Preparation and characterization of sol-gel derived yttria doped zirconia coatings on AISI 316L

A stable 4 mol% yttria-stabilized zirconia (YSZ) sol has been synthesized for coating stainless steel AISI 316L for biomedical applications. The sol was prepared by controlled hydrolysis of zirconium n-butoxide using acetylacetone and nitric acid as chelating agent and catalyst, respectively. X-ray diffractograms of calcined YSZ xerogel indicated a tetragonal structure at temperature as low as 400 °C. Stainless steel was dip-coated in transparent yellow YSZ sol followed by heat treatment between 400 and 600 °C for 2 h in air. A homogeneous and crack-free YSZ film was, thus, obtained on the stainless steel surface. Adhesion strength, measured by scratch test in progressive loading sequence on coated AISI 316L, showed 27 ± 3 N critical load. Corrosion performance of the surface coating was evaluated through open-circuit potential (OCP) measurement, impedance, polarization and chronoamperometry in Ringer's solution at 37 °C. The coating enhanced the pitting potential of the substrate. The metal ions released from AISI 316L was effectively controlled by the coating.     

Surface hardness improvement of plasma-sprayed AISI 316L stainless steel coating by low-temperature plasma carburizing

Low-temperature carburizing below 773 K of austenite stainless steel can produce expanded austenite, known as S-phase, where surface hardness is improved while corrosion resistance is retained. Plasma-sprayed austenitic AISI 316L stainless steel coatings were carburized at low temperatures to enhance wear resistance. Because the sprayed AISI 316L coatings include oxide layers synthesized in the air during the plasma spraying process, the oxide layers may restrict carbon diffusion. We found that the carbon content of the sprayed AISI 316L coatings by low-temperature carburizing was less than that of the AISI 316L steel plates; however, there was little difference in the thickness of the carburized layers. The Vickers hardness of the carburized AISI 316L spray coating was above 1000 HV and the amount of specific wear by dry sliding wear was improved by two orders of magnitude. We conclude that low-temperature plasma carburizing enabling the sprayed coatings to enhance the wear resistance to the level of carburized AISI 316L stainless steel plates. As for corrosion resistance in a 3.5 mass% NaCl solution, the carburized AISI 316L spray coating was slightly inferior to the as-sprayed AISI 316L coating.     

Evaluation of TiO2 coatings obtained using the sol–gel technique on surgical grade type 316L stainless steel in simulated body fluid

Gel titania is the titania which was prepared by hydrolysis of a titanium isopropoxide through a sol–gel process. A film of this titania was coated on surgical grade 316L stainless steel using a sol–gel dipping technique. The densified films at 700 °C in vacuum were characterized by X-ray diffraction and EDXA analysis for its crystallinity and purity. The content of the films were determined by FT–IR spectroscopy. The morphology of the coating was analyzed by SEM. The corrosion behavior of 316L SS samples coated with densified titania films were studied in simulated body fluid Ringer's solution by DC potentiodynamic polarization and AC impedance spectroscopic methods. The corrosion kinetic parameters show a considerable increase in the corrosion resistance for the coated steel samples in comparison to the pristine steel substrates.     

Characterization of electrophoretic chitosan coatings on stainless steel

Electrophoretic chitosan deposits on stainless steel AISI 316 L were produced and characterized. The coating quality (thickness, defectiveness, corrosion protection ability) was seen to depend on the electric field used for EPD. Corrosion studies in concentrated simulated body fluid (SBF5) demonstrated that the surface characteristics of AISI 316 L can be positively influenced by the chitosan coating.     

Microstructure and Corrosion Resistance of Dissimilar Weld-Joints between Duplex Stainless Steel 2205 and Austenitic Stainless Steel 316L

The microstructure and corrosion resistance of dissimilar weld-joints between stainless steel SAF 2205 and stainless steel AISI 316 L were investigated. Welding was accomplished by different types of welding wires AWS ER 347, AWS ER 316 L and AWS ER 309 L. To verify soundness of welded samples, nondestructive tests were performed. Metallographic samples were prepared from cross-section areas of weldjoints to investigate microstructure of different regions of weld-joints by optical microscopy and scanning electron microscopy. Corrosion resistance of weld-joints was evaluated in NaCl solution by potentiodynamic polarization and electrochemical impedance techniques. In the weld metal AWS ER 347, the brittle sigma phase was created, resulting in the decrease of weld-joint corrosion resistance. According to the results of metallurgical investigations and corrosion tests, welding wire AWS ER 309 L was suitable for welding duplex stainless steel(SAF 2205) to austenitic stainless steel(AISI 316L) by gas tungsten arc welding(GTAW)process.     

