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.

Plasma Surface Cu Alloyed Layer as a Lubricant on Stainless Steel Sheet:Wear Characteristics and On-job Performance in Incremental Forming

To solve the problems of poor forming and easy adhesion of the stainless steel,Cu alloyed layer on the stainless steels was prepared by the double glow plasma surface alloying technique.The experimentalresults indicated that the supersaturated copper dispersedly precipitated in grain interior and crystalboundaries and formed the vermicular structure.The tribologicaltests indicated that the friction coefficient of the Cu alloyed layer was lower than that of the stainless steels.The wear rate of stainless steelin the presence of Cu alloyed layer was approximately 2-fold lower than that in the absence of the alloyed layer.The results of the incrementalforming indicated that the ploughing phenomenon was not observed on the stainless steelin the presence of Cu alloyed layer during the incrementalforming,while the stainless steelpresented the deep ploughing.Therefore,Cu alloyed layer on stainless steelexhibited excellent self-lubrication and forming properties.

Analysis on interfacial layer of aluminum alloy and non-coated stainless steel joint made by TIG welding-brazing

Dissimilar metals TIG welding-brazing of aluminum alloy and non-coated stainless steel was investigated. The resultant joint was characterized in order to identify the phases and the brittle intermetallic compounds （IMCs） in the interracial layer by optical metalloscope （OM）, scanning electron microscopy （SEM） and energy dispersive spectrometer （ EDS） , and the cracked joint was analyzed in order to understand the cracking mechanism of the joint. The results show that the microfusion of the stainless steel can improve the wetting and spreading of liquid aluminum base filler metal on the steel suuface and the melted steel accelerates the formation of mass of brittle IMCs in the interracial layer, which causes the joint cracking badly. The whole interfacial layer is 5 -7 μm thick and comprises approximately 5μm-thickness reaction layer in aluminum side and about 2 μm-thickness diffusion layer in steel side. The stable Al-rich IMCs are formed in the interfacial layer and the phases transfer from （ Al ＋ FeAl3 ） in aluminum side to （ FeAl3 ＋ Fe2Al5 ） and （ α-Fe ＋ FeAl） in steel side.

Diffusion bonding of copper alloy to stainless steel with Ni and Cu interlayer

CuAlBe alloy is an attractive shape memory alloy with many important usages in industrial field, in order to spread its range of application it is desirable to be able to join CuAlBe soundly with other metallic materials, for example stainless steel; however the weldability between CuAlBe alloy and stainless steel has never been studied, therefore an experimental investigation of different transition metals was carried out in the diffusion bonding joints of Cu alloys (CuAlBe) to stainless steel (1Cr18Ni9Ti). The microstructure and phase composition of the joint were analyzed by SEM, EPMA and X ray diffraction. The following conclusions have been drawn: 1) The joint strength with Ni interlayer is higher than that with Cu interlayer when the welding parameters are the same; 2) When Ni interlayer is thinner, Al will interact with Ni and Fe, and the intermetallic compounds such as Fe 3Al are formed in the interface, which decreases the strength of the joints; 3) When the bonding temperature is higher, because the diffusion of Cu in Ni is faster than Ni in Cu, a Kirkendall effect occurs, which also decreases the strength of the joints.

XTEM STUDY ON ION PLATED STAINLESS STEEL MULTI-LAYER FILMS

In this paper, the cross sectional microstructure and crystal structure of ion plated multi layer films of stainless steel (1Cr18Ni9Ti ) were studied by cross sectional transmission electron microscopy (XTEM). The results show that ion plated stainless steel multi layer films are fine grained double phase steel films of austenites and ferrites.Cross section film growing microstructures can be divided into three zones: fine equiaxed crystals, fine columnar crystals and coarse columnar crystals. Interfaces in multi layer films can promote fine grained growing and interrupt columnar grained growing,and improve properties of film materials.

Droplet transfer behavior of the stainless steel coated electrode with double-layer coating

In this paper, the droplet transfer behavior of the stainless steel coated electrode with double layer coating is researched by means of those experimental methods, such as high speed camera, collecting droplet in water, surfacing on the steel plate et al. The results show that the droplet transfer indexes of coated electrode are mainly controlled by the size of droplet, which affects the transfer behavior of droplet. The distribution characteristic of the droplet size of the electrode affects the numerical relationship among droplet transfer indexes. The metallurgical process of the coated electrode with double layer coating is carried out continuously in different zones. The main reason for the coated electrode with double layer coating gaining excellent usability quality is that the droplets realize the 'quasi flux wall guided transfer pattern'.

