In vitro study of role of trace amount of Cu release from Cu-bearing stainless steel targeting for reduction of in-stent restenosis

A novel 316L type Cu-bearing stainless steel was developed in present work, aiming at reducing the occurrence of the in-stent restenosis after implantations of coronary stents, through trace amount of Cu release from surface of the steel in body fluid. It was found that there was a trace amount of Cu released from the Cu-bearing steel in a simulated body fluid, with no cytotoxicity. All the in vitro experimental results proved that this Cu-bearing steel could not only inhibit the proliferation of vascular smooth muscle cells, reducing the formation of thrombosis, which are the main reasons for happening of the in-stent restenosis, but also promote the proliferation of vascular endothelial cells needed for the revascularization, showing that this novel steel is prospective to be a new material for manufacturing coronary stents with function of reducing the in-stent restenosis.     

In vitro study of platelet adhesion on medical nickel-free stainless steel surface

A new nickel-free austenitic stainless steel, named BIOSSN4, has been recently developed to avoid the sensitivity to Ni ions. In the present study, the blood compatibility of the nickel-free stainless steel was evaluated in vitro by the platelet-rich plasma adhesion test with comparison to 316L stainless steel. The result shows that the nickel-free stainless steel only causes less activation of platelets, which was indicated by their morphology and low spreading. The result suggests that the nickel-free stainless steel should have better blood compatibility compared with 316L stainless steel and, as a bio-material, it should have obvious advantage and potential applications.     

Microbial corrosion resistance of a novel Cu-bearing pipeline steel

Microbiologically influenced corrosion (MIC) is becoming a serious problem for buried pipelines. Developing environmentally friendly strategies for MIC control is increasingly urgent in oil/gas pipeline industry. Copper (Cu) in steels can not only provide aging precipitation strengthening, but also kill bacterium, offering a special biofunction to steels. Based on the chemical composition of traditional X80 pipeline steel, two Cu-bearing pipeline steels (1% Cu and 2% Cu) were fabricated in this study. The microstructure, mechanical properties and antibacterial property against sulphate-reducing bacteria (SRB) and Pseudomonas aeruginosa (P. aeruginosa) were studied. It was found that the novel pipeline steel alloyed by 1%Cu exhibited acicular ferrite microstructure with nano-sized Cu-rich precipitates distribution in the matrix, resulting in better mechanical properties than the traditional X80 steel, and showed good MIC resistance as well. The pitting corrosion resistance of 1% Cu steel in as-aged condition was significantly better than that of X80 steel. A possible antibacterial mechanism of the Cu-bearing pipeline steel was proposed.     

Study of copper precipitation behavior in a Cu-bearing austenitic antibacterial stainless steel

Copper (Cu) precipitation behavior in a type 304 Cu-bearing austenitic antibacterial stainless steel was studied by analyses of variations in micro-hardness, electrical resistivity, electrochemical impedance and lattice constant of the steel, complemented with transmission electron microscopy (TEM) observation, showing more or less changes on these properties of the steel with different aging time. It was found that both micro-hardness and electrical resistivity measurements were relatively sensitive and accurate to reflect the Cu precipitation behavior in the experimental steel, indicating the beginning and finishing points of the precipitation, which are more simple and effective to be used for development of the new type of antibacterial stainless steels.     

In vitro corrosion resistance of Lotus-type porous Ni-free stainless steels

The corrosion behavior of three kinds of austenitic high nitrogen Lotus-type porous Ni-free stainless steels was examined in acellular simulated body fluid solutions and compared with type AISI 316L stainless steel. The corrosion resistance was evaluated by electrochemical techniques, the analysis of released metal ions was performed by inductively coupled plasma mass spectrometry (ICP-MS) and the cytotoxicity was investigated in a culture of murine osteoblasts cells. Total immunity to localized corrosion in simulated body fluid (SBF) solutions was exhibited by Lotus-type porous Ni-free stainless steels, while Lotus-type porous AISI 316L showed very low pitting corrosion resistance evidenced by pitting corrosion at a very low breakdown potential. Additionally, Lotus-type porous Ni-free stainless steels showed a quite low metal ion release in SBF solutions. Furthermore, cell culture studies showed that the fabricated materials were non-cytotoxic to mouse osteoblasts cell line. On the basis of these results, it can be concluded that the investigated alloys are biocompatible and corrosion resistant and a promising material for biomedical applications.     

