Anti-corrosion characteristics of nitride-coated AISI 316L stainless steel coronary stents

The corrosion resistance of TiN and TaN coatings deposited on AISI 316L stainless steel thread-coiled coronary stents by pulsed bias arc ion plating is evaluated by electrochemical methods in deaerated Tyrode's simulated body fluids (37 ± 1 °C). The free corrosion potential of the TaN-coated stents is found to be nobler than that of the TiN-coated and uncoated stents throughout most of the immersion time. The potentiodynamic polarization test results indicate that the TaN coatings offer better passivation stability and anti-breakdown performance. The longer-term 6-month immersion tests disclose slight localized corrosion on the surface of both coatings, but no film delamination or large area pitting can be observed indicating reasonably good corrosion resistance after the long period.     

Microstructural evolution in adiabatic shear localization in stainless steel

Shear bands were generated under prescribed and controlled conditions in an AISI 304L stainless steel (Fe–18%Cr–8%Ni). Hat-shaped specimens were deformed in a Hopkinson bar at strain rates of ca 10⁴ s⁻¹ and shear strains that could be varied between 1 and 100. Microstructural characterization was performed by electron backscattered diffraction (EBSD) with orientation imaging microscopy (OIM), and transmission electron microscopy (TEM). The shear-band thickness was ca 1–8 μm. This alloy with low-stacking fault energy deforms, at the imposed strain rates (outside of the shear band), by planar dislocations and stacking fault packets, twinning, and occasional martensitic phase transformations at twin-band intersections and regions of high plastic deformation. EBSD reveals gradual lattice rotations of the grains approaching the core of the band. A [110] fiber texture (with the [110] direction perpendicular to both shear direction and shear plane normal) develops both within the shear band and in the adjacent grains. The formation of this texture, under an imposed global simple shear, suggests that rotations take place concurrently with the shearing deformation. This can be explained by compatibility requirements between neighboring deforming regions. EBSD could not reveal the deformation features at large strains because their scale was below the resolution of this technique. TEM reveals a number of features that are interpreted in terms of the mechanisms of deformation and recovery/recrystallization postulated. They include the observation of grains with sizes in the nanocrystalline domain. The microstructural changes are described by an evolutionary model, leading from the initial grain size of 15 μm to the final submicronic (sub) grain size. Calculations are performed on the rotations of grain boundaries by grain-boundary diffusion, which is three orders of magnitude higher than bulk diffusion at the deformation temperatures. They indicate that the microstructural reorganization can take place within the deformation times of a few milliseconds. There is evidence that the unique microstructure is formed by rotational dynamic recrystallization. An amorphous region within the shear band is also observed and it is proposed that it is formed by a solid-state amorphization process; both the heating and cooling times within the band are extremely low and propitiate the retention of non-equilibrium structures.     

Microstructural transformations in stress relieved type 316 stainless steel weld metal

The heat treatment of Type 316L weld metal containing small amounts of ferrite results in the transformation of the ferrite to χ or σ phases after aging for only 3 hr at 850°C. The χ-phase transformation is associated with a transitional M₂₃C₆ carbide, whereas the σ-phase transforms directly from the ferrite.     

Corrosion characteristics of polyaniline-coated 316L stainless steel in sulphuric acid containing fluoride

The corrosion resistance of conducting polyaniline (PANi) coatings deposited on 316L stainless steel (316L SS) at various cycle numbers of cyclic voltammetry (2-, 3- and 4-cycles) by electro-polymerization in sulphuric acid solution containing fluoride was investigated by electrochemical techniques. The corrosion resistance of the 316L SS substrate was considerably improved by the PANi coating. The increase of the cycle number of cyclic voltammetry increased the thickness and enhanced the performance of the PANi coating due to low porosity.     