Formation of microstructural features in hot-dip aluminized AISI 321 stainless steel

Hot-dip aluminizing（HDA） is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions： an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al_7Cr and Al_3Fe dispersed in an Al matrix. Twinning was observed in both the Al_7Cr and the Al_3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe_2Al_5, Al_7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed.

High-temperature oxidation behavior of heat resistant stainless steel 1.4828

The kinetic curves of the high-temperature oxidation of austenitic heat resistant stainless steel 1. 4828 at 1 050 ℃ were measured using a weighing method. It is shown that the oxidation curves at 1 050 ℃ followed the parabolic line law, and after 250 h of oxidation, the mass gain was about 80 g/m2. The surface morphology and structure of the oxide layers were studied by scanning electron microscopy and X-ray diffraction. A complicated oxide layer obtained at 1 050 ℃ was mainly composed, from inner to outer, of （FeSi） 3 04, Cr2 03, Fe2 03, and spinel oxides FeCr204 and NiMn204.

Preparation and Characterization of Plasma Cu Surface Modified Stainless Steel

Cu modified layer was prepared on the surface of AISI304 stainless steel by plasma surface alloying technique. The effects of processing parameters on the thickness, surface topography, microstructure and chemical composition of Cu modified layer were characterized using glow discharge optical emission spectroscopy （GDOES）, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The experimental results show that the surface modified layer is a duplex layer （deposited ＋ diffused layer） with thickness of about 26 ktm under the optimum process parameters. The modified layer is mainly composed of a mixture of Cu and expanded austenite phase. The ball-on-disk results show that the modified layer possesses low friction coefficients （0.25） and excellent wear resistance （wear volume 0.005 x 109 um3）. The Cu modified layer is very effective in killing the bacteria S. aureus. Meanwhile, no viable S. aureus is found after 3 h （100% killed） by contact with the Cu alloyed surface.

EFFECT OF COPPER IMPLANTATION ON ANTIBACTERIAL ACTIVITY OF AUSTENITIC STAINLESS STEEL

Antibacterial activity has been studied by copper ion implantation into 0Cr18Ni9 stainless steel. Ions extracted from a metal vapor vacuum arc (MEVVA) are sourced with 60-100keV energy and a dose range (0.2-2.0)×1017 ions cm-2. Saturation doses, surface concentration were calculated and the relationships between energy, dose and antibacterial activity were analyzed. Novel phases such as Fe4Cu3 and Cu0.81Ni0.19 were found after copper implantation by X-ray diffraction. The novel phases, effects on antibacterial activity have been investigated. The results show that saturation dose varies with the ions' energy. Antibacterial activity has close relation with copper,s concentration in implanted layer and Cu-rich phase.

添加中间层的TC2钛合金/321不锈钢真空扩散焊研究

目的以Cu箔、Ni箔为中间层,使用真空扩散焊工艺实现TC2钛合金与321不锈钢的焊接。方法采用扫描电子显微镜、EDS能谱仪、X射线衍射仪、冲击韧性实验机、显微硬度计等仪器研究了焊接温度、典型中间层材料等工艺参数对TC2钛合金/321不锈钢焊接界面微观结构、界面元素扩散、接头力学性能的影响规律。结果在添加中间层的扩散焊接头中,是否会形成界面区和扩散区以及界面区和扩散区的宽度,受焊接温度的影响,也受中间层和母材成分及性能的影响。在以Ni为中间层的TC2钛合金与321不锈钢真空扩散焊接头中,扩散区会产生AlNi_(3)、NiTi等新物相,当以Cu为中间层时,扩散区中会产生Cu_(0.81)Ni_(0.19)等新物相。在实验条件下,使用铜箔作为中间层的TC2钛合金与321不锈钢真空扩散焊接头的力学性能优于使用镍箔作为中间层的真空扩散焊接头的力学性能。结论在实验条件下,添加中间层的TC2钛合金/321不锈钢真空扩散焊的最佳工艺参数如下:真空度为10^(-4)Pa,焊接温度为820℃,焊接压力为15MPa,焊接时间(即保温时间)为90min,保压时间为240min,以Cu作为中间层。

