Stainless Steel Alloy Research Articles

Efficient utilization of copper slag in an innovative sintering process for Fe–Ni–Cu alloy preparation and valuable elements recovery

In this study, copper slag and low-grade nickel laterite were synergistically utilized via an innovative sintering process with multi-force fields. Their sintering performance and the reduction and softening dripping characteristics of Fe–Ni–Cu product sinter were determined. The strengthening mechanism of the innovative sintering technology was revealed. The obtained Fe–Ni–Cu alloy and smelting slag from the melting dripping process were characterized. Carbon emissions reduction and other valuable elements treatment were also discussed. Due to the formation of the denser sinter microstructure and the reduction of high smelting components, sintering performances in the innovative sintering process are substantially improved. Compared with the base case, tumble index and productivity are improved by 24.87% and 19.59%, respectively. Solid fuel consumption is reduced by 27.14%. The reduction and softening dripping characteristics of Fe–Ni–Cu product sinter are excellent as well. The obtained Fe–Ni–Cu alloy with high purity can be used as the high-quality burden for copper-bearing stainless steel and high-strength alloy steel and its quality can be further improved by optimizing the smelting process parameters in the near future. In addition, the obvious carbon emissions reduction in sintering-blast furnace production can be achieved and other valuable elements such as S, Zn and Pb can be conveniently recycled in form of sulphuric acid and Pb–Zn dust, respectively.

Insight into Structural Changes and Electrochemical Properties of Spark Plasma Sintered Nanostructured Ferritic and Austenitic Stainless Steels.

Nanostructured ferritic (Fe(82−x)-Cr18-Six, x = 0–3 wt %) and austenitic (Fe(73−x)-Cr18-Ni9-Six, x = 0–3 wt %) stainless steel (SS) alloys were developed by mechanical alloying (MA) and spark plasma sintering (SPS). The unit cell parameter estimated from X-ray diffraction spectra exhibited a decreasing trend with an increase in wt % of Si content in both alloy systems. The particle size of powders estimated using bright field transmission electron microscopy images for ferritic (3 wt % Si) and austenitic (3 wt % Si) SS powders was found to be 65 ± 5 nm and 18 ± 3 nm, respectively. In case of the ferritic system, 3 wt % Si exhibited the highest densification (~98%) and micro-hardness of about 350.6 ± 11.2 HV, respectively. Similarly, for the austenitic system (3 wt % Si), maximum densification and micro-hardness values were about 99% and 476.6 ± 15.2 HV, respectively. Comparative analysis of potentiodynamic polarization, linear polarization, and electrochemical impedance spectroscopy results indicates an increase in electrochemical performance of both alloy systems as the wt % Si was increased. The increase in electrochemical performance is directly related to the increase in densification owing to Si addition in these alloys.

Tribotechnical properties of experimental hard alloys with modified cobalt binder

Introduction. This paper discusses tribomechanical characteristics of experimental hard alloys with a modified cobalt binder under friction without lubrication on hard-to-cut materials – stainless steel and titanium alloy. The research objective is to evaluate the process of friction interaction for each friction pair according to a number of parameters, and to determine the optimal combinations of “experimental hard alloy – structural material” on the basis of the established tribological indicators.Materials and Methods. Tribological tests of hard alloys were carried out using a cylinder-to-disc friction scheme for different sliding speeds and temperatures under constant load without the use of lubricants. Comparison of the friction interaction process was carried out by the frictional force, volumetric wear and roughness of the friction tracks on the counterbody. Stainless steel 12H18N9Т and titanium alloy ВТ3-1 were used as counterbody materials. The resistance of experimental compositions to the abrasive type of wear was determined through measuring the surface dynamic microhardness on a scanning nanohardness tester by analyzing the thickness of the scratches caused by the indenter.Results. According to the results of surface microindentation, the experimental alloys 2.22 (binder 5.65% Co + l.8% Mo + 0.6% Ti) and 2.23 (binder 5.1% Co + 2.7% Mo + 0.61 % Ti) are characterized by the highest microhardness. For these materials, the average scratch width at various forces was minimal. During tribological tests, the best frictional characteristics were recorded for stainless steel in combination with experimental alloy 2.22, and for the friction pair “titanium alloy VT3-1 — hard alloy 2.23”. The friction of this combination of materials was characterized by low friction coefficients with a low level of fluctuations, minimal wear of samples, and changes in the initial microrelief of their surfaces.Discussion and Conclusions. As a result of the research, the optimal friction pairs from the point of view of tribological interaction were established, specifically “titanium alloy VT3-1 — hard alloy 2.23” and “stainless steel 12X18N9T – hard alloy 2.22”. The frictional interaction for these combinations of materials is characterized by minimal volumetric wear, which will contribute to increasing the wear resistance of the tool in the areas of elastic contact on the front and rear surfaces.

