion and Tensile Properties of AISI Type 316LN stainless steel and modified 9Cr-1Mo steel

AISI Type 316LN stainless steel (SS) and modified 9Cr-1Mo (P91) steel are used in the intermediate heat exchanger and steam generator (SG), respectively of prototype fast breeder reactor (PFBR). This paper presents the effect of long-term sodium exposure (50000 h) on the corrosion and tensile properties of 316LN SS and P91 steel. The results showed that the prolonged sodium exposure of 316LN SS can lead to selective leaching of alloying elements (depletion of Cr, Ni, and Mo), enrichment of Fe, formation of ferrite layer and carburized zones with increased hardness at the surface (272 HV), and a reduction in ductility by nearly 40 %. Double-loop electrochemical potentiokinetic reactivation (DLEPR) results of sodium exposed 316LN SS showed a 25% higher degree of sensitization (DOS) as compared to thermally aged one. The microstructural examination of sodium exposed 316LN SS revealed a ditch structure near the surface and carbide precipitates along the grain boundaries indicating the diffusion of carbon through grain boundaries and surface carburization. XRD studies of sodium exposed 316LN SS revealed predominant phases of ferrite and Cr23C6 phases, which further corroborated the results of DLEPR, microstructure, and hardness data. The sodium exposed P91 steel showed no significant microstructural, microchemical changes and tensile properties after sodium exposure. The carbon depth profiles carried out using SIMS in sodium exposed 316LN SS and P91 steel showed a surface carbon concentration of 0.85 and 0.32 wt.%, respectively. Fractography of sodium exposed 316LN SS showed intergranular fractures whereas the fractographs of P91steel showed fibrous dimple and cleavage type of fractures indicating the growth of carbides. The present results confirm that P91 steel can sustain the reactor life in flowing sodium containing 25 ppm carbon and less than 2 ppm oxygen.

High Density RF-DC Plasma Nitriding under Optimized Conditions by Plasma-Diagnosis

This paper is concerned with plasma diagnosis on a N2-H2 gas mixture to determine the optimum parameters for the nitriding process. Plasma parameters such as pressure, RF-voltage, and DC-bias were varied for optimization. The active species such as N2+ and NH were identified in plasma diagnosis. In the N2-H2 gas mixture, hydrogen imposed a great influence on plasma generation. The small addition of a hydrogen molecule into the gas mixture resulted in the highest yield of N2+ ions and NH radicals; the optimum hydrogen content was 20% in the mixture. The austenitic stainless-steel type AISI304 was nitrided at 673 K and 623 K to experimentally demonstrate that hydrogen gas content optimization is necessary to improve the surface hardness and to describe low temperature nitriding under high nitrogen flux at the surface.

The Role of Grain Refinements and Γ Irradiation on Corrosion Resistance of Aisi Type 304l Stainless Steel for the Application in Back-End of the Nuclear Fuel Cycle

The Role of Grain Refinements and Γ Irradiation on Corrosion Resistance of Aisi Type 304l Stainless Steel for the Application in Back-End of the Nuclear Fuel Cycle

Comparison of the master sinter curves of water- and gas-atomized AISI 4340 low-alloy steel in binder jetting additive manufacturing

Master sinter curves (MSC) are empirically derived models used to predict bulk densification behavior of a powder-compact exposed to heat in a controlled nitrogen-hydrogen atmosphere. In this study, solid-state sintering MSC models were developed for two types of AISI 4340 powders: water-atomized and gas-atomized, which were deployed in binder jetting additive manufacturing. The models were constructed based on shrinkage measurements obtained through push-rod dilatometry. The results showed that the bulk densification behavior of the water-atomized parts was generally similar to the gas-atomized, indicating its relevance in BJAM when it comes to sintering. Some of the differences in bulk densification were attributed to the powder organization in the green state. The water-atomized powder was found to have a larger activation energy value (341 kJ/mol) than that of the gas-atomized (312 kJ/mol) and exhibited a slightly slower densification rate. The models were validated through independent sintering trials, resulting in model prediction accuracies of 91.2% and 99.4% for the water- and gas-atomized powders respectively. The starting green densities in the validation trials were 49% and 50% respectively, with final density targets of 70–73%. Examination of validation samples from both powders revealed similar particle necking behavior. Further optimization of the powder spreading for WA powders may maximize the powder packing and further improve the densification rate.