基于316L过渡层的431不锈钢激光熔覆层组织与性能研究

采用激光熔覆技术制备316L不锈钢涂层作为过渡层,在过渡层表面激光熔覆431马氏体不锈钢作为表面熔覆层.通过OM和SEM观察分析了熔覆层截面的微观组织特征,并借助XRD分析了熔覆层和过渡层的物相组成,利用显微硬度仪和电化学工作站测试熔覆层的硬度分布和耐腐蚀性.试验结果表明:加入过渡层后获得的熔覆层表面光滑平整,没有气孔裂纹等缺陷;表面熔覆层由马氏体、铁素体和少量残余奥氏体组成,过渡层由奥氏体组成;整个熔覆层的硬度从顶端向下呈现出梯度减小,表面熔覆层的硬度为538 HV,比基材提高了3倍,过渡层的平均硬度为300 HV;熔覆层的腐蚀电流为0.9569×10^(-6) A/cm^(2),腐蚀电位为-0.16644 V,熔覆层的耐腐蚀性优于基材.

引江济淮钢渡槽316L+Q345qD不锈钢复合板焊接接头过渡层厚度对焊接接头性能影响的研究

本文所涉及不锈钢复合板均采用桥梁钢板上复不锈钢板的形式,板间设置不同过渡层,复合板最大厚度24mm。为研究过渡层厚度对复合钢板性能的影响,对复合板的焊接接头进行试验分析,试验结果表明,采用不同厚度过渡层的复合板焊接接头,力学性能满足标准要求,并且选用较小的过渡层厚度可以降低成分稀释现象,保证焊接质量。

不锈钢双极板涂层-TiO_(2)薄膜的导电耐腐蚀行为研究

为了提高燃料电池金属双极板的导电耐腐蚀性,本文采用原子层沉积(ALD)工艺,在不锈钢316L上制备了TiO_(2)纳米薄膜,对比了不同加热温度以及基板加热与否时薄膜的导电耐腐蚀性能。结果表明,当加热250℃且基板不加热时,0.84 V恒电位腐蚀24 h,双极板涂层-TiO_(2)薄膜的电流密度最小,为1×10^(-10)A/cm^(2),且腐蚀前后接触电阻相对较小,导电和耐腐蚀性能均表现优异。通过XPS分析腐蚀前后薄膜表面的成分结构,发现二氧化钛保持了较稳定的结构,接触电阻增大主要源于表面C的氧化。

AISI 300系列奥氏体不锈钢渗氮层组织和性能研究

目的在AISI 300系列奥氏体不锈钢表面制备单一S相渗氮层,提高该系列不锈钢渗氮层的硬度、抗磨损性能,对比揭示渗氮前后不锈钢的磨损机制。方法采用低温辉光等离子渗氮技术(LTPNT)在AISI 300系列奥氏体不锈钢表面制备渗氮层。利用光学显微镜(OM)、扫描电子显微镜(SEM)、电子探针(EPMA)、X射线衍射仪(XRD)分析渗氮层的截面形貌、元素分布和物相组成;通过比磨损率和磨痕形貌分析渗氮层的摩擦学性能;利用电化学实验考察渗氮前后3种不锈钢的耐蚀性。结果AISI 300系列奥氏体不锈钢经380℃、12 h处理后,其表面获得了厚度为15μm左右、与基体致密结合、组织成分均匀的渗氮层;渗氮层的相结构主要为S相,无CrN相析出;经渗氮后,该系列不锈钢表面硬度均为1100HV左右,较基体硬度提高了5倍左右;不锈钢基体的磨损机理为黏着和磨粒磨损,经渗氮后转变为氧化磨损和微切削;渗氮层的比磨损率约为不锈钢基体的1/20,抗磨损的能力得到显著提升;在25℃环境温度下渗氮后,304L、316L和321的自腐蚀电位下降,腐蚀电流密度增加,腐蚀速率加快,耐腐蚀性能稍有降低。通过对比腐蚀形貌发现,渗氮层仍具有一定的耐蚀性能。结论通过LTPNT可以获得高硬度、组织均匀致密、结合强度高的渗氮层,渗氮层中S相的存在可以显著提高AISI300系列奥氏体不锈钢的表面硬度、抗磨损能力,降低其摩擦因数和比磨损率,对延长不锈钢的服役寿命有着积极的作用。