Enhanced resistance of 2205 Cu-bearing duplex stainless steel towards microbiologically influenced corrosion by marine aerobic Pseudomonas aeruginosa biofilms

An antibacterial 2205-Cu duplex stainless steel(DSS)was shown to inhibit the formation and growth of corrosive marine biofilms by direct contact with copper-rich phases and the release of Cu~(2+)ions from the2205-Cu DSS surface.In this work,the microbiologically influenced corrosion(MIC)resistance of 2205-Cu DSS in the presence of the corrosive marine bacterium Pseudomonas aeruginosa was investigated.The addition of copper improved the mechanical properties such as the yield strength,the tensile strength and the hardness of 2205 DSS.Electrochemical test results from linear polarization resistance(LPR),electrochemical impedance spectroscopy(EIS)and critical pitting temperature(CPT)measurements showed that 2205-Cu DSS possessed a larger polarization resistance(R_p),charge transfer resistance(R_(ct))and CPT values,indicating the excellent MIC resistance of 2205-Cu DSS against the corrosive P.aeruginosa biofilm.The live/dead staining results and the SEM images of biofilm confirmed the strong antibacterial ability of 2205-Cu DSS.The largest pit depth of 2205-Cu DSS was considerably smaller than that of 2205 DSS after 14 d in the presence of P.aeruginosa(2.2μm vs 12.5μm).2205-Cu DSS possessed a superior MIC resistance to regular 2205 DSS in the presence of aerobic P.aeruginosa.     

Antibacterial behavior and related mechanisms of martensitic Cu-bearing stainless steel evaluated by a mixed infection model of Escherichia coli and Staphylococcus aureus in vitro

Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)are the most typical pathogenic bacteria with a significantly high risk of bio-contamination,widely existing in hospital and public places.Recent studies on antibacterial materials and the related mechanisms have attracted more interests of researchers.However,the antibacterial behavior of materials is usually evaluated separately on the single bacterial strain,which is far from the practical condition.Actually,the interaction between the polymicrobial communities can promote the growing profile of bacteria,which may weaken the antibacterial effect of materials.In this work,a 420 copper-bearing martensitic stainless steel(420 CuSS)was studied with respect to its antibacterial activity and the underlying mechanism in a co-culturing infection model using both E.coli and S.au reus.Observed via plating and counting colony forming units(CFU),Cu releasing,and material characterization,420 CuSS was proved to present excellent antibacterial performance against the mixed bacteria with an approximately 99.4%of antibacterial rate.In addition,420 CuSS could effectively inhibit the biofilm formation on its surfaces,resulting from a synergistic antibacterial effect of Cu ions,Fe ions,reactive oxygen species(ROS),and proton consumption of bacteria.     

Study of the processing map and hot deformation behavior of a Cu-bearing 317LN austenitic stainless steel

The hot-working behavior of a Cu-bearing 317LN austenitic stainless steel (317LN–Cu) was investigated in the 950–1150 °C temperature and 0.01–10 s^− 1strain rate range, respectively. The effects of different deformation parameters and optimum hot-working window were respectively characterized through analyzing flow stress curves, constitutive equations, processing maps and microstructures. The critical strain for dynamic recrystallization (DRX) was determined by the inflection point on θ-σ and −∂θ/∂σ-σ curves. The peak stress was found to increase with decrease in temperature and increase in strain rate. Typical signs of DRX over a wide range of temperatures and strain rates were observed on the flow stress curves. The power dissipation maps in the strain range of 0.1–0.4 were basically similar, indicating the insignificant effect of strain on the power dissipation maps of 317LN–Cu. However, the instability maps showed strong strain sensitivity with increasing strain, which was attributed to the flow localization. The optimum hot-working window for 317LN–Cu was obtained in the temperature range 1100–1120 °C and strain rate range 0.01–0.018 s^− 1, with a peak efficiency of 38%. Microstructural analysis revealed fine and homogenized recrystallized grains in this domain.     