316L不锈钢管道焊接工艺

我公司承担了攀钢煤化公司回收Ⅱ期脱酸蒸氨装置改造工程 ,该工程大部分是要求耐酸耐碱腐蚀的不锈钢管道 ,材质为 316Ｌ。工程质量的好坏 ,将直接影响到生产的安全运行。因此 ,制定合理有效的不锈钢焊接工艺是关键。1　焊接工艺( 1)焊接方法。由于现场多数为不锈钢管道 ,且大小不一 ,根据不锈钢的焊接特点 ,尽可能减小热输入量 ,故采用手工电弧焊、氩弧焊两种方法 ,ｄ >15 9ｍｍ的采用氩弧焊打底 ,手工电弧焊盖面。ｄ≤15 9ｍｍ的全用氩弧焊。焊机采用手工电弧焊 /氩弧焊两用的ＷＳ7-4 0 0逆变式弧焊机。( 2 )焊接材料。奥氏体不锈钢是…     

Study of Ce-modified antibacterial 316L stainless steel

316L stainless steel is widely used for fashion jewelry, but it can carry a large number of bacteria and bring the risk of infection since the steel has no antimicrobial performance. In this paper, the effects of Ce on the antibacterial property, corrosion resistance and processability of 316L were studied by microscopic observation, thin- film adhering quantitative bacteriostasis, and electrochemical and mechanical tests. The results show that a trace of Ce can distribute uniformly in the matrix of 316L and slightly improve its corrosion resistance in artificial sweat. With an increase in Ce content, the Ce is prone to form clustering, which degrades the corrosion resistance and the processability. The Ce-containing 316L exhibits Hormesis effect against S. aureus. A small Ce addition stimulates the growth of S. aureus. As the Ce content increases, the modified 316L exhibits an improved antibacterial efficacy. The more Ce is added, the better antibacterial capability is achieved. Overall, if the 316L is modified with Ce alone, it is difficult to obtain the optimal combination of corrosion resistance, antibacterial performance and processability. In spite of that, 0.15 wt.%-0.20 wt.% Ce around is inferred to be the best trade-off.     

Microstructure instability in TiC-316L stainless steel cermets

Titanium carbide (TiC) based cermets are commonly used in wear and corrosion resistance applications. The microstructural evolution, and related compositional instability, of TiC-based cermets prepared with a 316-L stainless steel binder is described in the present work. Samples were fabricated using a simple vacuum melt-infiltration procedure, with 5 to 30 vol.% binder. Infiltration temperatures ranged from 1475 °C to 1550 °C, held for up to 240 min, typically resulting in sintered samples with densities in excess of 99% of theoretical. It is demonstrated that irregularly shaped grains (concave/hollow) can arise after sintering, especially at 1475 °C, which is discussed in terms of the ‘instability of the solid-liquid interface’ theory. It is demonstrated that a complex, multi-layer core-rim structure arose for the cermets, with accommodation of selected steel constituents into the rim of the TiC grains. In particular, it is shown that the Mo in the original 316-L stainless steel is essentially fully depleted from the metallic binder phase, forming a Mo-rich inner-rim layer on the TiC grain cores.     

316L不锈钢分离器现场焊接工艺

分析了316L不锈钢分离器的焊接性和焊接工艺特点,根据其特点制定其焊接工艺:采用焊条电弧焊填充、盖面,采用氩弧焊打底,焊条电弧焊选用WSE-315型焊机、焊条A022,氩弧焊采用TIG400型号焊机、焊丝H00Cr19Ni12Mo2Cu2,采用V形坡口,坡口角度70°。焊后进行接头检验,结果表明,焊接接头成形良好,无咬边、凹陷、气孔、夹渣等缺陷;力学性能指标良好;焊道熔合较好,熔深满足要求。     

Electropolishing of 316L stainless steel for anticorrosion passivation

316L stainless steel is deemed an indispensable material in the semiconductor industry. In many instances, the surface of the production equipment needs to be treated for low-corrosion passivation, good finish, weldability, and cleanliness. The process characteristics of electropolishing meet these requirements well. The current study investigates the effects of the major processing parameters on the anticorrosion performance and the surface roughness. The electrolyte with 10% water content and a ratio between H₂SO₄ and H₃PO₄ of 4 and 6 has been proven to be successful, showing no corrosion pitting points on the specimen surface. The electrolyte temperature of 85±10 °C and the electrical current density of 0.5 to 1.0 A/cm² are found to be optimal. The processing time beyond 3 to 5 min produces no further improvement. The addition of 10% glycerin provides a very fine surface (maximum roughness of 0.05 μm), while the anticorrosion performance is deteriorated. The results obtained are useful for the manufacture of the semiconductor equipment.     