Advances in DLC coatings by hybrid PSII and PECVD as a barrier to corrosion in simulated body fluid*

In this study, diamond-like carbon (DLC) films were deposited on biomedical AISI316L stainless steel by hybrid plasma source ion implantation (PSII) and plasma-enhanced chemical vapour deposition (PECVD). Potentiodynamic polarization tests and Electrochemical Impedance Spectroscopy (EIS) have been employed to investigate the corrosion performance of different DLC films in Tyrode's simulated body fluid (pH = 7.4). The corrosion resistance of the DLC films by PECVD deteriorated rapidly after 24 h of immersion, but those made by hybrid PSII and PECVD offered more effective barrier for AISI316L stainless steel during 72 h of immersion. The test results demonstrated that the DLC film by hybrid PSII and PECVD possessed less corrosion current density, greater corrosion resistance, and more positive breakdown potential in simulated body fluid.     

Surface interactions of a W-DLC-coated biomedical AISI 316L stainless steel in physiological solution

The corrosion stability of a W-DLC coated surgical AISI 316L stainless steel in Hanks’ solution has been evaluated. Particle induced X-ray emission (PIXE) measurements were performed to evaluate the incorporation of potentially bioactive elements from the physiological solution. The film structure was analyzed by X-ray diffractometry and micro-Raman spectroscopy. The wear behavior was assessed using the sphere-on-disc geometry. The in vitro biocompatibility of the W-DLC film was evaluated by cytotoxicity tests. The corrosion resistance of the stainless steel substrate decreased in the presence of the PVD layer. EIS measurements suggest that this behavior was closely related to the corrosion attack through the coating pores. PIXE measurements revealed the presence of Ca and P in the W-DLC film after immersion in Hanks’ solution. This result shows that the PIXE technique can be applied to identify and evaluate the incorporation of bioactive elements by W-DLC films. The film showed good wear resistance and biocompatibility.     

Corrosion resistance and hemocompatibility of multilayered Ti/TiN-coated surgical AISI 316L stainless steel

Ti/TiN-multilayered films were prepared on surgical AISI316L stainless steel by arc ion plating. The crystallographic orientation and surface morphology were studied using XRD and SEM. The corrosion resistance of the coated specimen was evaluated by open-circuit test and potentiodynamic polarization test. It was found that the multilayered Ti/TiN-coated specimen had a weaker tendency towards corrosion and higher corrosion resistance in simulated bodily fluid than the bare substrate and the TiN-coated specimen. Additionally, in vitro hemocompatibility of the multilayered film and AISI316L was evaluated by dynamic clotting time and platelet adhesion experiments. The results indicated that for the multilayered Ti/TiN-coated specimen, the clotting time was lengthened and the adhesion and mutual interaction of platelets on its surface was also restrained.     

奥氏体不锈钢离子渗碳后的腐蚀行为

为了提高奥氏体不锈钢零件的使用寿命,利用低温离子渗碳技术对AISI 316L奥氏体不锈钢进行了表面渗碳处理.用X射线衍射仪和光学显微镜分析了渗碳层的微观组织结构,用显微硬度计测试了渗碳层的硬度分布,通过电化学极化曲线测试技术和化学腐蚀试验研究了离子渗碳AISI 316L不锈钢的腐蚀行为.渗碳层为单相碳过饱和奥氏体固溶体,由此明显提高了AISI 316L不锈钢的抗腐蚀性能,渗碳层硬度梯度平缓,表面显微硬度高达900 HV.结果表明,奥氏体不锈钢低温离子渗碳处理不仅提高了其表面硬度,而且提高了不锈钢表面的耐腐蚀性能,从而提高了其使用寿命.     

Novel fluorapatite/niobium composite coating for metallic human body implants

This study's aim was to design and prepare a novel composite coating in order to improve the biocompatibility of the metallic implants. AISI 316L stainless steel (SS) was used as a substrate and a filler-matrix fluorapatite/niobium (FA/Nb) composite coating was performed on the substrate by using plasma-spray technique. XRD and SEM analyses were utilized to characterize the coatings. Electrochemical polarization tests were carried out in two types of physiological solutions in order to evaluate the corrosion behavior of the coated specimens as an indication of biocompatibility. The results indicated that the corrosion current density of the FA/Nb coated samples was much lower than the obtained values for the FA coated SS substrates. Obviously, the novel FA/Nb composite coating could improve the corrosion resistance and the biocompatibility of the SS implants.     