Enhanced adhesion of anticorrosion ruthenium films deposited by RF sputtering on 304L stainless steel

Thin ruthenium films present an economical approach to corrosion protection of stainless steel alloys in reducing acidic environments. However, ruthenium films tend to spall and delaminate during corrosion exposure, thereby limiting their practical applicability. Herein, three strategies to enhance the adhesion of ruthenium films deposited on AISI 304 L by radio frequency (RF) magnetron sputtering, are investigated. These include roughening substrate surface, pulsing deposition pressure and using a 2 nm thick titanium seed layer. The ruthenium films produced by pulsing deposition pressure between 1.2 and 3.6 × 10−3 mbar exhibited the best performance, remaining mostly intact and adherent for 48 h of exposure to 1 M sulphuric acid. Resistance to electron transfer as measured by electrochemical impedance spectroscopy (EIS) was outstandingly high on these ruthenium films, giving corrosion protection efficiencies >500%. Scanning electron microscopy results show that pulsing deposition pressure significantly reduced tendency of film wrinkling, suggesting a considerable decrease in film stresses. A first of its kind, this study suggests two methods for improving the adhesion of ruthenium films on stainless steel substrates, thereby presenting an opportunity to expand the application spectrum of ruthenium.

Study of the influence of wire metals on dissimilar welds

The aim of this study is to investigate the effect wire metal on microstructure and mechanical properties of dissimilar welds between HSLA-X70 high strength steel alloy and 304L austenitic stainless steel produced by automatic tungsten arc welding (TIG). The weld joints were prepared using E304L, E316L, E2209L, and E7010 wire metal. The mechanical characteristics obtained from hardness, tensile and impact testing, were correlated to the optical and SEM microscopy, to establish a relationship between wire metal composition and the microstructures in different weld regions. It is concluded that E2209 wire metal lead to improve in the resilience characteristics and tenacity with a slight reduction in the ultimate tensile strength and hardness.

Study of the Corrosion of the Nickel-titanium Orthodontics Archwires in the Mouth

Objective: The corrosion behavior of titanium alloy (NiTi) orthodontic wires shows a high resistance to corrosion in various solutions, such as Ringer's solution, artificial saliva, sodium chloride solution, and others. In these different liquids, NiTi corrosion resistance is higher than that of stainless steel or cobalt-based alloys. These research studies the behavior of the nickel-titanium Orthodontics archwires in the mouth by three methods. Methods: The first testing was the SEM that can perform EPMA (Electro Probing Micro Analysis), microanalysis X, and local and quantitative elementary analysis, and the examination of NiTi are observed in two ways: cross sectional and surface examination. The second one was the electrochemical analysis performed by immersion in an artificial saliva solution consisting of lactic acid at 0.1 moles per liter and sodium chloride at 0.1 mole per liter: Two types of NiTi orthodontic arches were tested. The first ones are from the manufacturer Ortho Classic and were used in the mouth for 4-6 weeks. The second arches are from the manufacturer AZ Dent and were new. The last test was the TEM cartography that shows the atoms and their dispersion on the surface of the wire. Results: The results showed that the presence of corrosion cells in the artificial saliva proved that the NiTi orthodontic archwires were able to initiate the process of corrosion in the mouth, particularly at the point of friction in contact with the braces (Ti6Al4V). Conclusion: The results obtained by the MET on thin sections of orthodontic arches prepared by the FIB method revealed the presence of double or multiple layers of titanium oxide and N-oxide plus aluminum.

A Review of Modeling and Structural Analysis of Connecting Rod by using CATIA and ANSYS

The connecting rod is an important part of the IC motor as it transmits the movement of the piston to the drive shaft and converts the piston-turning motion into a rotating motion and vice versa. From the application point of view, it is essential that the connecting rod be lightweight and of good strength under fatigue or reverse loading. For this purpose in general the connecting rod material is carbon steel from aluminum alloy. Choosing a connecting rod for good engine performance is very difficult. The material used in the connecting rod must be chosen wisely because during the manufacturing process it must undergo various production processes and subsequent heat treatment process, which is very important for strength and toughness. Accordingly, the connecting rod made of high-strength carbon fiber will be compared with the connecting rod composed of stainless steel and aluminum alloy. The results can be used to improve weight reduction and to modify the linkage design. Keywords- Connecting Rod, Catia, ANSYS Workbench

Tribological and adhesion properties of microwave-assisted borided AISI 316L steel

