Grade Stainless Steel Research Articles

Oxidative corrosion resistance of a CrxFeyNi1-x-y composition spread alloy film (CSAF) in dry air

Composition Spread Alloy Films (CSAFs) were used to study the resistance to oxidative corrosion of CrxFeyNi1-x-y alloys in dry air and determine the critical Cr composition, xCr∗, necessary to prevent bulk oxidation. CrxFeyNi1-x-y CSAFs were made using physical vapor deposition (PVD) and then oxidized in dry air between 100 – 500 °C for periods of 1 h. A sharp passivation boundary was observed at 300 °C separating alloys showing evidence of heavy oxidation from Cr-rich alloys that were passivated. X-ray photoelectron spectroscopy (XPS) depth profiling was used to measure the extent of oxidation and penetration depth of the oxide layer on either side of the passivation boundary. XPS measurements confirmed the presence of a critical Cr composition, xCr∗, ranging from 18 to 26 at.%. For alloys with xCr≥xCr∗, a sufficiently thick passivating layer of oxidized Cr, Cr(ox), had formed on the top surface preventing the oxidative corrosion of either Fe or Ni. On the other hand, when xCr<xCr∗, bulk oxidation was observed, with appreciable Fe(ox) and/or Ni(ox) measured on the surface and often penetrating through the entire alloy film thickness. The trajectory of xCr∗ plotted within CrxFeyNi1-x-y composition space supports the trend towards using higher Cr-content stainless steel grades in harsh oxidative environments.

Comparison of electrolytic etching and immersion etching for 304L, 316L and 347 austenitic stainless-steel grades

Comparison of electrolytic etching and immersion etching for 304L, 316L and 347 austenitic stainless-steel grades

Wettability, morphological, miscibility characterization of alginate, and chitosan-based bio composite coatings

This study is aimed at fabricating composite biocompatible coatings of Alginate (Alg) and Chitosan (CS) on a stainless steel (grade 316L) substrate, reinforced with several percent nanoparticle additives, Using a dip coating method. The research used Fourier Transform Infrared (FTIR), field emission scanning electron microscopy (FESEM), and Atomic force microscopy (AFM) to explore surface roughness, size dispersion, and surface topography. The introduction of nanoparticles enhanced the wettability of the CS/Alg coatings. Notably, nanoparticle coatings with TiO2, Nb2O5, and biotin showed exceptional wettability due to the hydrophilic qualities of the matrix and reinforcements. This was corroborated by contact angle measurements, which confirmed the hydrophilic nature of the chitosan-alginate blend. The FTIR results highlighted the noticeable compatibility between CS-Alg and (TiO2, Nb2O5, and biotin) nanoparticles. No discernible alterations in the wavelengths were observed. Employing biotin-TiO2-Nb2O5, the FESEM showed that the biocompatible coating films were uniform and devoid of cracks on the 316L stainless steel substrate. The matrix + TiO2, matrix + Nb2O5, matrix + TiO2 + Nb2O5, and matrix + TiO2 + Nb2O5 + biotin-coated 316L stainless steel showed roughness data of 4.14, 5.28, 7.04, and 8.02 nm, accordingly, in contrast with the neat chitosan/alginate coating, which displays 2.67 nm, suggesting the significant impact of biotin and oxides on surface topography. These findings underscore the potential of the developed nanoparticle coatings for orthopedic applications, with enhanced wettability and biocompatibility. Biocompatible coatings emerging from this research are promising for advancing orthopedic and biomedical devices as they are used in scientific studies because of their biocompatibility with human tissues.