Effect of Surface Treatment and Metallic Coating on Corrosion Behavior and Biocompatibility of Surgical 316L Stainless Steel Implant

Surface engineering technology is a suitable method for coatings on the metal surfaces or performing surface modification treatment,which can improve corrosion resistance and biocompatibility of metals.In this research,corrosion behavior of Nb coating on H 2 SO 4 and HNO 3 treated AISI stainless steel 316L (SS) was evaluated.Nb coating was carried out using physical vapor deposition process on the SS.Characterization techniques including scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) technique were used to investigate the microstructure and morphology of the coated and treated SS.Electrochemical potentiodynamic tests were performed in two types of physiological solutions and compared with the pristine SS specimens.Cyclic polarization tests were performed to evaluate resistivity against pitting.Experimental results indicate that Nb coating and surface treatment of the SS had a positive effect on improvement of corrosion behavior.The decrease in corrosion current densities was significant for coated and treated specimens.The corrosion current density was much lower than the values obtained for pristine specimens.     

NaSCN溶液中耐腐蚀材料的选择

用失重法和电化学法研究了Ａ３钢化学镀镍层、ＡＴＳＩ３１６和ＡＩＳＩ３０４Ｌ不锈钢在ＮａＳＣＮ溶液中的腐蚀行为。结果表明，ＡＩＳ３１６不锈钢在ＮａＳＣＮＢ溶液中具有优良的耐蚀性。其成分中Ｍｏ能抑制点蚀。Ａ３钢Ｎｉ－Ｐ镀层在ＮａＳＣＮ溶液中可能取代不锈钢，但镀层针孔及缺陷问题有待解决。     

AISI 316L不锈钢表面沉积Ti掺杂金刚石薄膜及其性能

为了进一步评价医用材料AISI 316L不锈钢表面沉积掺杂Ti类金刚石薄膜的应用性能,采用离子束辅助沉积技术在AISI 316L不锈钢表面沉积了掺杂Ti类金刚石(DLC-Ti)薄膜.分别利用X射线衍射仪、扫描电子显微镜、摩擦磨损试验机、电化学工作站及纳米压痕仪对DLC-Ti薄膜的晶体结构,表面与截面形貌,摩擦磨损性能,电化学性能,硬度和弹性模量进行了表征.结果表明:DLC-Ti薄膜的摩擦系数超低(0.017～0.029)且未出现磨损,自腐蚀电位和点蚀电位相对于基体向正电位方向移动.DLC-Ti薄膜综合性能较好,在整形外科及刀具等应用方面具有很好的前景.     

Mitigation of chloride driven stress corrosion cracking susceptibility of 316L austenitic stainless steel using plasma sprayed TiO2 coating

The present study proposes a protective TiO₂ coating against chloride driven stress corrosion cracking problem of 316L austenitic stainless steel. To test the performance of the proposed coating, the severe chloride-based boiling magnesium chloride solution at 155 °C was chosen. For experimentation, the constant strain-based U-bend specimens were coated with TiO₂ using atmospheric plasma spray method. The results indicated higher resistance by TiO₂ coated specimens against stress corrosion cracking problem, while the bare specimens experienced severe damage in the boiling magnesium chloride solution under various strain loading configurations. The coating-electrolyte system of TiO₂ coated sample demonstrated over seven times higher resistance, eventually led to reduction in corrosion rate over fifteen times compared to the bare 316L stainless steel in the boiling magnesium chloride solution. This improved performance of the coated 316L stainless steel is attributed to inhibition of outward diffusion of iron-chromium-nickel in the corrosive environment and the high chemical stability of TiO₂.     

Rate dependent cyclic behavior simulation of cold worked AISI 316L stainless steel pipe member

This research aims to simulate rate-dependent cyclic behavior of cold worked AISI 316L stainless steel pipe member using a developed FE analysis program. A rate-dependent cyclic plasticity model for cold worked AISI 316L stainless steel is derived based on the monotonic and cyclic loading experiments within quasi-static and dynamic strain rate ranges. Validity of the FE simulation program is presented by comparing analytical results to experimental data. Cyclic behavior of cold worked AISI 316L stainless steel pipe member is clearly simulated as a function of loading rate.     

AES study of passive films formed on a type 316 austenitic stainless-steels in a stress field

The type AISI 316 stainless steel, in addition to the principal alloying elements chromium and nickel, contains 2.5–3.5% of molybdenum. This element is added to improve the mechanical properties and the pitting resistance of austenitic alloys. Concerning the Stress Corrosion Cracking (SCC) resistance of austenitic stainless steels, molybdenum additions to alloys have a variable effect: the effect is detrimental for small additions of Mo, and it is beneficial for the alloy containing more than 4% Mo. Thus the Mo concentration on passive film plays an important role on the SCC resistance of steels. On the other hand, in a previous investigation, it was shown that the composition of passive films formed on the stressed 302 alloy depended on the compressive or tensile nature of stresses. Consequently, the aim of the present work is to study the composition of passive films formed on 316 steel and the migration of molybdenum in a stress field. Thus, Auger electron spectroscopy spectra were recorded to determine the chemical composition of the passive films formed on both sides of the type AISI 316 stainless steel U-bend samples. The results obtained show that the behaviour of chromium and oxygen in passive films formed on 316 steel in the stress field was nearly similar to that formed on 302 steel. Concerning the molybdenum diffusion outwards the passive film formed on the 316 steel was reduced by either the tensile or compressive stress field.     

