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An atmospheric plasma spray deposition process was adopted for coating regular-shaped, Stellite 6 powder directly on a rolled 3mm size AISI 304 austenitic grade stainless steel substrate without any intermediate bond layers. Coating thickness as measured in a scanning electron microscope was obtained as 74 $\mu$m, 128 $\mu$m, and 215 $\mu$m. An experimental investigation of the functional behavior such as corrosion, microhardness, and erosion of the coated steel at different operating temperatures was undertaken to determine the suitability of its application in the industry. Erosion tests were conducted in an air jet tribo-tester utilizing alumina as an erodent with normal impingement angle at room temperature, 300^∘C, and 600^∘C. It was difficult to identify a single coating thickness that can be satisfactorily used for superior erosive wear properties with corrosion resistance. So modern management tools such as tri-vector and technology sieve analysis procedures as identification techniques were adopted for the selection of the best coating thickness by complying with the mechanical, erosion, and corrosion resistance properties. Steel coated with 128-$\mu$m coating thickness provides the best result for a combination of functional characteristics.

Plasma spraying is a prospective method frequently employed because of its increased effectiveness in ceramic coatings. Optimizing process parameters is necessary to maximize the coating performance. This study employed response surface methodology (RSM) to investigate the impact of process variables, including current, powder feed rate, and standoff distance, on the porosity and corrosive wear loss of Cr₃C₂$+$8YSZ composite coating. Experiments were done using the central composite design method, and quadratic regression models were created for the responses based on the completed trials. All parameters are observed to be most significant as the obtained p-value is under the threshold of 0.05 as per the analysis of variance (ANOVA) calculations. The optimal plasma spray process parameters were determined to be 500 A of current, a powder feed rate of 46gm/min, and a standoff distance of 3 inches for the expected lowest corrosive wear loss of 0.000025mm/year and a reduced area percentage porosity value of 0.93.

Efficient and rapid annealing treatments are critical for the sustainable forming and manufacturing of metallic materials, as well as for energy conservation and emission reduction in the manufacturing industry. We investigate the impact of high-density pulsed electric current (HDPEC) treatment on the recovery of work hardening in pre-strained SUS316 stainless steel and clarify the role of the athermal effect. The pre-strained samples exhibited significant work hardening, characterised by increased strength and hardness. After HDPEC treatment, the work hardening was fully mitigated, primarily due to the fast dislocation annihilation and grain refinement induced by the HDPEC treatment. Additionally, equivalent and rapid heating samples were performed to distinguish the contributions of thermal and athermal effects to the recovery of work hardening. The results showed that higher current densities were more effective in alleviating work hardening, and under high current density conditions, the effect of athermal was greater than the thermal-related effect.

The characterization of the single crystal of type 304 stainless steels was performed by using particle induced x-ray emission and Rutherford backscattering spectroscopy with channeling technique (PIXE-C and RBS-C). They proved that the solution annealing process is absolutely necessary for production of a good single crystal of stainless steels.

They are also shown that the positions of P atoms before He irradiation were mostly substitutional sites of fcc structure and that MeV He ion irradiation induced segregation of Si and S atoms to the (110) surface.

To investigate the effect of TiN coating on the fatigue strength of high-strength steel, four-point bending fatigue tests were carried out for martensitic stainless steel with TiN film coated using arc ion plating (AIP) method. A 2-μm-thick TiN film was deposited onto the substrate surface under bias voltage of four kinds: V_B = 0, -60, -160 and -260 V. For V_B = 0, -160 V and -260 V, the fatigue limit increased. The highest fatigue limit of σ_max = 900 MPa was obtained for V_B = -160 V. But some samples for V_B = -260 V showed the decrease of fatigue limit due to film delamination during the fatigue test. For V_B = -60 V, the fatigue limit was unchanged by coating. As a result of a coating property analysis, the following conclusions were obtained. Fatigue crack propagation was almost independent of the bias voltage. Fatigue crack initiated from the subsurface in the substrate and the crack initiation behavior depended on the film property of the adhesion, residual stress, elastic modulus, and the film's hardness depended on the bias voltage especially for low fatigue stress level.

The surface properties like roughness etc. strongly influence the fatigue strength of high-tensile steel. To investigate the effect of surface condition and TiN coating on the fatigue strength of high-strength steel, four-point bending fatigue tests were carried out for martensitic stainless steel with TiN film coated using arc ion plating (AIP) method. This study, using samples that had been polished under several size of grind particle, examines the influence of pre-coating treatment on fatigue properties. A 2-µm-thick TiN film was deposited onto the substrate under three kinds of polishing condition. The difference of the hardness originated in the residual stress or thin deformation layer where the difference of the size of grinding particle of the surface polishing. And it leads the transformation of the interface of the substrate and the TiN film and improves fatigue limit.

