Antibacterial Stainless Steel Research Articles

Surface Damage and Microstructure Evolution of Copper-Containing Antibacterial Stainless Steel During Quasi-In Situ Tensile Process

Surface Damage and Microstructure Evolution of Copper-Containing Antibacterial Stainless Steel During Quasi-In Situ Tensile Process

Effect of heat treatment on the microstructure and mechanical properties of laser melting deposition copper-containing antibacterial stainless steel

Heat treatment was conducted on copper-containing antibacterial stainless steel prepared by laser melting deposition (LMD) under three different strategies (Planar, serpentine, chessboard), and its effect on microstructure and mechanical properties was studied.. Solid solution treatment at 1050 °C-15 min and aging treatment at 800 °C-6 h/12 h were applied to achieve antibacterial properties in the steel. The results show that the LMD-based stainless steel specimens have an interlocking fish scale shape, with cellular crystals in the melt pool and columnar crystals with different growth directions at the boundaries. After heat treatment, the results show that the fish scale melt pool boundary gradually becomes shallower, and the grain transitions to equiaxed crystal. Moreover, the fracture surface after stretching exhibits uniform equiaxed dimples, indicating ductile fracture. LMDed specimens to have high strength but poor toughness. After solid solution treatment, the strength decreased by about 24 %, and the toughness increased by 25.98 %. After the aging treatment, the second phase strengthening effect of the copper-rich stage made the material stronger and higher. In short, after heat treatment, component segregation is eliminated, the structure is more uniform, and the overall performance of the material is improved.

Physical metallurgy guided machine learning to predict hot deformation mechanism of stainless steel

This study proposes a novel approach to address the limitations of traditional experimental and mathematical statistical methods in predicting the deformation mechanism of materials. Specifically, a physical metallurgy-guided machine learning method is proposed to achieve fast and accurate prediction of the thermal deformation mechanisms of antibacterial stainless steels with varying Cu contents. First, the Arrhenius and the dynamic recrystallization model were developed utilizing experimental data for the preliminary prediction of the effect of Cu content on the thermal deformation behavior of antibacterial stainless steel. Then, the calculated intermediate parameters were incorporated into the original data set as additional input features to construct a physical metallurgy (PM) guided least squares support vector machine (LSSVM) prediction model, and the optimization of the prediction model is performed through utilization of a particle swarm optimization (PSO) algorithm. The results indicate that the addition of Cu content influences the rheological stress of antibacterial stainless steel at low temperatures and high strain rates. Furthermore, the increase of Cu content reduces the thermal deformation activation energy, inhibiting the dynamic recrystallization of antibacterial stainless steel, while an increase in deformation temperature or a decrease in strain rate promotes recrystallization. The proposed PM-PSO-LSSVM model is in good agreement with experiments, providing theoretical guidance for optimizing the composition and process parameters of antibacterial stainless steel.

Microbiologically influenced corrosion of a novel pipeline steel containing Cu and Cr elements in the presence of Desulfovibrio vulgaris Hildenborough

Inspired by the principle of copper-containing antibacterial stainless steel, a new type of Cu-Cr-bearing pipeline steel has been developed. Through a variety of surface characterization and electrochemical tests, the antibacterial property and microbiologically influenced corrosion resistance (MIC) of the novel type of steel were studied. Although the addition of Cu did not make this steel exhibit ideal antibacterial properties, all the results still showed that MIC resistance of the novel pipeline steel was better than that of X70 and Cr-bearing steels. The synergistic effect of Cr and Cu in the Cu-Cr-bearing pipeline steel contributed a beneficial effect to the improved MIC resistance.

A Novel Method for the Fabrication of Antibacterial Stainless Steel with Uniform Silver Dispersions by Silver Nanoparticle/Polyethyleneimine Composites.