Fatigue-induced fracture assessment for duplex stainless steel protruding tube-to-tubesheet welded joints in multiple-tube test specimen

A novel fatigue testing result and its numerical discussions are presented for protruding tube-to-tubesheet welded joints. The welded joint specimen is made up of an innovative stainless steel grade for pressure vessels of urea production plant, i.e., duplex stainless steel (DSS). Multiple-tube test specimen in which a bundle of tubes fabricated to the tubesheet by welding, is employed. During the fatigue test, several initial cracking positions were observed from the central tube and surrounding tubes. The crack propagation (CP) phenomena, i.e., CP from the central tube to surrounding tube and from the surrounding tube to central tube, were characterized for the multiple-tube problem. Two types of fracture pattern were occurred. These distinctive cracking behaviors are studied using numerical analyses, i.e., FEM stress analysis and X-FEM CP simulation. The possible crack initiating positions as well as the fracture patterns are identified based on the stress distributions. The CP behaviors between the tubes are carefully examined using stress intensity factor (SIF). Additionally, fatigue life cycles and fatigue resistance of the specimen are discussed. The fatigue-induced fracture of the DSS specimen is rigorously investigated and presented using the experimental and numerical methods.

Enhanced Hemocompatibility and Cytocompatibility of Stainless Steel.

The present study introduces an advanced surface modification approach combining electrochemical anodization and non-thermal plasma treatment, tailored for biomedical applications on stainless steel grade 316L (SS316L) surfaces. Nanopores with various diameters (100-300 nm) were synthesized with electrochemical anodization, and samples were further modified with non-thermal oxygen plasma. The surface properties of SS316L surfaces were examined by scanning electron microscopy, atomic force microscopy, X-ray photoemission spectroscopy, and Water contact angle measurements. It has been shown that a combination of electrochemical anodization and plasma treatment significantly alters the surface properties of SS316L and affects its interactions with blood platelets and human coronary cells. Optimal performance is attained on the anodized specimen featuring pores within the 150-300 nm diameter range, subjected to subsequent oxygen plasma treatment; the absence of platelet adhesion was observed. At the same time, the sample demonstrated good endothelialization and a reduction in smooth muscle cell adhesion compared to the untreated SS316L and the sample with smaller pores (100-150 nm). This novel surface modification strategy has significant implications for improving biocompatibility and performance of SS316L in biomedical applications.

Diffusion Bonding 321-Grade Stainless Steel: Failure and Multimodal Characterization.

Vacuum diffusion-bonded printed circuit heat exchangers are an attractive choice for the high-temperature, high-pressure demands of next-generation energy applications. However, early reports show that the high-temperature materials desired for these applications suffer from poor bond strengths due to precipitation at the bond line, preventing grain boundary migration. In this study, a diffusion bond of the high-temperature stainless steel grade 321H is investigated, and poor mechanical properties are found to be caused by Ti(C, N) precipitation at the bond line. Through in situ studies, it is found that Ti diffuses from the bulk to the mating surfaces at high temperatures. The Ti subsequently precipitates and, for the first time, an interaction between Ti(C, N) and Al/Mg-oxide precipitates at the bond line is observed, where Ti(C, N) nucleates on the oxides forming a core-shell structure. The results indicate that small amounts of particular alloying elements can greatly impact diffusion bond quality, prompting further research into the microstructural evolution that occurs during bonding conditions.

Implementation of different scanning strategy to improve the mechanical and wear properties of 15-5 PH stainless steel fabricated by laser-directed energy deposition

In this work, the effect of three different scan patterns (island scan pattern, island alternative scan pattern and cross-hatch pattern) on mechanical and wear properties is investigated for 15–5 Precipitation-hardened (PH) stainless steel by using laser-directed energy deposition (L-DED). Six rectangular blocks are deposited with constant laser power and scanning speed. Currently, studies on the control of anisotropic behavior to improve the mechanical and wear properties by using different scan strategy, especially in the case of 15–5 PH grade stainless steel is relatively sparse. Therefore, it is necessary to learn how mechanical and wear properties are improving in these three different scan pattern samples. At first, the temperature data at a specific point is captured by using a non-contact type pyrometer during printing and the detailed microstructural characterization of that particular region is analyzed. All three different scan pattern samples mostly show δ-ferrite and lath martensite (α') structure. The X-ray diffraction shows, there is formation of secondary precipitation phases like NbCr2, NbC, and Cu rich precipitation in all three different scan pattern samples. The electron back scattered diffraction (EBSD) result exhibits the island alternative scan pattern samples have mostly mixed orientation direction, a high fraction of retained austenite (͠ 0.004) and high angle grain boundaries (HAGBs) compared to the island scan pattern and cross hatch pattern samples. The island alternative scan pattern samples show maximum improved mechanical properties i.e. average ultimate tensile strength (UTS) of 1316 MPa and up to 20% of elongation amongst all deposited samples. Similarly, the alternative island scan pattern samples exhibit a high coefficient of friction (COF) irrespective of the applied load. The SEM image of the worn surfaces clearly demonstrates abrasion and adhesion type wear in all the three different scan pattern samples.