Bacteria can attach to stainless steel surfaces, resulting in the colonization of the surface known as biofilms. The release of bacteria from biofilms can cause contamination of food such as dairy products in manufacturing plants. This study aimed to modify stainless steel surfaces with silver nanofilms and to examine the antibacterial effectiveness of the modified surface. Ion implantation was applied to produce silver nanofilms on stainless steel surfaces. 35 keV Ag ions were implanted with various fluences of 1 × 10¹⁵ to 1 × 10¹⁷ ions•cm^-2 at room temperature. Representative atomic force microscopy characterizations of the modified stainless steel are presented. Rutherford backscattering spectrometry spectra revealed the implanted atoms were located in the near-surface region. Both unmodified and modified stainless steel coupons were then exposed to two types of bacteria, Pseudomonas fluorescens and Streptococcus thermophilus, to determine the effect of the surface modification on bacterial attachment and biofilm development. The silver modified coupon surface fluoresced red over most of the surface area implying that most bacteria on coupon surface were dead. This study indicates that the silver nanofilm fabricated by the ion implantation method is a promising way of reducing the attachment of bacteria and delay biofilm formation.

Stainless steel surface was irradiated by linear polarized laser (800 nm, 35 fs, 4 Hz and 0.7 J/cm²) with different pulse numbers. Environmental scanning electron microscope (ESEM/EDS) was used for detailed morphology, microstructure and composition studies. The wettability of irradiated steel surface was tested by Interface Tensiometer JC-2000X and compared with untreated stainless steel. Results showed that micro/nanostripes with different periods were formed. The period increased with the increasing pulse numbers from 450 nm for 90 pulses to 500 nm for 180 pulses. The orientation of those stripes was parallel with the laser beam polarization. Nanoparticles were observed on those periodic structures. EDS indicated that the atomic ratio of Cr increased and the atomic ratios of Fe and Ni decreased after laser irradiation, which may enhance the corrosion resistance due to the Cr-rich layer. The prepared structure exhibited hydrophobic property without further treatment. The formation mechanism of micro/nanoperiodic structures was also explored.

Butt joining of AA6061 aluminum (Al) alloy and 304 stainless steel of 2-mm thickness was conducted using laser–MIG hybrid welding–brazing method with ER4043 filler metal. To promote the mechanical properties of the welding–brazing joints, two kinds of intermediate layers (Al–Si–Mg alloy and Ag-based alloy) are used to adjust the microstructures of the joints. The brazing interface and the tensile strength of the joints were characterized. The results showed that the brazing interface between Al alloy and stainless steel consisted of double layers of Fe₂Al₅ (near stainless steel) and Fe₄Al${}_{13}$ intermetallic compounds (IMCs) with a total thickness of 3.7 $\mu$m, when using Al–Si–Mg alloy as the intermediate layer. The brazing interface of the joints using Ag-based alloy as intermediate layer also consists of double IMC layers, but the first layer near stainless steel was FeAl₂ and the total thickness of these two IMC layers decreased to 3.1 $\mu$m. The tensile strength of the joints using Al–Si–Mg alloy as the intermediate layer was promoted to 149 MPa, which was 63 MPa higher than that of the joints using Al–Si–Mg alloy as the intermediate layer. The fractures occurred in the brazing interface between Al alloy and stainless steel.

Structurally colored stainless steel (SS) surfaces were produced by using femtosecond laser at normal incidence at ambient conditions. The influence of laser polarization on the surface properties was investigated. The surface morphologies, roughness and color of the laser-treated surface were characterized by using environmental scanning electron microscope (ESEM), roughmeter and atomic force microscope (AFM). Results indicated that the circular polarization leads to more random structures than the horizontally linear polarization. Specimen with the highest surface roughness shows the brightest color. Different colors are cyclically exhibited by changing view angles due to different orders of diffraction. This investigation developed the technique of using femtosecond laser in situ preparation of periodic structures on 304 SS, and indicating that laser polarization is an important parameter to control surface structures to achieve different colors.