Only a few studies have so far focused on the addition of silver to SS316L alloys by conventional sintering methods. Unfortunately, the metallurgical process of silver-containing antimicrobial SS is greatly limited due to the extremely low solubility of silver in iron and its tendency to precipitate at the grain boundaries, resulting in an inhomogeneous distribution of the antimicrobial phase and loss of antimicrobial properties. In this work, we present a novel approach to fabricate antibacterial stainless steel 316L by functional polyethyleneimine-glutaraldehyde copolymer (PEI-co-GA/Ag catalyst) composites. PEI is a highly branched cationic polymer, which makes it exhibit very good adhesion on the surface of the substrate. Unlike the effect of the conventional silver mirror reaction, the introduction of functional polymers can effectively improve the adhesion and distribution of Ag particles on the surface of 316LSS. It can be seen from the SEM images that a large number of silver particles are retained and well dispersed in 316LSS after sintering. PEI-co-GA/Ag 316LSS exhibits excellent antimicrobial properties and does not release free silver ions to affect the surrounding environment. Furthermore, the probable mechanism for the influence of the functional composites on the enhancement of adhesion is also proposed. The formation of a large number of hydrogen bonds and van der Waals forces, as well as the negative zeta potential of the 316LSS surface, can effectively enable the formation of a tight attraction between the Cu layer and the surface of 316LSS. These results meet our expectations of designing passive antimicrobial properties on the contact surface of medical devices.

Wear behavior of copper containing antibacterial stainless steel in different environmental media and EBSD analysis of its sub surface structure

Wear behavior of copper containing antibacterial stainless steel in different environmental media and EBSD analysis of its sub surface structure

Damage Evolution of Antibacterial Stainless Steel at Different Loading Rates Based on Digital Image Correlation Method

Using Shimadzu AGS‐100KN tensile machine, LEICA‐LM/DM optical microscope, and electron backscatter diffractometer (EBSD), combined with digital image correlation (DIC) analysis method, the damage evolution behavior of copper‐containing antibacterial stainless steel in large deformation area and small deformation area under different loading rates is investigated. The results show that with the increase of the loading rate, the temperature rise induces local adiabatic shear bands in the microstructure, increasing work hardening, and a decrease in ultimate stress and full elongation. The damage evolves in the large deformation area, the sample is mainly deformed rapidly, the grain deformation degree is large, and the deformation basically stops in the small deformation area. The damage factor of the specimens in the large deformation zone and the small deformation zone increases with the increase of strain, and the damage deformation rate and the critical damage factor decrease with the increase of the loading rate. Based on the DIC method, the damage evolution equations of copper‐containing antibacterial stainless steel samples in large and small deformation regions under different loading rates are established, which effectively reflect the damage evolution laws at different loading rates.

Research on Stamping Formability and Microstructure of Copper-Containing Antibacterial Stainless Steel

Research on Stamping Formability and Microstructure of Copper-Containing Antibacterial Stainless Steel

Manufacture of wear-resistant cast iron and copper-bearing antibacterial stainless steel from molten copper slag via vortex smelting reduction

A novel method of preparing wear-resistant cast iron and copper-bearing antibacterial stainless steel by moderate dilution of molten copper slag and vortex smelting reduction is proposed in this paper. The reduction behaviors of different components during vortex smelting reduction after medium dilution of molten copper slag are systematically investigated. Thermodynamic analysis results show that lime (CaO) can promote the decomposition of the iron peridotite phase and strengthen the reduction of copper and iron in slag. Under the conditions of 1450 °C, slag alkalinity of 1.0, 0.13 wt% carbon addition, vortex stirring speed of 250 rpm, and sedimentation stirring speed of 63 rpm, the metallization rate of copper and iron is 91.76%. In addition, 97.90 wt% zinc and 14.79 wt% lead in copper slag enter flue gas to be recovered, and 94.11 wt% silver and 88.66 wt% gold are reduced into metal. HBW555Cr13 wear-resistant cast iron and 20Cr13Cu3 copper-bearing martensitic antibacterial stainless steel, which meet the requirements of Chinese national standards, are successfully prepared by this process, realizing the separation, enrichment, and recovery of valuable components in the copper slag. The Brinell hardness of wear-resistant cast iron is 575, and the antibacterial rate of copper-containing antibacterial stainless steel against Escherichia coli is more than 99%. The reduction slag can be used as the raw material for preparing cement clinker after water quenching. There is no secondary waste residue, which realizes the molten copper slag's large-scale, slag-free, and high-value utilization.