Abstract In this study, AISI 316L stainless steel alloy samples were borided with powder-pack boriding method using Ekabor II powder with the support of a microwave furnace with a power of 2.9 KW and a frequency of 2.45 GHz. Boriding was carried out at 850, 900 and 950 °C temperatures for 2, 4 and 6 h of operation. A distinct diffusion barrier consisting of Fe–Ni–Si elements was detected in borided samples at 950 °C for 4 and 6 h. As a result of the Daimler Benz Rockwell-C adhesion tests, regions with insufficient adhesion strength were detected in these samples. In other samples, adhesion qualities between boride layers and substrate were in the range of HF1–HF3. The lowest specific wear rates were determined as 5.208 (mm3 Nm−1) × 10−6 and 5.210 (mm3 Nm−1) × 10−6 for the samples borided for 6 h at 850 °C and 4 h at 900 °C, respectively. It was determined that the increase in thickness of the brittle FeB compound increased the wear with the three-body abrasive wear mechanism.

Corrosion behaviour of lean duplex stainless steel in advanced oxidation process (AOP) based wastewater treatment plants

The corrosion of lean duplex stainless steel alloys is examined when applied as a construction material in advanced oxidation processes. Both electrochemical and immersion experiments have been carried out when subjecting wastewater to ozone or Fenton oxidation. The electrochemical experiments suggest that the presence of dissolved ozone at the levels tested does not result in an increased pitting susceptibility for none of the alloys included in the research. However, the application of Fenton reagents induces pitting corrosion to the studied lean duplex alloys. The immersion experiments highlight that crevice corrosion occurs during wastewater treatment with both ozone and Fenton reagents.

Localized Corrosion in Additively Manufactured Stainless Steel and Aluminum Alloys

Localized Corrosion in Additively Manufactured Stainless Steel and Aluminum Alloys

Influence of Surface Treatment on the Pitting Corrosion Behaviour of High Alloyed Stainless Steels in a Chloride Solution

Abstract The pitting corrosion behaviour of the austenitic stainless steel alloys 31 and A 351 with different surface treatments in a technical MgCl2 solution was investigated. Potentiometric current density-potential measurements were carried out, and critical repassivation temperatures were determined, using a galvanometric method. Pickled, ground, abrasively blast cleaned and shot-peened surfaces, respectively, were analysed concerning roughness, residual stress, work hardening and near-surface structure. The effects of the surface properties on the local corrosion behaviour was investigated. Basically, with increasing roughness, amount of residual stress and work hardening, one can see a tendency to decreasing resistance against pitting corrosion. On the other hand, those effects are superimposed by special properties of the passive layer, e. g., caused by pickling, or from the processing-specific surface texture.

Effect of process parameters on density and mechanical behaviour of a selective laser melted 17-4PH stainless steel alloy

Abstract 17-4 PH stainless steel alloy has been widely used in the field of defence industry such as weapon equipment, aerospace, nuclear energy, and so on because of its high strength, high toughness, high temperature resistance, and corrosion resistance. In order to meet the flexible manufacturing requirements of multi-variety small batch complex structure products with lower cost and higher efficiency, selective laser-melted 17-4PH stainless steel alloy has become the focus of research in the field of rapid alloy manufacturing in recent years. In this article, the density characteristics and the distribution characteristics of holes and spheroidization phenomena of 17-4 PH pre-alloyed powder subjected to multidimensional temperature conduction under selective laser melting are studied, and the mechanism of defect generation under temperature conduction is proposed. Finally, the optimal selection of the combination of different process parameters was carried out by orthogonal test, and it was found that the comprehensive mechanical behaviour of the 17-4 PH stainless steel alloy after being formed exceeded the ASTM A564 standard (the yield strength is 1,132 MPa, the tensile strength is 1,323 MPa, and the elongation is 16.6%).

Toxicological Assessment of an Acrylic Removable Orthodontic Appliance Using 2D and 3D In Vitro Methods.

Malocclusion is a global health problem, mainly affecting children and adolescents. For this reason, orthodontic treatment must be, on the one hand, safe, non-toxic, and effective and, on the other hand, it must have the best possible esthetic profile. Thus, the use of orthodontic appliances is addressed to all age groups, including young children, for a long period of time, which is why their safety profile is a matter of real interest. For this reason, the purpose of the present study was to evaluate the safety and biocompatibility of an acrylic removable orthodontic appliance made of polymethylmethacrylate and stainless steel alloy made by our team of researchers. To verify the biocompatibility of the medical device, it was immersed in artificial saliva with three different pHs (3, 7, and 10) for a period of ten days. Subsequently, the three types of saliva were tested on human keratinocytes (HaCaT cell line) in terms of viability and modification of cell morphology. Finally, the use of 3D reconstructed human epidermis verified the cytotoxic and irritating potential of the medical device, thus providing relevant information regarding its biocompatibility. The results revealed that by maintaining the orthodontic device in the saliva there is no release of substances with a toxic effect on the human keratinocytes and on the 3D reconstructed human epidermis. There were also no significant changes in cell morphology. In conclusion, it is suggested that the acrylic removable appliance has a safety profile recommended for in vivo use.