Surface Modifications of Medical Grade Stainless Steel

Medical-grade stainless steel (MSS) is one of the most widely used materials for implantable devices in biomedical applications, including orthopedic stents, dental implants, cardiovascular stents, cranial fixations, and surgical suture materials. Implants are exposed to corrosive body fluids containing chlorides, proteins, and amino acids, resulting in corrosion, wear, toxicity, inflammation, infection, and failure. MSS-based materials exhibit improved corrosion and mechanical resistance and suppress the degradation and release of toxic metal ions. Although MSS is manufactured with a passivating metal oxide layer, its anti-corrosion performance against chlorides and chemicals in body fluids is insufficient. Implants require biocompatibility, bioactivity, hemocompatibility, and sustainability. Antimicrobial activity and sustained drug release are also crucial factors. Therefore, stainless steel with desirable multifunction is in great clinical demand. This comprehensive review summarizes recent advances in the surface modification of MSS-based implants and their biomedical applications, especially in dentistry.

Superwettable surfaces and factors impacting microbial adherence in microbiologically-influenced corrosion: a review.

Microbiologically-influenced corrosion (MIC) is a common operational hazard to many industrial processes. The focus of this review lies on microbial corrosion in the maritime industry. Microbial metal attachment and colonization are the critical steps in MIC initiation. We have outlined the crucial factors influencing corrosion caused by microorganism sulfate-reducing bacteria (SRB), where its adherence on the metal surface leads to Direct Electron Transfer (DET)-MIC. This review thus aims to summarize the recent progress and the lacunae in mitigation of MIC. We further highlight the susceptibility of stainless steel grades to SRB pitting corrosion and have included recent developments in understanding the quorum sensing mechanisms in SRB, which governs the proliferation process of the microbial community. There is a paucity of literature on the utilization of anti-quorum sensing molecules against SRB, indicating that the area of study is in its nascent stage of development. Furthermore, microbial adherence to metal is significantly impacted by surface chemistry and topography. Thus, we have reviewed the application of super wettable surfaces such as superhydrophobic, superhydrophilic, and slippery liquid-infused porous surfaces as "anti-corrosion coatings" in preventing adhesion of SRB, providing a potential avenue for the development of practical and feasible solutions in the prevention of MIC. The emerging field of super wettable surfaces holds significant potential for advancing efficient and practical MIC prevention techniques.

AUGMENTATION OF DEPTH OF PENETRATION AND PRODUCTIVITY BENEFITS OF ATIG WELDS USING THE AHP

Weldability is an important issue in the fabrication of different grades of stainless steel used in industry. Tungsten inert gas (TIG) welding is widely used in industry for accurate and precision work, but lack of penetration is observed in this process even though current and welding speed can be varied considerably to increase heat input to obtain deeper penetration. Increased heat input adversely affects mechanical properties of the weldment. To overcome this, activated flux TIG welding is often used in industry to achieve higher depth of penetration with relatively less heat input. In this study, activated flux TIG welding is used with input variables such as heat input, welding speed and pulse frequency. The chosen base metal is SS 304L stainless steel, and a hybrid flux mixture containing fluxes of SiO2, MnO2 and MoO3 in a ratio of 1:1:2 is used to obtain the desired depth of penetration. Nine experimental runs are conducted to obtain the optimum depth of penetration. Heat input values are 2.767 kJ/mm, 1.470 kJ/mm and 1.281 kJ/mm and pulse frequency is 160 Hz, 120 Hz and 80 Hz. Welding speed varies from 0.5 mm/s to 1.18 mm/s. A maximum depth of penetration of 4.42 mm is achieved with a heat input of 2.767 kJ/mm, welding speed of 0.5 mm/s and pulse frequency of 160 Hz. The reversed Marangoni effect and arc constriction effect are the mechanisms responsible for the deeper penetration in ATIG welding. In this research, a multi criteria decision making tool, the Analytical Hierarchy Process (AHP), is used to validate the optimum value obtained. The optimal values obtained in the research are in good accordance with those obtained using the AHP. The outcome of the present investigation indicates the applicability of ATIG welding for joining large thickness of stainless steel flats to give enhanced productivity by reducing the number of weld passes.