Corrosion and antimicrobial behavior of stainless steel prepared by one-step electrodeposition of silver at the grain boundaries

Introducing Ag to the surface is a common means to obtain an antibacterial product. However, the poor adhesion between coating and substrate often results in a non-durable antibacterial performance. Herein, we developed a simple one-step pulse-reverse electrodeposition method to introduce Ag particles into the grain boundaries of 304 stainless steel (304 SS) surface for a stable and long-acting antibacterial application. In the present method, the grain boundary was preferentially corroded as the potential “seat” for Ag particles, and the surface content of Ag upgraded to 0.57 at.% by optimizing the electrolyte, electrodeposition temperature, reaction time, and current density. Without deteriorating the corrosion resistance of the substrate, the 304 SS with Ag particles demonstrated considerable antibacterial properties against Escherichia coli and Staphylococcus aureus even after ultrasonic treatment or accelerated abrasion. Consequently, the current study proposes a facile strategy for the production of durable antibacterial stainless steel.

High Temperature Tensile Fracture Behavior of Copper-Containing Austenitic Antibacterial Stainless Steel.

The mechanical properties and deformation microstructure of cast 304 Cu-containing austenitic stainless steel at 10−3/s strain rate in the range of 700~1200 °C were studied by Gleeble thermal simulator, metallographic microscope and scanning electron microscope. The results showed that the thermoplasticity of 304 Cu-containing austenitic stainless steel was higher than 60% when the temperature was higher than 1000 °C, and the tensile strength as a whole decreased with the increase in temperature. During the tensile process, the morphology and content of ferrite in the test steel were the main factors affecting the high-temperature thermoplastic of the billet. The inclusions near the fracture and the existence of ferrite at the grain boundary greatly affected the formation of microcracks and holes and the fracture.

Enhanced antibacterial behavior of a novel Cu-bearing high-entropy alloy.

Contact infection of bacteria and viruses has been a critical threat to human health. The worldwide outbreak of COVID-19 put forward urgent requirements for the research and development of the self-antibacterial materials, especially the antibacterial alloys. Based on the concept of high-entropy alloys, the present work designed and prepared a novel Co0.4FeCr0.9Cu0.3 antibacterial high-entropy alloy with superior antibacterial properties without intricate or rigorous annealing processes, which outperform the antibacterial stainless steels. The antibacterial tests presented a 99.97% antibacterial rate against Escherichia coli and a 99.96% antibacterial rate against Staphylococcus aureus after 24 h. In contrast, the classic antibacterial copper-bearing stainless steel only performed the 71.50% and 80.84% antibacterial rate, respectively. The results of the reactive oxygen species analysis indicated that the copper ion release and the immediate contact with copper-rich phase had a synergistic effect in enhancing antibacterial properties. Moreover, this alloy exhibited excellent corrosion resistance when compared with the classic antibacterial stainless steels, and the compression test indicated the yield strength of the alloy was 1015 MPa. These findings generate fresh insights into guiding the designs of structure-function-integrated antibacterial alloys.

