Studies of diamond-like carbon (DLC) films deposited on stainless steel substrate with Si/SiC intermediate layers

In this work, diamond-like carbon （DLC） films were deposited on stainless steel substrates with Si/SiC intermediate layers by combining plasma enhanced sputtering physical vapour deposition （PEUMS-PVD） and microwave electron cyclotron resonance plasma enhanced chemical vapour deposition （MW-ECRPECVD） techniques. The influence of substrate negative self-bias voltage and Si target power on the structure and nano-mechanical behaviour of the DLC films were investigated by Raman spectroscopy, nano-indentation, and the film structural morphology by atomic force microscopy （AFM）. With the increase of deposition bias voltage, the G band shifted to higher wave-number and the integrated intensity ratio ID/IG increased. We considered these as evidences for the development of graphitization in the films. As the substrate negative self-bias voltage increased, particle bombardment function was enhanced and the sp^3-bond carbon density reducing, resulted in the peak values of hardness （H） and elastic modulus （E）. Silicon addition promoted the formation of sp^3 bonding and reduced the hardness. The incorporated Si atoms substituted sp^2- bond carbon atoms in ring structures, which promoted the formation of sp^3-bond. The structural transition from C-C to C-Si bonds resulted in relaxation of the residual stress which led to the decrease of internal stress and hardness. The results of AFM indicated that the films was dense and homogeneous, the roughness of the films was decreased due to the increase of substrate negative self-bias voltage and the Si target power.

Experimental investigation of erosion rate for gas-solid two-phase flow in 304 stainless/L245 carbon steel

Erosion is one of the most concerning issues in pipeline flow assurance for the Oil&Gas pipeline industries,which can easily lead to wall thinning,perforation leakage,and other crucial safety risks to the steady operation of pipelines.In this research,a novel experimental device is designed to investigate the erosion characteristics of 304 stainless and L245 carbon steel in the gas-solid two-phase flow.Regarding the impacts on erosion rate,the typical factors such as gas velocity,impact angle,erosion time,particle material and target material are individually observed and comprehensive analyzed with the assistance of apparent morphology characterized via Scanning Electron Microscope.Experimental results show that the severest erosion occurs when the angle reaches approximate 30°whether eroded by type I or type II particles,which is observed in both two types of steel.Concretely,304 stainless steel and L245 carbon steel appear to be cut at low angles,and impacted at high angles to form erosion pits.In the steady operational state,the erosion rate is insensitive to the short erosion time and free from the influences caused by the“erosion latent period”.Based on the comparison between experimental data and numerical results generated by existing erosion models,a modified model with low tolerance(<3%),high feasibility and strong consistency is proposed to make an accurate prediction of the erosion in terms of two types of steel under various industrial conditions.

Effect of stabilizing elements Nb and Ti on the microstructure and properties of low carbon ferritic stainless steel

The effect of stabilizing elements, such as Nb and Ti, on the microstructure and properties of low carbon ferritic stainless steel （FSS） has been investigated. The results of the Thermo-calc simulation have shown that the interstitial elements, such as C and N, may be completely stabilized by the addition of Nb and Ti. With the increase of Nb and Ti contents ,the α ＋ γ two phases gradually transfer to a single α-phase under a high temperature condition ,and the content of the carbide M23 C6 gradually decreases. The microstructure has indicated that the combined addition of Nb and Ti can promote the recrystallization of the band structure and form more uniform equiaxed grains. Also, with the increase of Nb and Ti contents,the elongation, the r-value and the corrosion resistance of cold-rolled and annealed sheets are improved prominently. In comparison with the effect of Ti ,the addition of Nb is more beneficial to the increase of r-value and the corrosion resistance.