Multi-objective optimization and evolution of dissimilar welding process between Cr-Mo steel and austenitic stainless steel for power plant application

In this study, response surface methodology (RSM) was employed to optimize the welding parameters’ effects on mechanical properties of dissimilar welds between Cr-Mo steel grade (P11) and austenitic stainless steel (AISI 316LN). To determine the best welding parameters, variance analysis (ANOVA), desirability function, and perturbation analysis were used to create regression models and identify the significant parameters influencing tensile strength and hardness gaps in the weld joints. The results indicated that welding speed is the most significant parameter affecting both the austenitic hardness gap and tensile strength, while gas flow has the most significant impact on the hardness gap of Cr-Mo steel. Furthermore, welding speed positively influences the mechanical properties of dissimilar weld, whereas welding current has a slight negative effect on tensile strength. The optimum welding parameters were found to be 130 A for welding current, 70 mm min−1 for welding speed, and 13 l min−1 for welding gas flow, resulting in hardness gap values of 18.10 HV (Stainless steel side), 27.38 HV (Cr-Mo steel side), and a tensile strength of 453.90 MPa. The optimum parameter effect is concentrated at the weld interfaces between the fusion zone and the heat-affected zone. This effect led to limitations in grain coarsening, a reduction in the martensite and delta ferrite phase percentages, a slight increase in the bainite ratio, and a decrease in carbide precipitations. As a result, a homogenization of strain distribution in the optimum weld was achieved, leading to ductile fracture in Cr-Mo steel.

Intergranular Corrosion Analysis of Austenitic Stainless Steels in Molten Nitrate Salt Using Electrochemical Characterization

This study investigates the influence of molten nitrate salt exposure on the intergranular corrosion (IGC) behavior of three grades of austenitic stainless steel (namely, AISI 304, AISI 304H, and AISI 321H). Two electrochemical techniques, double loop electrochemical potentiokinetic reactivation and potentiodynamic polarization methods, are applied after stainless steel is exposed to 600 °C molten nitrate salt, 60% NaNO3, and 40% KNO3 for varying immersion durations. Corrosion morphology is examined using optical microscopy and scanning electron microscopy images to assess susceptibility to IGC. IGC is prompted by the presence of chromium carbides at grain boundaries, which leads to chromium depletion around these carbides. The findings of the experiments reveal distinct IGC behavior among stainless steel grades. For AISI 304, the degree of sensitization (DOS) increases as exposure time progresses. However, AISI 304H and AISI 321H stainless steel exhibit diminishing DOS after 100 and 10 h of exposure, respectively. This trend is attributed to desensitization or the healing effect when stainless steel is exposed to molten salt for a prolonged time. The depletion and recovery of Cr near grain boundaries are confirmed by the inverse relationship to DOS of pitting potential.

Quantification of the Post-Fire Strength Retention Factors for Selected Standard Duplex and Lean Duplex Stainless Steel Grades.

The experimental quantification of retention factors related to the post-fire strength as well as the post-fire ductility of intentionally selected stainless steel grades applied in construction is the objective of the research presented here. These steel grades are characterized by a two-phase austenitic-ferritic microstructure of the duplex type. In this context, two mutually corresponding chromium-nickel-molybdenum steel grades are subjected to analysis, namely X2CrNiMoN22-5-3 steel belonging to the standard duplex group (DSS 22% Cr) and X2CrMnNiN21-5-1 steel belonging to the lean duplex group (LDSS). The similarities and differences in the mechanical properties exhibited by these steel grades after effective cooling, following more or less prolonged simulated fire action conforming to several development scenarios, are identified and indicated. The resistance of a given steel grade to permanent structural changes induced by the heating program proved to be the critical factor determining these properties and resulting in many cases in increased susceptibility to brittle fracture. The results obtained experimentally seem to confirm the quantitative estimates of post-fire retention factors forecast by Molkens and his team, specified for the steels exhibiting a duplex-type structure and tested by us. However, several of these estimates might be considered somewhat risky. Nevertheless, our results do not confirm the significant post-fire strengthening of steel grades belonging to the LDSS group following prior heating at a sufficiently high temperature, as reported earlier by Huang Yuner and B. Young.