Characterization of the copper rich phase precipitation behavior and comprehensive properties of austenitic stainless steel

Antibacterial austenitic stainless steel was nominated as a new biomaterial material. The copper rich phase precipitation behavior and comprehensive properties in copper-containing austenitic stainless steel after different aging treatment were systematically studied. It was found that a large number of dispersed copper rich phases developed at 750–800 °C. At 800 °C, copper rich phase precipitated quickly within 1 h, but grew and coarsened slowly in the later stage. The hardness of the material increased gradually with the precipitation of copper rich phase, until it reached the maximum after 6 h and tended to be stable. However, with the extension of aging time, high concentration of copper rich phase destroyed the passive film on the surface of stainless steel and accelerated the matrix corrosion, but promoted the release of copper ions and improved the antibacterial property. Therefore, the comprehensive experimental results indicated that 3.60% Cu-304L stainless steel treated by solid solution at 1050 °C for 5 min and aged at 800 °C for more than 6 h had good corrosion resistance and antibacterial property. These results could provide theoretical guidance for the optimal design of copper containing antibacterial stainless steel in production process.

Quantitative Evaluation of Nucleic Acid Degradability of Copper Alloy Surfaces and Its Correlation to Antibacterial Activity.

Copper (Cu) and its alloys have bactericidal activity known as “contact killing” with degradation of nucleic acids inside the bacteria, which is beneficial to inhibit horizontal gene transfer (HGF). In order to understand the nucleic acid degradability of Cu and its alloy surfaces, we developed a new in vitro method to quantitatively evaluate it by a swab method under a “dry” condition and compared it with that of commercially available antibacterial materials such as antibacterial stainless steel, pure silver, and antibacterial resins. As a result, only Cu and its alloys showed continuous degradation of nucleic acids for up to 6 h of contact time. The nucleic acid degradability levels of the Cu alloys and other antibacterial materials correlate to their antibacterial activities evaluated by a film method referring to JIS Z 2801:2012 for Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Nucleic acid degradation by copper (I) and (II) chlorides was confirmed at the ranges over 10 mM and 1–20 mM, respectively, suggesting that the copper ion release may be responsible for the degradation of the nucleic acids on Cu and its alloy surfaces. In conclusion, the higher Cu content in the alloys gave higher nucleic acid degradability and higher antibacterial activities.

Flow Stress Behavior and Microstructure Evolution of Austenitic Stainless Steel with Low Copper Content during Hot Compression Deformation

In order to study the microstructure evolution and flow stress behavior of as cast antibacterial austenitic stainless steel containing 1.52 wt.% copper, Gleeble 3800 was used for thermal compression simulation test. Through OM and EBSD analysis, it is found that the dynamic recrystallization mechanism of thermal deformation is mainly discontinuous dynamic recrystallization. With the increase of deformation temperature and deformation rate, the proportion of recrystallization nucleation gradually increases. The growth of twins relies on recrystallization and, at the same time, promotes dynamic recrystallization. Considering the influence of strain on flow stress, the strain compensation Arrhenius model is established according to the obtained stress-strain curve, and high accuracy is obtained. The correlation coefficient and average relative absolute error are 0.979 and 7.066% respectively. These results provide basic guidance for the technology of microstructure control and excellent mechanical properties of antibacterial stainless steel.

Morphology and Antibacterial Properties of Copper Precipitates in Ferrite Stainless Steel

The size of copper precipitates is the main factor affecting the antibacterial performance of antibacterial stainless steel. To study the mechanism of copper precipitate growth in ferritic stainless steel, the shape coefficient η and average specific interfacial energy of copper precipitate bar{sigma } were calculated. The growth process of copper precipitate was observed by atomic probe tomography and transmission electron microscope. The results show that the shape coefficient of copper precipitate was 3.053, and the average specific interfacial energy was bar{sigma } = 0.4832 - 0.1652 times 10^{ - 3} ,{text{T}}. The increase in the aging time resulted in an increase in the size of copper precipitates and a decrease in the number density. In addition, with the increase in the aspect ratio, the shape of the precipitated phase changed from an initial spherical shape to ellipsoid shape and finally to a rod shape. The increase in the annealing time enhanced the antibacterial activity of the tested steel until almost 100% of the bacteria were killed. Thus, the antibacterial performance is closely related to the size and total surface area per unit area of the precipitate.