316L不锈钢管A-TIG焊工艺

近年来A -TIG(ActiveFluxTIG)焊在焊接界受到了人们的广泛重视 ,它是在母材表面涂敷一层活性焊剂进行焊接 ,在焊接电流不变的情况下使焊接熔深大幅度增加 (1～ 3倍 ) [1 ] 。从A -TIG焊缝质量来看 ,其成形系数Φ =B/H (B为熔宽 ,H为熔深 )愈小表示焊缝愈深而窄 ,这意味着既能保证焊缝充分焊透 ,又使得焊缝宽度方向的无效加热区和热影响区范围缩小 ,从提高焊接生产效率、减少焊接变形和缓解热影响区恶化的角度上来看 ,都是非常有利的。目前 ,国内外多位学者都对A -TIG焊进行了深入的研究和试验 ,但大都集中在板的试验上 ,本文主要针…     

Intensified plasma-assisted nitriding of AISI 316L stainless steel

In the present study, processing of AISI 316L stainless steel (316ss) has been conducted by intensified plasma-assisted processing (IPAP). The processing parameters (bias voltage, current density, chamber pressure and substrate temperature) of IPAP have been varied in an effort to determine which conditions lead to the formation of a single-phase structure, ‘m’ phase, and evaluate the properties of this phase. The structural characteristics of the nitrided layers produced by IPAP have been investigated by X-ray diffraction analysis. Nanoindentation experiments have been performed over cross-section to determine hardness and elastic modulus profiles. Dry sliding wear and potentiodynamic aqueous corrosion experiments have been conducted to characterize 316ss nitrided by IPAP. IPAP has been successful in producing single-phase m with high hardness and in shorter processing time compared to diode plasma nitriding. The IPAP produced single-phase nitrided layer was found to possess higher hardness (fourfold increase over the unprocessed alloy), excellent wear and corrosion resistance.     

生物医用316L奥氏体不锈钢的形变组织

借助扫描电镜、电子背散射衍射和透射电镜组织观察,对生物医用奥氏体不锈钢316L的形变组织进行了多尺度深入研究,其工程应变量范围为2%~40%。结果表明,当应变>20%时,316L奥氏体不锈钢中的<001>和<111>取向平行于拉伸方向,即出现了大量的变形孪晶和马氏体。从微米尺度和纳米尺度对孪晶和马氏体相变做详细分析发现,形变首先诱发形成变形孪晶,由于孪晶界减小了位错平均自由程而引起位错塞积,进一步诱发马氏体的转变。随着变形量的增加出现了更多的孪晶和α-马氏体,马氏体相变的过程只有γ→α转变,α马氏体主要分布在孪晶界附近,特别是孪晶交叉的位置。其中,奥氏体基体和α-马氏体之间的取向关系为:[011]_γ//[011]_α,(420)_γ//(123)_α。     

316L奥氏体不锈钢的高温流变行为

为建立能准确描述316L不锈钢流动特性的本构模型并合理制定其热成形工艺参数,采用圆柱试样在Gleeble-3500热模拟试验机上对316L奥氏体不锈钢进行等温压缩变形试验,研究316L不锈钢在变形温度为900℃~1 100℃、应变速率为0.01s-1~2s-1条件下的流变行为,建立其热变形本构方程。结果表明,变形温度和应变速率对流变应力有明显影响,流变应力随变形温度升高而降低,随应变速率的增加而升高。建立了材料常数α,n,lnA,及应变激活能Q与应变之间的非线性关系;316L不锈钢的热变形行为可用包含Arrhenius项考虑应变、应变速率及温度影响的本构方程描述。通过相关系数r、平均相对误差(AARE)对本构方程的准确性进行分析,结果表明,该方程可以准确预测316L不锈钢的高温流变行为。     

Rapid debinding of 316L stainless steel injection moulded component

Wax-based binder system is widely used but they suffer from long debinding time and a tendency to slump or distort during debinding. This has been a major obstacle for the economic process for metal injection moulding (MIM). For improving the debinding process, two-step debinding process has been introduced. Gas-atomised 316L stainless steel powder was injection moulded using two types of multi-component binder system comprising (1) a major fraction of paraffin wax and a minor fraction of polyethylene (PE) and stearic acid (SA) as a lubricant, (2) a major fraction of polyethylene glycol (PEG) and a minor fraction of polymethyl methacrylate (PMMA) binder system. Debinding was carried out in two steps; first, the moulded part is immersed in heptane or distilled water at 60 °C to remove the major component of the binder and then heated to remove the remaining binder. The results show that no swelling or distortion was observed on the moulded specimens on both binder systems. Furthermore, the specimens had an adequate strength for handling even after solvent extraction. Large pore were formed from the surface to the interior of the debound part during solvent extraction, allowed easy escape of pyrolysis gases during thermal debinding. Thermal debinding with ramp heating at rates from 3 to 15 °C/min was found to be successful.     