A new approach to evaluate Ramberg-Osgood parameters for SS316LN using different types of specimens

A novel methodology is proposed for evaluating the stress-strain curve and determining the Ramberg-Osgood parameters (n, α) of SS316LN material. This involves utilizing load-displacement data from various specimen types, including both smooth and notched tensile specimens with different notch radii, in conjunction with finite element analysis. An error minimization method was used for evaluating the material parameters. The proposed approach for the evaluation of unique Ramberg-Osgood parameters provides a better result than that of the material stress-strain data of smooth specimen test. Ramberg-Osgood parameters were evaluated at two temperatures, i.e., 25°C and 650°C and compared with RCC-MRx code. Stress-strain equation as provided in the RCC-MR, can’t be used in FE analysis if the plastic strain exceeds 1.5% at certain regions of structure containing discontinuity, e.g., regions like shell-nozzle junction, vessel head, T-junction etc. The approach developed in this work shall help to obtain the material stress-strain curve over a wide range of plastic strain values. Ramberg-Osgood parameters were evaluated for the whole temperature range of 25°C and 650°C, which can be used for structural integrity analysis of reactor components made of stainless steel grade SS316LN. The range of applicability of data for RCC-MR code was extended beyond 1.5% of plastic strain in this work. The equations derived in this work shall be useful for structural integrity analysis and life assessment of structural components of nuclear reactors.

Optimization of welding parameters on weld deposits area in pulsed gas metal arc welding

This paper presents a methodology for optimising pulsed gas metal arc welding parameters on Stainless Steel GRADE 410. Most sectors favour the economic welding technique for its favourable outcomes, such as enhanced strength and reduced corrosion. Compared to conventional welding methods, pulsed gas metal arc welding has the advantage of reducing current consumption and increasing the rate at which metal is deposited. An optimisation technique is employed to forecast the weld bead's accurate geometry, penetration depth, and reinforcement height, considering the welding input parameters such as welding speed, current rate, and frequency level. The Taguchi technique uses experimental analysis by considering input and output parameters. A multiple regression analysis model has been developed for SS Grade 410 Stainless steel to determine the bead geometry's correctness.

Austenitic-to-austenitic-ferritic stainless steel transformation via PVD powder surface functionalization and spark plasma sintering

The present work investigates a new alloy design approach to elaborate stainless steel grades with an austenitic-ferritic microstructure. The originality of the study is the use, as starting material, of a 316 L austenitic powder coated by a thin chromium layer deposited by physical vapor deposition (PVD) technique. The coated powder was then consolidated by spark plasma sintering (SPS), a powder metallurgy process allowing the fast elaboration of dense materials with a fine-grained microstructure. The chromium coating, characterized by scanning and transmission electron microscopy, presents a columnar microstructure, formed by nanometric crystallites, well reproduced by the simulation of the film growth. The characterizations performed after sintering show that the initial austenitic powder particles are still visible in the bulk microstructure. On the other hand, a tetragonal σ phase enriched in chromium and molybdenum forms in the interparticular regions. After annealing treatment followed by quenching, the tetragonal phase transforms into the expected ferrite. The results prove that using a coated powder is a promising and innovative way to elaborate new steel grades with a two-phase austenitic-ferritic microstructure. This original approach can have the advantage of obtaining steels with a controlled microstructure and the desired amount of phases in the final bulk.