Crystalline characteristics of a dual-phase precipitation hardening stainless steel in quenched solid solution and aging treatments

This study investigated the development of the microstructures and aging reactions in a new dual-phase (allotriomorphic δ + γ) 17–4 precipitation-hardened (PH) stainless steel (SS) alloy. The 17–4 PH alloy, a martensitic stainless steel containing Cu (3–5 wt.%), was subjected to solid solution treatment followed by quenching using oil, H2O, or liquid N2. The microstructures of the steel specimens were primarily composed of lath martensite and allotriomorphic δ-ferrite. X-ray diffraction analysis indicated that the structures consisted entirely of bcc phase peaks. During aging at 560 and 600 °C, the local microstrain was released because of the tempering of the lath martensite and the formation of reverted austenite, resulting in a shift in the kernel's average misorientation distribution toward lower angles. The misorientation associated with the martensite boundaries ranged from 10° to 20° and from 47° to 57° in the packets. In the blocks, it ranged from 50° to 60°. The F1-ferrite approximately followed the Kurdjumov–Sachs orientation relationship with A1-austenite and A2-austenite.

Dimensionless parameters to define process windows of selective laser melting process to fabricate three-dimensional metal structures

Despite the intense research attention on the three-dimensional printing of metal structures via selective laser melting, a unified understanding of thermal conditions, and more specifically the input energy levels, necessary for minimizing macroscopic-defect generation is still lacking. Although simple and widely used parameters, such as linear or volumetric energy density, can be utilized to represent the characteristic energy level of the process, notable differences in printed morphologies and microstructures are observed in structures fabricated at the same energy density. Consequently, designing a process in terms of laser power and scan speed is largely based on trial-and-error approaches. In this work, based on the dimensional analysis of reported experimental data and numerical computation, the process windows suitable for the fabrication of single tracks were examined for various metals. In addition to the normalized enthalpy that quantifies the input energy level, another dimensionless parameter which measures the thermal penetration depth relative to the thickness of powder layer was found to be critical in defining the process window that resulted in acceptable single-track structure formation. To confirm the validity of the analysis, via the elimination of uncertainties and ambiguities inherent to the empirical data, numerical computations were conducted for single-track fabrications using Ti–6Al–4 V and 316L stainless steel alloys. The results of the numerical simulations showed good agreement with the findings obtained from the empirical data.

Carbide formation accompanying internal nitridation of austenitic stainless steel

Internal oxidation, carburization, and nitridation are three forms of internal corrosion commonly experienced by high-temperature alloy components in industrial plants. They are characterized by ingress of an oxidizing species (oxygen, carbon or nitrogen) into the sub-surface region of the affected material, often accompanied by formation of precipitate phases. These microstructural changes can have a significant impact on mechanical performance. Management of such threats to equipment integrity therefore requires a comprehensive understanding of microstructural evolution, including rate information. In this work, we use optical, scanning electron, transmission electron, and atomic force microscopy to study precipitate phases and quantify internal corrosion rates in the austenitic stainless steel Alloy 800H subjected to nitriding in a 95% N 2 + 5% H 2 atmosphere at service-relevant temperatures (800–1000 °C). We identify and characterize carbide and carbonitride precipitates formed alongside the expected nitrides, and use the thermodynamic software Thermo-Calc to show that formation of carbides during nitridation is thermodynamically possible in this alloy. This work ultimately demonstrates that a wide-ranging analytical approach may be crucial to gaining a full picture of the effects of internal corrosion in complex industrial alloys. • M 23 C 6 carbides form during nitridation of Alloy 800H stainless steel at 800–1000 °C. • Both experiment and thermodynamic calculations needed to characterize phenomenon. • Carbide penetration kinetics during nitridation at 800–1000 °C have been quantified. • Classical oxidation theory can predict penetration in lieu of experimental data.