Ageing behavior of a Cu-bearing ultrahigh strength steel

On ageing at different temperatures a various combination of properties has been obtained for this Cu-bearing ultrahigh strength steel. A substantial increase in strength has been obtained at 450 °C, accompanied by a drop in percentage elongation, percentage reduction in area and toughness. At 550 °C temperature extensive -Cu precipitates have been observed. The increased strength value retained in the temperature range of 450–600 °C and a secondary hardening peak obtained at 600 °C is probably due to the formation of fine Mo carbide precipitates. The decrease in strength at 650 °C along with an increase in percentage elongation, percentage reduction in area and toughness is due to the coarsening of Cu particles and a partial recovery of matrix. At 700 °C most of the Cu precipitates become rod shaped and formation of fresh martensite with a dark contrast is observed at the lath boundaries.     

Intergranular corrosion resistance of nanostructured austenitic stainless steel

Nanostructured metals and alloys possess very high strength but exhibit limited plasticity. Enhancement of the strength/ductility balance is of prime importance to achieve wide industrial applications. However, post-deformation heat treatment, which is usually used to improve plasticity, can lead to a decrease in other properties. In the case of austenitic stainless steels, heat treatment in the range from 480 to 815 °C can increase their susceptibility to intergranular corrosion. The aim of the work reported in this paper was to determine if nanostructured austenitic stainless steel is susceptible to intergranular corrosion if heat treated for 1 h at 700 °C. Samples of 316LVM austenitic stainless steel were hydrostatically extruded, in a multi-step process with the total true strain of 1.84 to produce a uniform microstructure consisting of nanotwins. These nanotwins averaged 21 nm in width and 197 nm in length. Subsequent annealing at 700 °C produced a recrystallised structure of 68-nm-diameter nanograins. The heat treatment improved the ductility from 7.8 to 9.2 % while maintaining the ultimate tensile strength at the high level of 1485 MPa. Corrosion tests were performed in an aqueous solution consisting of 450 ml concentrated HNO₃ and 9 g NaF/dm³ (according to ASTM A262-77a). The evaluation of the corrosion resistance was based on transmission and scanning electron microscopic observation of the microstructure and chemical analyses. The results revealed that both the as-received and HE-processed samples are slightly susceptible to the intergranular corrosion after annealing at 700 °C for 1 h.     

类金刚石薄膜在不锈钢表面结合强度及耐腐蚀性研究

类金刚石(DLC)薄膜与不锈钢的结合强度是DLC薄膜应用于血管支架表面改性的关键技术问题.利用磁过滤阴极真空弧源沉积方法在316L不锈钢表面沉积DLC薄膜,研究沉积时基体偏压、薄膜厚度以及钛过渡层对DLC薄膜与基体结合强度的影响.研究结果表明,316L表面制备相同厚度的DLC薄膜,采用-1000V脉冲偏压制备的薄膜结合强度明显优于-80V直流偏压下制备的DLC薄膜;随着DLC薄膜厚度的增大,DLC薄膜与316L基体的结合力下降;316L不锈钢表面制备一层100nm的钛过渡层之后可以改善DLC薄膜的结合状况,并且经过20%的拉伸变形后,DLC薄膜完整,耐蚀性优于未表面处理的316L不锈钢.以上研究结果表明,磁过滤阴极真空弧源方法制备DLC薄膜与316L结合强度高,可以有效的提高316L的耐腐蚀性,是一种具有应用前景的血管支架表面改性方法.     