The simulation and process optimization for laser marking of submillimetre rasterizing 2D code on stainless steel are investigated. For 50CrVA stainless steel, the temperature field of material during laser marking is obtained by numerical modeling. The results show that temperature change in the depth direction and oxidation degree of laser radiation region are the fundamental reasons for the contrast of 2D code, but the temperature change occurs in the radius direction for the print growth. The threshold of laser average power and $Q$ frequency for an identifiable submillimetre 2D code are, respectively, 3.0 W and 100 KHz, which matches the simulation well within normal operating conditions. It is also found that an increase of the pulses number effectively improves the contrast and the appearance consistency of modules in DM code. Besides, corrosion tests show that the corrosion resistance of submillimetre 2D code is greatly improved by covering a layer of transparent polyurethane coating. Finally, a sample of submillimetre 2D code marked on cylindrical tool with diameter of 1 mm is obtained. In conclusion, the method could obtain submillimetre code with high reading quality and corrosion resistance by minimizing the characteristic edge over-burn effects, which provides theoretical basis and experimental method for identification of small parts.

In this study, the parameters for underwater laser cutting of 50-mm thick stainless steel, which is typically used in nuclear power structures, are investigated. The focal position of laser beam significantly affects the cutting quality. In particular, in the cutting of the thick sample, change in the focal position determines the kerf width and the roughness of the cut surface. Moreover, the effects of the variation of kerf width and the cut surface characteristics on the focal position of the laser beam are investigated. As the focal position moved to the inside of the material, the upper kerf width increased, but the quality of the cut surface was improved.

The selective laser melting (SLM) process gives a possibility to create complex shape parts. Joining SLM alloy parts to similar or dissimilar alloy parts can overcome some product design limitations such as limited dimensions and residual stress concentration. In this study, successful electron beam joining work on to SLM AISI 304 stainless steel plates was performed. The influence of beam current on the weld bead profile was investigated. Typical welded joints were analyzed by microstructure, microhardness, and tensile tests. The optimal welding parameters were obtained accordingly. A thorough analysis of the element and microstructure distribution in SLM and its influence on the properties of the welded joints were also investigated.

In this work, two types of models for a closed-cell Al foam with 80% porosity were established by Digimat and ABAQUS. The compression characteristics of the Al foam-filled stainless steel tube structure with both Al foam models were simulated and compared in combination with experiments. The results showed that Al foam-filled tubes presented higher peak compressive force compared with unfilled stainless steel tube. Compared with the crushable Al Foam model established by ABAQUS, the Digimat model could intuitively observe the plastic deformation in the cells of the Al foam-filled structure. However, the simulated results derived from Digimat software were slightly different from the experimental result. In general, the crushable-foam model embedded in ABAQUS can better match the experimental results from a macro perspective.

Stainless steel (SS) is widely used in many fields including aeronautics, automobiles, marine and mechanical industries due to its outstanding feature such as good corrosion resistance and hardness. However, changes in material properties under stress, particularly changes in Young’s modulus, result in the formation of cracks, a reduction in load-bearing capacity, and fatigue damage. So, the structural integrity needs to be evaluated based on a precise measurement of mechanical properties. In this study, Stainless Steel 304 (SS-304) is used as the base material and various tensile stresses are applied ranging from 0MPa to 100MPa with increment of 10MPa in each step. Nondestructive Laser Ultrasound Technique (LUT) has been used to characterize the elastic modulus under various tensile stresses. An inverse program was developed based on the Particle Swarm Optimization (PSO) algorithms to determine material properties. Nonlinear Gauss fitting method was proposed and established the fitting equation and nonlinear curve for Young’s modulus and residual stress. The outcome of this research shows that when tensile stress is applied, the mechanical properties decrease by shifting the dispersion curve and also it is evident that the dispersion curves move toward the high-frequency-thickness while increasing the tensile stress. When the tensile stress was increased from 0MPa to 100MPa, the value of Young’s modulus decreased from 201.7GPa to 193.5GPa. Especially, the predominant changes were observed during 30–100MPa. This observation displays the bonding strength and binding energy between the atomics. Further, the proposed nonlinear Gauss fitting substantiated the experimental values and confirmed that the thickness accuracy is close to the inversion values, with an average difference of 4.32%. This research suggests a potential nondestructive method to determine the residual stress of a material by calculating the changes in the elastic modulus.