Numerical simulation and experimental investigation: Metal spinning process of stepped thin-walled cylindrical workpiece

Many equipment and devices utilized in the aerospace industry are formed as symmetric parts through high plastic deformation of high strength sheet metal alloys with low thickness. Considering the inherent advantages of the spinning process of simple tooling and concentrated deformation loading, this process can be considered as one of the main options in producing these thin-sectioned lightweight parts. In this study, a Finite Element (FE) model has been developed to simulate the formation of a stepped thin-walled cylindrical workpiece of AISI 316 stainless steel alloy by spinning process. The FE simulation results were employed to investigate the effects of process parameters, including feed rate of the roller and rotational velocity of the mandrel on the distribution of stress and strain in the sheet metal, wrinkling failure, and thinning of the sheet metal during deformation. Experiments were carried out using selective input parameters based on the results of FE simulations. The comparison between FE simulations and experiments revealed that the developed model could predict the thinning of the sheet metals with over 93 % accuracy. Additionally, a good agreement between the experimentally deformed sheet configurations with those resulting from finite element simulations has been observed.

Effect of Cr on the microstructure and mechanical properties of diffusion-bonded Mo-Re alloy and 316L stainless steel

In this study, we reported a Cr effect as an interlayer on the mechanical properties and interfacial morphologies between Mo-14Re and 316L stainless steel for a steady solid-state bonding. The maximum tensile strength of the joint is 318 MPa at 1100 °C welding temperature, while all samples present a brittle fracture. In typical joints, fractures are along the Mo-14Re/Cr interface, and the domain fracture is Mo-Cr solid morphology. At a higher welding temperature, the interdiffusion of atoms become more sufficient, leading to a change in the lattice structure of solid solution that affect the mechanical properties of the bonded joints.

The Effect of the Substrate on the Microstructure and Tribological Properties of Cold Sprayed (Cr3C2-25(Ni20Cr))-(Ni-graphite) Cermet Coatings.

In this work, the effect of the substrate, Al 7075 alloy and 1H18NT9 stainless steel, on the microstructure and tribological properties of cold sprayed (Cr3C2-25(Ni20Cr))-(Ni-graphite) coatings was investigated. Both coatings were dense and did not reveal any discontinuities at the interfaces. They had similar Cr3C2 and graphite contents. Their microstructures showed a variety of grain sizes of the matrix phase between the inner part of the splat, showing large ones, and their boundaries, where elongated and nanostructured grains were formed during the deposition process. The coating deposited on the steel substrate revealed a slightly higher hardness and lower abrasive wear with the Al2O3 loose abrasive particles. The force required to destroy the durability of the coating–steel substrate system in the three-point bending test was higher than those of the other ones. The cermet deposit cold sprayed on steel and examined at 25 °C under 10 N revealed the best wear resistance and the lowest friction coefficient.

Stress Corrosion Cracking in Austenitic Stainless Steels in Reactor Primary Water–High Purity Oxidizing and in Supercritical Conditions

Abstract Austenitic stainless steels (SS) commonly used in the primary circuit of light water reactors (LWRs) have excellent corrosion resistance in demineralized (DM) water at high temperature (290°C–330°C) and pressure (7.4 MPa for boiling water reactor [BWR], 16 MPa for pressurized water reactor [PWR]). Radiolysis of primary DM water in BWR forms 200–300 ppb of oxidizing species (normal water chemistry [NWC]), which elevates the electrochemical potential of the SS from −300 to −600 mVSHE (mV with standard hydrogen electrode) when dissolved oxygen is 10–20 ppb to +100 to +200 mVSHE. Neutron irradiation of SS further induces metallurgical and microstructural changes, which compromises corrosion resistance. Thus, radiation makes BWR (NWC) environment hostile, causing extensive irradiation-assisted stress corrosion cracking (same as intergranular stress corrosion cracking [IGSCC]) in austenitic SS. IGSCC occurs in both sensitized (grain boundary chromium depletion) and nonsensitized conditions (strain-hardened region in base metal immediately adjacent to the weld fusion zone) and is a generic problem. IGSCC in BWR can be mitigated by hydrogen addition in water (hydrogen water chemistry [HWC]). BWR-HWC has limitations and is ineffective where boiling occurs. IGSCC of SS in PWR is limited because hydrogen addition in primary water suppresses radiolysis though the formation of aggressive environment in low-flow occluded regions can cause IGSCC in SS. Increasing demand for economic power has led to the primary environment in nuclear reactors to become hostile. Conceptual supercritical water reactor (SCWR) will use DM water at 500°C–600°C and 25 MPa, which is extreme for conventional LWR materials. IGSCC in austenitic SS and nickel-based alloys occurs in both oxidizing and reducing SCWR conditions, which can be further exacerbated by radiation. This article reviews how benign primary DM water becomes hostile in LWRs and extreme in SCWR conditions, causing SCC to be a generic problem in austenitic alloys.