Conductive and corrosion behaviors of silver-doped carbon-coated stainless steel as PEMFC bipolar plates

Ni–Cr enrichment on stainless steel SS316 L resulting from chemical activation enabled the deposition of carbon by spraying a stable suspension of carbon nanoparticles; trace Ag was deposited in situ to prepare a thin continuous Ag-doped carbon film on a porous carbon-coated SS316 L substrate. The corrosion resistance of this film in 0.5 mol·L^（-1） H_2SO_4 solution containing 5 ppm F- at 80°C was investigated using polarization tests. The results showed that the surface treatment of the SS316 L strongly affected the adhesion of the carbon coating to the stainless steel. Compared to the bare SS316 L, the Ag-doped carbon-coated SS316 L bipolar plate was remarkably more stable in both the anode and cathode environments of proton exchange membrane fuel cell（PEMFC） and the interface contact resistance between the specimen and Toray 060 carbon paper was reduced from 333.0 m？·cm^2 to 21.6 m？·cm^2 at a compaction pressure of 1.2 MPa.

Electrochemical Investigation of Corrosion on AISI 316 Stainless Steel and AISI 1010 Carbon Steel: Study of the Behaviour of Imidazole and Benzimidazole as Corrosion Inhibitors

An electrochemical investigation of the corrosion on AISI 316 austenitic stainless steel and AISI 1010 carbon steel in sodium chloride solution (3.0 wt.%) was performed in the absence and presence of imidazole and benzimidazole corrosion inhibitors. The results showed that at any inhibitor concentration (25 ppm to 1000 ppm), there was an increase in the polarisation resistance of both steels. The highest efficiency of corrosion inhibition was obtained using imidazole at a concentration of 50 ppm for both steels, with values of 96% for the AISI 316 stainless steel and 73% for the AISI 1010 carbon steel.

Study on process of roll bonding stainless and carbon steel under non-vacuum condition

The non-vacuum roll bonding method of nickel plating on the base materials is put forward in accordance with the primary problems existed in the roll bonding of stainless/carbon steel. After nickel plating test on the base materials, the microstructure of nickel cladding is observed by scanning electron microscopy （SEM） at high, and room temperature, and the results show that the nickel cladding on base material can be protected from oxidation in the high temperature. Non-vacuum roll bonding tests of nickel plating on base materials are done by the roll bonding equipment, and the roll bonding plates of stainless/carbon steel are obtained. The microstructure and the elements distribution of non-vacuum roll bonding interface are analyzed by optical microscope （OM） and SEM. The results reflect that the nickel plating layer and the base materials bond well.

Advanced manufacturing technologies of large martensitic stainless steel castings with ultra low carbon and high cleanliness

The key manufacturing technologies associated with composition, microstructure, mechanical properties, casting quality and key process control for large martensitic stainless steel castings are involved in this paper. The achievements fully satisfeid the technical requirements of the large 700 MW stainless steel hydraulic turbine runner for the Three Gorges Hydropower Station, and become the major technical support for the design and manufacture of the largest 700 MW hydraulic turbine generator unit in the world developed through our own efforts. The characteristics of a new high yield to tensile strength (R p0.2/R m ) ratio and high obdurability martensitic stainless steel with ultra low carbon and high cleanliness are also described. Over the next ten years, the large martensitic stainless steel castings and advanced manufacturing technologies will see a huge demand in clean energy industry such as nuclear power, hydraulic power at home and abroad. Therefore, the new high yield o tensile strength (R p0.2/R m ) ratio and high obdurability martensitic stainless steel materials, the fast and flexible manufacturing technologies of large size castings, and new environment friendly sustainable process will face new challenges and opportunities.

Structure change of 430 stainless steel in the heating process

The microstructure analysis was employed for the ferrific stainless steel （SUS430） with the carbon content from 0.029wt% to 0.100wt% under the simulated heating process condition. The higher carbon sample （430H） contains the duplex phase microstructure at the temperature of 1150℃; on the other hand, the lower carbon content sample （430L） does not touch two phase area even at the temperature of 1450℃ and has the single phase ferritic microstructure. The carbon content need be well controlled for the 430 ferritic stainless steel since it can significantly affect the heating process curve, and the heating process may not be done in the two phase area due to the uncontrolled carbon content. With the low carbon content and the proper soaking time, the grain size is not sensitive to the heating process temperature and the soaking time. In the present heat treatment experiments, the soaking time is about 10 min, and the processing parameters can be chosen according to the requirement of the gross energy, the efficiency and the continual forming. 2008 University of Science and Technology Beijing. All rights reserved.