Electrochemical study of hydroxyapatite coatings on stainless steel substrates

Hydroxyapatite coatings were synthesized electrochemically onto stainless steel. In this study, the composition and morphology of the coatings changed with the deposition and sintering conditions. The electrolyte was kept close to the composition of simulated body fluid with an adjusted pH of 8.0. Deposition temperature affected the purity of the deposits with higher temperatures (65 °C) giving better coatings. The sintering techniques were also shown to affect the deposits, with x-ray diffraction patterns showing well-defined peaks for hydroxyapatite when sintering under vacuum conditions. Coating density and corrosion resistance was improved when applying a double-layer coating technique versus a single-layer. Grain sizes were 30 to 40 nm even after sintering of these coatings in air. The formed coatings were characterized by powder x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and x-ray photoelectron spectroscopy.     

不锈钢表面涂覆C-SiC涂层及其阻氢性能的研究

采用磁控溅射结合离子束混合技术在不锈钢基体上制备C-(50～90)％ SiC涂层,对涂层进行加热处理及氢离子注入.对各种条件下制备的涂层进行元素深度分布分析.结果表明,SiC组分含量高的涂层具有更好的阻氢性能,而C组分含量高的涂层与基体具有更好的结合性能,综合考虑今后在氚废物包装桶涂覆的实际使用工况来看,采用C-(75～85)％SiC作为涂层似乎更合适些.通过对涂层阻氢性能的分析发现,C-SiC涂层经加热处理后,涂层的阻氢能力得到进一步的提高,并且可以提高氢离子在涂层中的稳定性.     

Pitting corrosion resistance of laser surface alloyed 304 stainless steel

Abstract

The pitting corrosion resistance of AISI 304 stainless steel (SS), which was laser melted in both nitrogen and argon atmosphere, was studied using the potentiodynamic anodic polarisation method. An attempt was made to introduce nitrogen onto the surface layers by melting in nitrogen atmosphere and argon atmosphere using a continuous wave CO₂ laser as the heat source at a power output of 3·06 kW at the laser head. The pitting corrosion resistance was determined by measuring the critical pitting potential during anodic polarisation. Secondary ion mass spectrometry (SIMS) was carried out on the laser melted surface to characterise the chemical composition. It was found that the pitting corrosion resistance of 304 SS was improved when laser surface melting was carried out in argon and was improved further when melting was carried out in nitrogen atmosphere. However, the improvement in pitting corrosion resistance in laser melted material was observed only in the reabraded condition and the pitting corrosion resistance in the as melted condition was lower than for the unmelted 304 SS. The improvement in localised corrosion behaviour was attributed to the increase of nitrogen content which was incorporated onto the surface layer during laser surface melting and this was confirmed using SIMS.

MST/1530     

陶瓷颗粒添加对热喷涂不锈钢涂层耐蚀性的影响

采用超音速火焰喷涂(HVAF)方法成功制备出不同种类及粒度陶瓷颗粒复合的不锈钢涂层,系统研究陶瓷颗粒的种类及粒度对复合涂层的硬度、孔隙率与耐蚀性能的影响;通过扫描电子显微镜、全自动硬度计、Image Pro Plus软件以及电化学工作站等分析测试技术对不锈钢/陶瓷颗粒复合涂层的微观结构、硬度及腐蚀行为进行系统表征与分析.结果表明:粗粒径棕刚玉(Al2O3)复合的不锈钢涂层的孔隙率低(0.7863％)、硬度高(637HV0.1)且耐蚀性能优异,其自腐蚀电位为-454.14 mV、自腐蚀电流密度为22.208 mA·cm-2;细粒径碳化硅(SiC)复合的不锈钢涂层具有较高的硬度(600HV0.1)及较好的耐蚀性能,其自腐蚀电位为-463.68 mV、自腐蚀电流密度为23.738 mA·cm-2.     