6061铝合金/316L不锈钢CMT熔钎焊工艺

对1.5 mm厚6061铝合金和2 mm厚316L不锈钢进行搭接焊,所选焊丝为4043铝硅焊丝。运用扫描电镜、能谱仪、X射线衍射仪、显微硬度计及万能拉伸试验机研究了焊接工艺参数对焊缝成形及焊接接头界面组织与力学性能的影响。研究结果表明,焊接参数对焊接接头宏观形貌有显著的影响,钎焊界面处不可避免的生成以FeAl3,Fe2Al5为主的金属间化合物相。拉剪试样断裂于钎焊金属间化合物层处,金属间化合物层厚度过大或过小都会影响焊接接头抗剪强度,厚度为1.5 μm时试样抗剪强度最高可达50 MPa。     

316L不锈钢波纹管腐蚀失效分析

采用光学显微镜、场发射扫描电镜(FESEM)及EDS能谱仪、X射线衍射仪、硬度计等对腐蚀失效316L不锈钢波纹管显微组织、表面形貌、腐蚀前后的物相及显微硬度进行了分析。结果表明,腐蚀失效316L不锈钢波纹管显微组织中的相组成为奥氏体和少量的铁素体,铁素体相在使用过程中最先被腐蚀是造成316L不锈钢波纹管的耐蚀性能下降的主要原因。316L不锈钢波纹管腐蚀表面含有较多铁的氧化物和硫化物以及铝的氧化物,蚀坑深度达30.6μm。     

316L不锈钢焊接接头耐晶间腐蚀试验

根据316L不锈钢的焊接特点,开发了一种钨极氩弧焊背部免充气保护焊接工艺。对焊接接头进行了金相组织、草酸刻蚀试验和晶间腐蚀试验。试验结果表明:316L母材显微组织为纯奥氏体;316L热影响区靠母材一侧的显微组织为粗大的奥氏体晶粒,靠焊缝一侧为奥氏体基体上分布着铁素体;316L根部焊缝的显微组织为奥氏体基体上分布着铁素体。刻蚀试验结果表明:焊缝和热影响区处的刻蚀形貌均是沟槽连成一片。虽然没有通过草酸刻蚀试验,但是所有试样均通过了Cu-CuSO4-硫酸晶间腐蚀试验。因此,钨极氩弧焊背部免充气保护焊接工艺是成功的。     

Resistance microwelding of 316L stainless steel wire to block

Abstract

The excellent corrosion resistance of low carbon vacuum melted 316 stainless steel coupled with its non-magnetic properties makes it ideal for biomedical applications. The typical joint geometry for microcomponents, such as medical implants, includes joining of fine wire to a larger block. However, this type of joint has received little attention in the current literature. The present study was conducted to examine the microstructure and mechanical properties of low carbon vacuum melted 316 stainless steel wire welded to a larger block. Results revealed solid state bonding occurring at low currents, while fusion bonding occurred at higher currents. This was due to the highly asymmetrical heat generation resulting in almost complete melting of the wire before the initiation of interfacial melting. This is a distinctly different bonding mechanism compared to previous studies on crossed wire joints.     

Printability of 316 stainless steel

ABSTRACT

A printability database can help in the selection of a printing process-alloy combination to reduce, and in some cases avoid, common defects in printed parts. The extensive testing of parts is not a viable option for determining printability because printing processes are inherently slow and expensive. Here we evaluate printability of stainless steel 316 by evaluating its susceptibilities to residual stresses, distortion, composition change and lack of fusion defects for laser (DED-L) and arc (DED-GMA) based directed energy deposition and laser powder bed fusion (PBF-L) processes using well-tested mechanistic models. Among these three processes, DED-GMA makes printed parts of 316 stainless steels most susceptible to residual stresses and distortion. High depth of penetration during DED-GMA makes components least susceptible to lack of fusion defects. Loss of volatile alloying elements from the tiny pools in PBF-L makes deposits the most vulnerable to composition change.