Effect of Mn on the microstructure and property of 13Cr stainless steel

Mn is a weak element for austenite formation and its effect on martensitic stainless steel is seldom researched. The microstructure and property of 13Cr martensitic stainless steel with varied Mn content and low carbon content were studied. The research demonstrates that Mn enlarges the austenitic zone at a high temperature and increases the strength and hardness of martensitic stainless steel. Following the addition of Mn,the corrosion resistance property of low carbon 13Cr stainless steel only decreases slightly. The strength and hardness of low carbon 13Cr stainless steel containing Mn is similar to that of high carbon 13Cr stainless steel.

Microstructure of stainless steel weld in double-sided arc welding

Double-sided arc welding with a single power source can effectively increase the weld penetration, diminish distortion, improve welding speed and save energy. Compared to conventional arc welding processes, double-sided arc welding can generate a penetrating electromaguetic field to help to form fine dendritic microstrueture in the weld due to the symmetry of heating. Type 1Cr1SNi9Ti aastenitic stainless steel was bead-on-plate welded with double-sided arc welding and conventional plasma arc welding processes, respectively, and microstructure in the weld, heat-affected zone and base metal were examined. After analyzing the black carbon-enriched band in the weld during plasma arc welding with electron probe microanalyzer （ EPMA ） and X-ray diffraction （XRD） technology, it was found that the black band was shaped from the aggregation of ferrite in the fasion boundary. Hardness measurement showed that this black band does not apparently affect the microhardncss distribution in the weld.

Cross wedge rolling deformation law and bonding mechanism of 304 stainless steel/Q235 carbon steel bimetallic shaft

304 stainless steel(SS)/Q235 carbon steel(CS)bimetallic composite shafts were prepared by the cross wedge rolling(CWR).The bonding interface welding mechanism was investigated through CWR rolling experiments and finite element simulation,as well as element diffusion,microstructure analysis,and mechanical property tests.According to simulation studies,the bonding interface is primarily subjected to three-directional compressive stresses at the tool-workpiece contact zone.As compression ratio increases from 0.25 to 0.35,the interface of the stress penetration area increases,while the diameter and wall thickness of CS/SS bimetallic shaft decrease,and hence,thickness-to-diameter ratio remains unchanged,which is conducive to the coordinated deformation of inner and outer metals and the interface of welded joints.The microstructure analysis of the interface shows that there are no obvious defects and cracks in the attachment,and that the microstructure on CS side is dominated by ferrite and martensite phases.Caused by the decarburization effect,Q235 steel microstructure features coarse ferrite,accompanied by a carburized layer with a thickness of about 20μm on SS side near the interface where grains are refined.As radial compression ratio increases,the diffusion distance of Cr,Ni,and other elements increases,the average thickness of the decarburized layer decreases,the interfacial bonding strength increases from 450 to 490 MPa,and metallurgical bonding at the interface is thus improved.The study demonstrates that it is feasible to use 304 SS and Q235 CS for cross wedge rolling composite shafts.

Effect of residual stress on the vibration failure of dissimilar steels joint

Elasto-plastic finite element method is used for the welding residual stress calculation in butt welded joint of carbon steel and stainless steel, fluctuating pressure on the ship hull induced by a propeller is calculated from the actual measurement data. As the result of the superposition of vibration load and welding residual stress, the stress amplitude is reduced slightly in high stress area near the welding line, while the value of stress reduction becomes larger when the welding current increases. On the contrary, the stress amplitude is increased clearly far from the welding line. The welding residual stress obviously reduced the fatigue life of ship structure with the vibration load. The fatigue lives of ship structures under vibration are - 1.75 × 105 （ 110 000 ton product carrier） and - 2.43 × 105 （52 000 ton all-purpose cargo ship） without welding residual stress, while the residual stress exists, the fatigue life is down to - 3 × 104.