Effect of aging on the corrosion resistance of 2101 lean duplex stainless steel

The microstructure and localized corrosion behavior of a 2101 lean duplex stainless steel aged at 700 °C were investigated. The results showed that changes in the microstructure of the duplex stainless steel, due to the formation of precipitates, affected its pitting corrosion resistance. The values of the pitting potential and the critical pitting temperature dropped drastically before aging time up to 30 min. The potentiostatic pitting corrosion measurement indicated more sensitive to the small amount of precipitates compared to the potentiodynamic test. Pitting nucleated mainly in the ferrite phase for the solution-annealed specimen, while the initiation of pitting corrosion for the aged specimen took place at Cr-depletion area around the precipitates, i.e. in the newly formed secondary austenite phase.     

Promising in vitro performances of a new nickel-free stainless steel

Stainless steel is a metallic alloy largely employed in orthopaedics. However, the presence in its composition of a high quantity of nickel, an agent known to trigger toxic and allergic responses, is cause for concern. In this study, we have investigated the in vitro biocompatibility of a new nickel-reduced stainless steel, namely Böhler P558, in comparison to the conventional stainless steel AISI 316L. The neutral red (NR) uptake and the amido black (AB) tests were performed on L929 fibroblasts and MG63 osteoblasts to assess the cytotoxicity, while cytogenetic effects were evaluated on CHOK1 cells by studying the frequency of Sister Chromatid Exchanges (SCE) and chromosomal aberrations. Ames test was used to detect the mutagenic activity. The expression of selected markers typical of differentiated osteoblasts, such as alkaline phosphatase activity (ALP), type I collagen (CICP) and osteocalcin (OC) production, were also monitored in MG63 cells cultured on the tested materials. Our results indicate the absence of significant cytotoxicity and genotoxicity for both test alloys. ALP, CICP and OC analyses confirmed that both materials support the expression of these phenotypic markers. Overall, these data show that this Ni-free alloy possesses good in vitro biocompatibility and could have a potential for orthopaedic applications.     

离子注入Nb不锈钢双极板的耐孔蚀性能研究

为了探索离子注入Nb不锈钢双极板在模拟质子交换膜燃料电池(PEMFC)中的性能,采用极化曲线、恒电位试验和电化学阻抗谱等方法研究了离子注入铌316不锈钢在PEMFC环境中耐孔蚀性能的影响.研究表明:模拟PEMFC环境中316不锈钢和离子注入铌316不锈钢试样均发生孔蚀;Nb离子的注入提高了抗孔蚀性能,且随着介质温度的升高,孔蚀倾向加剧.孔蚀的诱发是离子注入铌316不锈钢表面水解形成Nb(OH)+4,导致钝化膜局部溶解破坏所致.模拟PEMFC环境中316不锈钢表面注入铌层膜电阻Rcoat、电荷转移电阻Rct升高,而注入铌层的电容值Ccoat、双电层电容Cct下降,表明注入铌层成为高电阻、低电容的阻挡层,对基体起到良好的保护作用.     

Investigation of microbial corrosion inhibition of Cu-bearing 316L stainless steel in the presence of acid producing bacterium Acidithiobacillus caldus SM-1

Stainless steel(SS)has unsatisfied corrosion resistance in many aggressive environments,particularly under a low p H condition in the bioleaching industry.In this study,through surface analyses and electrochemical measurements,the corrosion resistance of a novel Cu-bearing 316L SS was evaluated in the presence of an acid-producing bacterium,Acidithiobacillus caldus SM-1 that was able to create an extremely acidic corrosive environment.The significantly enhanced anti-microbiologically-inducedcorrosion performance could be explained by the intracellular reactive oxygen species(ROS)and Fenton reaction on the Cu-bearing 316L SS.