Electrochemical and analytical investigation of passive films formed on stainless steels in alkaline media

Passive films were grown in potentiodynamic mode, by cyclic voltammetry on AISI 316 and AISI 304 stainless steels. The composition of these films was investigated by X-ray photoelectron spectroscopy (XPS). The electrochemical behaviour and the chemical composition of the passive films formed by cyclic voltammetry were compared to those of films grown under natural conditions (by immersion at open circuit potential, OCP) in alkaline solutions simulating concrete. The study included the effect of pH of the electrolyte and the effect of the presence of chloride ions.The XPS results revealed important changes in the passive film composition, which becomes enriched in chromium and depleted in magnetite as the pH decreases. On the other hand, the presence of chlorides promotes a more oxidised passive layer. The XPS results also showed relevant differences on the composition of the oxide layers for the films formed under cyclic voltammetry and/or under OCP.     

Si3N4和52100钢对磨副材料对CrN薄膜干摩擦学行为的影响

利用阴极电弧离子镀技术在316L不锈钢基体上制备了CrN薄膜。采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、纳米压痕仪对CrN薄膜的形貌、成分和力学性能进行了表征。为了研究Si_3N_4和52100钢对磨副材料对CrN薄膜和316L不锈钢干摩擦行为的影响,在2N、5N、8N三种载荷下,将CrN薄膜和316L不锈钢基体与Si_3N_4陶瓷球和52100钢球分别进行了往复式滑动干摩擦实验。采用扫描电子显微镜观察了磨痕的微观形貌,并对CrN薄膜和316L不锈钢基体的磨损机制进行了分析。结果表明:CrN薄膜表面平整,缺陷较少;CrN薄膜的纳米硬度约为28GPa,弹性模量约为350GPa;与Si_3N_4陶瓷球相比,CrN薄膜与52100钢球摩擦时摩擦因数相对较小(保持在0.7左右)且更加稳定;316L不锈钢的摩擦因数远大于CrN薄膜且波动较大;对磨球为Si_3N_4陶瓷球时,CrN薄膜的主要磨损机制为磨粒磨损,伴有少量的氧化和黏着磨损,316L不锈钢的磨损机制主要为磨粒磨损和塑性变形,伴有少量的氧化和黏着磨损;对磨球为52100钢球时,CrN薄膜的主要磨损机制为黏着磨损,伴有少量的氧化,316L不锈钢的磨损机制主要为黏着磨损,伴有少量的氧化和磨粒磨损。CrN薄膜与两种对磨球的磨损量均小于316L不锈钢基体的磨损量,说明CrN薄膜有效提高了基体的耐磨性。     

Effect of bias voltage on the electrochemical properties of TiN coating for polymer electrolyte membrane fuel cell

The electrochemical properties of TiN film coated on AISI 316 stainless steel (SS) by the magnetron sputtering physical vapor deposition (PVD) were studied for application as a bipolar plate. The crystal structure and surface morphology of the coatings were examined by x-ray diffractometry (XRD) and atomic force microscopy (AFM), respectively. The corrosion behaviors of the TiN films were investigated by electrochemical methods, including potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) under + 600 mV_SCE application. The electrochemical behavior of the TiN coatings was enhanced with increasing bias voltage due to lower corrosion current density and higher R_ct values during an immersion time of 168 h. This result was attributed to the formation of crystalline-refined TiN(200) at high bias voltage, which increased the coating compactness and the protective efficiency, and decreased passive current density.     

Effect of porosity and density on the mechanical and microstructural properties of sintered 316L stainless steel implant materials

In this study, the microstructure and mechanical properties of sintered AISI 316L stainless steel implant materials produced by powder metallurgy (P/M) method were investigated as a function of porosity amount. AISI 316L stainless steel powders were cold-pressed with 800 MPa pressure and sintered at 1200 °C, 1250 °C and 1300 °C for 30 min in a nitrogen atmosphere. The mechanical properties of the 316L implant samples were determined by tensile, fatigue and microhardness tests. Metallographic studies such as pore formation, and fractured surface analyses were performed by Scanning Electron Microscopy (SEM) and Light Optical Microscopy (LOM). The results of this study indicate that, irregular pore formation tendencies increase with an increase in porosity (%). Furthermore, an increase in porosity was shown to decrease the mechanical properties of sintered AISI 316L stainless steel. Sintering temperature is important parameter in decreasing the porosity of P/M materials.