Stress relaxation rate in un-irradiated and neutron-irradiated 303 stainless steel was investigated at room temperature. The specimens were exposed to 100 mC, Ra-Be neutron source of continuous energy 2–12 MeV for a period ranging from 4 to 16 days. The tensile deformation of the specimens was carried out using a Universal Testing Machine at 300 K. During the deformation, straining was frequently interrupted by arresting the cross head to observe stress relaxation at fixed load. Stress relaxation rate, s, was found to be stress dependent i.e. it increased with increasing stress levels σ₀ both in un-irradiated and irradiated specimens, however the rate was lower in irradiated specimens than those of un-irradiated ones. A further decrease in s was observed with increase in exposure time. The experiential decrease in the relaxation rate in irradiated specimens is ascribed to strong interaction of glide dislocations with radiation induced defects. The activation energy for the movement of dislocations was found to be higher in irradiated specimens as compared with the un-irradiated ones.

Ti(C, N) coatings were prepared on stainless steel (SS) substrates by plasma surface alloying technique. Carbon–nitrogen co-doped titanium dioxide (C-N-TiO₂) coatings were fabricated by oxidative of the Ti(C, N) coatings in air. The prepared C-N-TiO₂ coatings were characterized by SEM, XPS and XRD. Results reveal that the SS substrates were entirely shielded by the C-N-TiO₂ coatings. The C-N-TiO₂ coatings are anatase in structure as characterized by X-ray diffraction. The tribological behavior of the coatings was tested with ball-on-disc sliding wear and compared with substrate. Such a C-N-TiO₂ coatings showed good adhesion with the substrate and tribological properties of the SS in terms of much reduced friction coefficient and increased wear resistance.

In this paper, corrosion behavior of an AISI 304 stainless steel modified by niobium or niobium nitride (denoted as niobized 304 SS and Nb-N 304 SS, respectively) is investigated in simulated solid polymer fuel cell (SPFC) operating conditions. Potentiodynamic polarizations show that the corrosion potentials of surface modified 304 SS shift to positive direction while the corrosion current densities decrease greatly comparing with the bare 304 SS in simulated anodic SPFC environments. The order of corrosive resistance in corrosive potential, corrosive current density and pitting potential is: Nb-N 304 SS > niobized 304 SS > bare 304 SS. In the methanol-fueled SPFC operating conditions, the results show that the corrosion resistance of bare and niobized 304 SS increases with the methanol concentration increasing in the test solutions.

In order to research the influence of friction conditions on the sheet metal deformation behavior under the fluid pressure, the experimental method that can test the relationship between fluid pressure and wall thickness was proposed in this paper. The theoretical model about the quantitative variation relationship between fluid pressure and wall thickness together with the theoretical model about the quantitative variation relationship between friction coefficient and wall thickness, was obtained by theoretical derivation. At the same time, it could be concluded that friction contact region close to the tensile end was easier to satisfy the plastic yield criterion. Therefore, the plastic deformation initially occurred at this area and fracture emerged on account of excessive reduction of the sheet thickness. Simulation analysis with 304 stainless steel was carried out. The result indicated that the capacity of sheet uniform deformation decreased with the increasing of the friction coefficient. When the friction coefficient increased from 0.08 to 0.20, the uniform elongation decreased by 32%. But when other conditions were kept unchanged, the greater the fluid pressure was, the thinner the sheet would be. Experiments indicated that the necking and fracture appeared in the gauge length near the tensile end with different lubricants. And these provided a theoretical basis for the process and device design of sheet metal hydroforming.

Bulk micro/nanostructured 304 austenitic stainless-steel plates with bimodal grain size distributions were prepared by Alumina Thermite Reaction at various temperatures and extents of rolling deformation. Rolling cogging of the sheet was performed with a rolling reduction of 40% at 1000${}^{\circ }$C followed by rolling reduction of 80% at 700${}^{\circ }$C. The strength and plasticity of the resulting micro/nanostructured 304 stainless steels with bimodal grain size distribution achieved the best matching, with tensile strength, yield strength, and elongation of 1410 MPa, 723 MPa and 15.3%, respectively. To better understand the deformation mechanism of this micro/nanostructured stainless steel sample, an in situ scanning electron microscopy technique was adopted. The crack initiation, propagation, and fracture were dynamically observed and recorded during the tensile deformation. Our results revealed that a stress concentration near the preset notch served as the initiation source and that microcracks were formed in the grain boundaries between micro- and nano-grains and then spread to the microcrystalline region until passing through the microcrystalline region or until passivation occurred in the microcrystalline region. The microcracks not only caused serious damage to the specimen but also generated back stress, which could lead to hardening of material, thereby enhancing the global ductility. Finally, the mechanism responsible for the enhanced plasticity and strength of the micro/nanostructured 304 stainless steel with a bimodal grain size distribution was analyzed and combined with the fracture morphology.