Duplex solar cooker with selective evacuated tube and compound parabolic concentrator

In the present work, an indirect solar cooking proposal is shown. The proposal combines three technologies: evacuated tubes, selective absorber, and compound parabolic concentrator (CPC). The absorber used is an evacuated glass tube, with a highly selectivity inner surface. The temperature reached by the solar cooker is approximately 160°C, enough to cover the cooking needs of all types of food; Irradiance, wind speed, ambient temperature was measured, food cooking tests were carried out, using an evacuated tube and a parabolic solar concentrator; as well as evacuated tube without parabolic solar concentrator. A compound parabolic concentrator was designed with an acceptance angle of 15 degrees, the base of the solar cooker was made with acrylic, the concentrator was made with simple reflection mirrors, the clips were printed on a 3D printer, the trays were made with food grade stainless steel, food cooking tests were carried out, recording the weather variables every 15 minutes. The development of this evacuated tube duplex solar cooker project is not only important because it involves the achievement of an academic purpose, but also involves a social purpose. It is intended to provide an efficient and economical solution that is attractive to multilateral organizations capable of supporting its manufacture, industrialization and distribution to achieve the massification of the product with a real and lasting impact

A Machine Learning Approach for Modelling Cold-Rolling Curves for Various Stainless Steels.

Stainless steel is a cold-work-hardened material. The degree and mechanism of hardening depend on the grade and family of the steel. This characteristic has a direct effect on the mechanical behaviour of stainless steel when it is cold-formed. Since cold rolling is one of the most widespread processes for manufacturing flat stainless steel products, the prediction of their strain-hardening mechanical properties is of great importance to materials engineering. This work uses artificial neural networks (ANNs) to forecast the mechanical properties of the stainless steel as a function of the chemical composition and the applied cold thickness reduction. Multiple linear regression (MLR) is also used as a benchmark model. To achieve this, both traditional and new-generation austenitic, ferritic, and duplex stainless steel sheets are cold-rolled at a laboratory scale with different thickness reductions after the industrial intermediate annealing stage. Subsequently, the mechanical properties of the cold-rolled sheets are determined by tensile tests, and the experimental cold-rolling curves are drawn based on those results. A database is created from these curves to generate a model applying machine learning techniques to predict the values of the tensile strength (Rm), yield strength (Rp), hardness (H), and elongation (A) based on the chemical composition and the applied cold thickness reduction. These models can be used as supporting tools for designing and developing new stainless steel grades and/or adjusting cold-forming processes.

Validating cyclic plasticity material model for three materials subjected to asynchronous axial-torsion conditions

In the present work, a cyclic plasticity model based on Ohno-Wang kinematic hardening rule and Tanaka non-proportionality parameter, is proposed to simulate the cyclic stress strain response of three materials. The proposed model has been validated with respect to reported test results on two grades of steel (SA 333 Gr. 6 and E355) and one grade of austenitic stainless steel (X5CrNi18-10) under asynchronous axial-torsion loading conditions with a wide range of frequency ratios. The proposed model resulted in a comparable assessment of axial and shear stress–strain response with respect to the test loops for all three materials.

Consideration of Temperature Factors when Designing Butterfly Check Valves for Hazardous Production Facilities

The safety of hazardous production facilities is directly related to the reliability of pipeline systems, which must be ensured regardless of environmental conditions. Accidents on pipeline sections can have catastrophic consequences associated with damage to human health and the environment. Damage to the metal of pipeline elements during operation due to internal corrosion occurring under the influence of the working fluid is one of the main reasons for failure. This study aims to develop an improved butterfly check valve (BCV), which is a pipeline element. For this purpose, various structural materials used in the production of check valves were analyzed, and the changes in their mechanical properties under the influence of temperature were also considered. Based on this material, a butterfly check valve was developed. The stress-strain state of the developed structure was assessed using the finite element method (FEM). Strains, stresses, and displacements were calculated to evaluate valve performance. These calculations are necessary to determine the most loaded elements of the BCV at the maximum and minimum ambient temperatures. The following conclusions were obtained: X6CrNiTi18-10 stainless steel grade is the most suitable material for piping systems transporting liquids in production facilities. On the basis of the simulation results, the values of equivalent stresses, maximum strains, and displacements were obtained. The research results confirmed the performance of the improved design, the unhindered motion of the working fluid in the working direction, and the convenient connection to horizontal and vertical sections of the pipeline. Doi: 10.28991/CEJ-SP2023-09-020 Full Text: PDF