The Initial Precipitation Behavior of Copper in Ferritic Stainless Steel

The precipitation of a suitable amount of Cu phase is the key to the antibacterial performance of Cu-containing antibacterial stainless steel. In order to study the precipitation behavior of Cu in ferritic stainless steel, the nucleation rate–temperature curve and phase transition kinetics curve of the Cu-rich phase were calculated theoretically. The distribution, size, and composition of Cu precipitates were characterized, and the distributions of Ni and Mn in the Cu precipitates at different annealing times were also analyzed by atom probe tomography and transmission electron microscopy. The crystal structure of the Cu precipitates was observed by high-resolution electron microscopy. With an increase in annealing temperature, the nucleation rate decreases and the time for nucleation of Cu precipitates increases monotonously. Accordingly, the size of the Cu-rich phase increases, and the number density decreases with increasing annealing time. Moreover, the contents of Ni and Mn gradually increase, and the Ni and Mn atoms aggregate on the surface of the Cu-rich phase. When the steel is annealed for 60 s, the Cu precipitate in the ferrite matrix exhibits a 9R structure with multiple twins.

The Effectiveness of Nafion-Coated Stainless Steel Surfaces for Inhibiting Bacillus Subtilis Biofilm Formation

Stainless steel is one of most commonly used materials in the world; however, biofilms on the surfaces of stainless steel cause many serious problems. In order to find effective methods of reducing bacterial adhesion to stainless steel, and to investigate the role of electrostatic effects during the formation of biofilms, this study used a stainless steel surface that was negatively charged by being coated with Nafion which was terminated by sulfonic groups. The results showed that the roughness of stainless steel discs coated with 1% Nafion was similar to an uncoated surface; however the hydrophobicity increased, and the Nafion-coated surface reduced the adhesion of Bacillus subtilis by 75% compared with uncoated surfaces. Therefore, a facile way to acquire antibacterial stainless steel was found, and it is proved that electrostatic effects have a significant influence on the formation of biofilms.

A study on the effect of ultrashort pulsed laser texturing on the microstructure and properties of metastable S phase layer formed on AISI 316L surfaces

Austenitic stainless steels (ASS) are an important material within the food and medical industries. However, their current limitations of poor wear resistance and susceptibility to bacterial colonisation have limited further uptake. Low-temperature plasma nitriding can address the poor durability of the ASS alloys by forming the S phase, therefore, providing combined improvement in hardness, wear resistance and corrosion resistance. Additionally, pulsed laser texturing can also be used to introduce functional antibacterial textures. However, due to the thermal nature of laser patterning and the thermodynamic metastability of the S phase, almost no research has been conducted thus far on combining the technologies.Therefore, this study for the first time has investigated the response of S phase treated surfaces to ultrashort (nano and femtosecond) laser texturing. The results have shown that, both theoretically and in practice, laser pulses within the nanosecond regime led to the damage of the surface, decomposition of the metastable S phase and loss of the corrosion resistance. In contrast, no change of the S phase surface layer could be detected following femtosecond laser texturing. Hence, demonstrating the feasibility of texturing S phase surfaces using femtosecond pulsed lasers, thus paving the way towards long-lasting multi-functional antibacterial stainless steel surfaces.

A Novel Design to Enhance the Mechanical Properties in Cu-Bearing Antibacterial Stainless Steel.

A novel method based on nano-scale precipitation hardening has been studied to strengthen copper-bearing ferrite antibacterial stainless steel. Bimodal precipitations can be observed after antibacterial annealing and low temperature aging treatment, which are large rod-shaped precipitates and nano-sized spherical precipitates, respectively. Due to two different morphological precipitates, the strength of the material is significantly improved without sacrificing formability, and at the same time, the excellent antibacterial properties remain. Under low temperature aging treatment, there is no obvious evidence to show the segregation at the interface between the rod-shaped copper precipitation and the matrix due to the low segregation coefficient of copper. The nano-sized copper precipitation uniformly nucleated and distributed on the matrix. The optimized heat treatment process is antibacterial annealing at 800 °C for half an hour followed by one-hour-aging treatment at 550 °C.