Research regarding strip cladding of heat-resistant SA 387 Gr.11Cl.2 steel type

The continuous development of industrial processes in the petrochemical field requires the use of materials with anticorrosive properties, able to withstand working conditions at high temperatures but also in highly corrosive environments. The basic materials with anticorrosive properties have a high cost price which leads to the need to find alternative manufacturing solutions. In such situations, the use of bimetal plates or the option of welding cladding with an anticorrosive layer of the base material is used. The paper analyses the possibility of strip cladding using the submerged arc welding process of a reactor made of SA 387Gr11Cl.2 basic material, a heat-resistant alloy steel. To achieve the deposition of the appropriate anticorrosive layer (stainless steel type AISI 347) it was necessary to use a buffer layer made of austenitic stainless-steel type 309L. In order to eliminate the internal tensions appeared after the cladding process, the sample was subjected to a stress relieving heat treatment. After the heat treatment, the sample was subjected to non-destructive examinations (visual and penetrant testing) but also to destructive examinations specific to the approval tests of cladding technology (Metallographic tests, Vickers hardness test, bend test, ferrite number, chemical composition). Metallographic tests of cross-sectional phase structures were carried out in macroscopic and microscopic terms. In the area of the deposited material can be observed a typical austenitic casting structure resulting from the use of a high linear energy, specific to the automatic submerged arc welding. Following the performance of hardness measurements made in the characteristic areas of the deposition, it can be seen that there was a slight increase in the values obtained in the heat affected zone, without exceeding the prescribed values for the materials used. Following the analysis of the results obtained from the specific examinations and tests to the plated samples, it can be seen that they are within the limits prescribed by the standards in force regarding the approval of the cladding technology used.

Electrochemical Investigations of Steels in Seawater Sea Sand Concrete Environments.

Seawater and sea sand concrete (SWSSC) is an environmentally friendly alternative to ordinary Portland cement concrete for civil construction. However, the detrimental effect of high chloride content of SWSSC on the corrosion resistance of steel reinforcement is a concern. This study undertook the electrochemical corrosion behaviour and surface characterizations of a mild steel and two stainless steels (AISI type 304 and 316) in various simulated concrete environments, including the alkaline + chloride environment (i.e., SWSSC). Open circuit potential (OCP), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were employed. Though chloride is detrimental to the corrosion resistance of mild steels, a simultaneous presence of high alkalinity in SWSSC negate the detrimental effect of chloride. In the case of stainless steels, a high level of alkalinity is found to be detrimental, whereas chloride seems to have less detrimental effect on their corrosion resistance.

Effect of the variation of the electrodeposition time of hydroxyapatite/chitosan coatings on AISI 316L SS

Type AISI 316 L Stainless Steel (316 L SS) plays a crucial role in bone replacement surgery due to its excellent mechanical features, availability at low cost, and ease of fabrication, but its performance is low when in contact with the aggressive conditions of the human body fluids. Chitosan (CTS) is a biopolymer that blended with hydroxyapatite (HAp) could form coatings to improve surface properties of a metallic orthopedic prosthesis, i.e., corrosion-resistance to the base metal and biocompatibility of the ceramic on the metal surface. This work aims to obtain and evaluate HAp/CTS composite coatings deposited on the surface of AISI 316 L SS substrate by electrophoretic deposition (EDP) technique. The influence of the time of deposition on the coating’s characteristics and properties was characterized and discussed. The coatings were structural, elemental, and chemically characterized using X-Ray diffraction and Raman spectroscopy. HV values in a range of 64.7 to 111.5 were observed, showing the lowest HAp/CTS-30.0 coating values for all the loads applied. The lowest HV value was nearby to the reported value for human bone’s hardness, around 47HV; considering that the coating will be in constant contact motion with the bone surface, the contact with a softer surface could decrease the wear on the human bone. The hardness decreases with the coating thickness’s increment because the coating presented a higher plastic deformation than the 316 L SS surfaces. A decrease in the roughness average (Ra) was well noticed as the deposition time increased; meanwhile, the thickness increased as the deposition time increased.

The Effect of Electrical Discharge Machining Total Heat Generated on White Layer Thickness (WLT) and Fatigue Life for Die Steel

The present paper concerns with studying the high complexity nature of the EDM multiple discharge analysis transformed into a feasible solvable mathematical model for the die steel workpiece type AISI D2, the copper and graphite materials electrodes, and the kerosene dielectric by setting the Transient Thermal and the Multiphysics analyses domain loads models using the ANSYS 15.0 finite element analysis. Two load steps modeled the entering setting time analysis, six sub-periods setting time cycle, four heating, and two cooling periods, six transient temperature values, and four transient thermal convection models. The radius spark (discharge channel), the total number of discharges sparks, the total heat power generation, the absorbed heat flux fractions by the electrodes, the workpieces and kerosene fluid dielectric, the heat-affected zones (HAZ), the hard white recast layer thickness (WLT) and properties, the workpiece fatigue safety factor and life after EDM machining were determined and simulated. The thermal model errors compared with theoretical calculations and a modeled predicted equation were also deduced and verified. The experimental results evinced that the maximum total heat flux generated using the graphite material electrodes is (2.619E+009 W/m2) which is higher than when using copper material electrodes by (82.4%), while the minimum value of the white layer thickness (WLT) after EDM machining using graphite tool electrodes is (8.34 μm), which it gives an improvement comparing with using of copper tool electrodes by (40.0%). The macrographic and microstructure evaluation manifest that the discharge spark craters sizes when using graphite tool electrodes reached their sizes. The maximum fatigue stresses and fatigue safety factor when using copper tool electrodes are (240 MPa) and (0.89) which is higher by a value of (3.35%) and (3.45%) comparing with the using of graphite electrodes, respectively.