Microstructure and Mechanical Properties of a Dissimilar Friction Stir Weld between Austenitic Stainless Steel and Low Carbon Steel

Dissimilar fusion welding of austenitic stainless steels to carbon steels has some metallurgical and technical problems. It was suggested that the solid-state nature of friction stir welding （FSW） can overcome these problems and produce a sound weld with reliable mechanical properties. In this study, plates of 304 stainless steel and st37 steel were welded together by FSW at tool rotational speed of 600 r/rain and welding speed of 50 ram/rain. In the stir zone （SZ） of 304 stainless steel, the results showed a refined grain structure with some features of metadynamic recrystallization. In the SZ of st37 steel, the hot deformation of material in the austenite region produced small austenite grains. These grains transformed to fine ferrite and pearlite by cooling the material after FSW. The production of fine grains increased the hardness and tensile strength in the SZ of both sides with respect to their base metals （BMs）.

Nanomechanical and Electrochemical Properties of Diamond-Like Carbon (DLC) Films Deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) Technique

Diamond-like carbon （DLC） films was deposited successfully on stainless steel sub- strates with Si/SiC intermediate layers by combining plasma enhanced unbalanced magnetron sputtering physical vapor deposition （PEUMS-PVD） and microwave electron cyclotron resonance plasma enhanced chemical vapor deposition （MW-ECR PECVD） techniques. The effect of sil- icon dopant on the structure, morphology, nanomechanical properties and electrochemical be- havior of DLC films were investigated by Raman spectroscopy, nano-indentation, atomic force microscopy （AFM） and potentiodynamic method and electrochemical impedance spectroscopy （EIS）. It showed that the incorporated silicon atoms substituted sp2-bonded carbon atoms in the ring structures, promoting the formation of sp3-bonds. The structural transition from C-C to C-Si bonds resulted in the relaxation of the residual stress, leading to the decrease in films hardness. The DLC films with Si/SiC intermediate layers led to significant improvement in the corrosion resistance of the stainless steel substrate due to effective isolation and good chemical inertness of the DLC films.

Stainless steel cloth modified by carbon nanoparticles of Chinese ink as scalable and high-performance anode in microbial fuel cell

Microbial fuel cells(MFCs) have various potential applications.However,anode is a main bottleneck that limits electricity production performance of MFCs.Herein,we developed a novel anode based on a stainless steel cloth(SC) modified with carbon nanoparticles of Chinese ink(Cl) using polypyrrole(PPy)as a building block(PPy/Cl/SC).After modification,PPy/Cl/SC showed a 30% shorten in start-up time(36.4 ± 3.3 h vs.52.3± 1.8 h),33% increase in the maximum current(12.4 ± 1.4 mA vs.9.3± 0.95 mA),and2.3 times higher in the maximum power density of MFC(61.9 mW/m^(2) vs.27.3 mW/m^(2)),compared to Ppy/SC.Experimental results revealed that carbon nanoparticles were able to cover SC uniformly,owing to excellent dispersibility of carbon nanoparticles in Cl.The attachment of carbon nanoparticles formed a fluffy layer on SC increased the electrochemically-active surface area by 1.9 times to 44.5 cm^(2).This enhanced electron transfer between the electrode and bacteria.Further,embedding carbon nanoparticles into the PPy layer significantly improved biocompatibility as well as changed functional group contents,which were bene ficial to bacteria adhesion on electrodes.Taking adva ntage of high mechanical strength and good conductivity,a large-size PPy/Cl/SC was successfully prepared(50×60 cm^(2))demonstrating a promising potential in practical applications.This simple fabrication strategy offers a new idea of developing low cost and scalable electrode materials for high-performance energy harvesting in MFCs.

Surface modification of 316L stainless steeldiamond-like carbon films

The diamond-like carbon(DLC)film on 316L stainless steel substrate was preparedpulsed plasma-enhanced chemical vapor deposition,and the performance of the films was optimizedregulating the pulse voltage.Microstructure and properties of DLC film on 316L stainless steel were characterizedatomic force microscopy,field-emission scanning electron microscopy,Raman spectra,nano-indenter and electrochemical workstations.The results showed that DLC films with smooth and dense morphology have a low friction coefficient and high nano-indentation hardness,and the surface hardness of 316L stainless steel substrate was enhancedmore than 3 times.The mechanical properties of DLC films and their bond with 316L stainless steel could be further optimizedincreasing pulse voltage.DLC films on 316L stainless steel substrate increased the self-corrosion potential0.173 V and decreased self-corrosion current99%,which significantly improved the anti-corrosive properties of 316L substrate.

Measurement of contact angle between stainless steel surface and carbon dioxide by pendant drop method

To measure contact angle between CO2 and solid surface, in this study a visual high-pressure vessel has been developed, with a corresponding well-controlled constant temperature system. Pendant drop method is applied to the investigation of the contact angles of CO2 on a stainless steel surface in its own vapor. The image of the pendant drop is recorded by a camera, and a B-Snake method is used to analyze the contour and the contact angle of the droplet. The experimental results have provided a set of well tested data, which show that CO2 has good infiltration into stainless steel surface and the de- veloped method can be used as a standard testing one for measuring the contact angle between high-pressure liquid and solid surface.

“双碳”战略背景下不锈钢复合钢板结构减碳前景分析

为探究不锈钢复合钢板结构的减碳前景,本文分析了“双碳”战略背景下钢结构行业的发展趋势,包括智能建造快速发展、新兴产业提供广阔市场以及高性能钢材和高性能结构发展更为迅猛,指出不锈钢复合钢板结构可兼顾高性能、经济性以及减碳要求。基于全寿命周期评价理论,采用排放因子法,提出了不锈钢复合钢板结构的碳排放计算方法。结果表明:不锈钢复合钢板结构的全寿命周期碳排放量比钢结构少36%,比不锈钢结构少10%。用不锈钢复合钢板结构替代普通钢结构,可以有效减少碳排放;替代不锈钢结构可以在减碳的同时具有良好的经济性。

温度和应变幅对亚稳奥氏体不锈钢S321低周疲劳行为的影响

在室温和650℃的环境下对S321、S321H不锈钢进行了0.5%、0.7%、0.9%应变幅下的低周疲劳试验,并在室温下对S321和S321H开展了多个寿命点的疲劳加载历史试验,结合X射线衍射定量分析测算形变诱发马氏体的含量。结果表明:形变诱发马氏体的生成会导致奥氏体钢持续循环硬化,室温下合金在初次硬化后继续二次硬化,而在650℃下没有形变诱发马氏体生成,合金在初次硬化后进入循环稳定阶段。循环过程中,碳含量越低,形变诱发马氏体含量越多,合金的循环硬化程度更高。两种温度下,两种材料的疲劳寿命在低应变幅下都相差不大,应变幅越大,两种材料的疲劳寿命相差越大,因此,可以考虑服役条件为低应变幅时使用S321不锈钢代替S321H不锈钢。

内置碳钢不锈钢管海洋混凝土柱轴压试验及承载力计算

为研究不锈钢管海洋混凝土柱及内配碳钢后的轴压力学性能,以型钢类型、螺旋筋间距、纵筋直径为变化参数,完成了10个试件的轴心受压静力加载试验。观察了试件的受力破坏全过程及形态,获取了轴向荷载-位移曲线及各钢材应变曲线,基于试验实测数据,就各变化参数对试件的轴压承载力、延性、耗能能力和损伤发展的影响规律进行了分析。结果表明:不同试件的破坏形态相似,均表现为不锈钢管局部屈曲压皱,混凝土斜向剪切破坏;内置碳钢可以提高试件的极限承载力、轴压延性和耗能能力,抑制试件的损伤发展;在增加相同用钢量的条件下,增加圆钢管含钢量对试件轴压性能提升幅度最大;基于“复合约束叠加法”推导计算公式所得承载力计算值与试验值吻合良好。