高功率选区激光熔化成形316L不锈钢层厚与性能的关系

采用高功率选区激光熔化技术和不同层厚(150、200、250μm)进行316L不锈钢粉末的单道成形、块体成形和拉伸试样成形试验,研究了单道形貌、块体致密度和截面组织、拉伸性能等。结果发现,平均熔宽随着层厚的增加而增加;相同层厚时,曝光时间越长,熔宽也越大。单熔道稳定成型随层厚的增加所需的曝光时间增大。三种层厚下均出现了液滴飞溅情况,液滴飞溅的程度随着层厚的增加而增加;相同层厚时,曝光时间越长,液滴飞溅的颗粒物越大。同等条件下,随层厚增大,成型效果逐渐变差。其中,150μm层厚时,致密度最大,达到99.9%,200μm层厚的力学性能最佳。250μm层厚时,晶粒尺寸较大,致密度较差,力学性能较差。粉层厚度不能无限增加,需在一个合理的参数范围内,以保证成形的效果。

STUDY ON FORMATION MECHANISM OF ADHERING LAYER FORMED ON TOOL FACE

The appearance of adhenng layer formed on tool face, its composition and distributionare analysed when Ca-S free-cutting stainless steel is machined. Cutting temperature field and itsrelation with formation of the layer is also studied. The result shows that, the layer can be formed under proper temperature condition, the stable cutting temperature field keeps the stable layer, itsthickness and composition distribution along rake face depend on the corresponding cutting tem-perature field. The theoretical model of the layer formation is set up.

钛合金管件与不锈钢内衬管真空扩散焊工艺研究

采用真空扩散焊工艺实现了TC4钛合金管件与15-5PH不锈钢内衬管的连接,研究了焊接温度、保温时间、中间层等对焊接界面结构、界面扩散及焊合率的影响规律。结果表明,在焊接温度为900℃,保温时间为4 h,Ni中间层厚20~30μm的条件下,可实现TC4管件与15-5PH内衬管的有效连接,焊合率最高。焊接接头界面产物组成,从钛合金侧到不锈钢侧依次为:TC4-(α+β)—NiTi_(2)—Ni_(x)Ti_(y)P_(z)—Ni_(3)Ti—FeNi_(3)—γ-(15-5PH)。焊接温度和中间层是影响连接质量最主要的因素,采用低于880℃的焊接温度或不采用中间层时,无法实现TC4管件与15-5PH内衬管的可靠扩散连接。保温时间为4 h时,焊接温度从890℃升高到910℃,焊合率和扩散层厚度先升高后略降低。焊接温度为900℃时,保温时间从2 h延长到4 h,焊合率和扩散层厚度均升高。

基于响应曲面法优化2205双相不锈钢层等离子弧熔覆工艺

采用等离子弧熔覆技术在Q345钢表面制备2205双相不锈钢层,采用响应曲面法研究了熔覆速度(3~7 mm·s^(-1))、熔覆电流(83~117 A)和送丝速度(43~77 mm·s^(-1))及其交互作用对熔覆层稀释率与宽高比的影响,得到优化的等离子弧熔覆工艺。结果表明:为获得稀释率低的熔覆层,需采用小熔覆电流和高送丝速度,为获得宽高比大的熔覆层,需采用大熔覆电流和低送丝速度,熔覆速度对稀释率和宽高比的影响均小;预测得到优化工艺参数为熔覆电流99 A、熔覆速度6 mm·s^(-1)、送丝速度50 mm·s^(-1),熔覆层的稀释率和宽高比分别为14.8%和4.36,与试验值的相对误差分别为2.9%和2.3%,说明采用响应曲面法建立的二次数学模型可靠。优化工艺下制备的熔覆层成型较好。

试样遮挡方式对316 L钢离子碳氮共渗渗层均匀性及防腐性能的影响

为了改善离子碳氮共渗(PNC)过程中的边缘效应,研究了316L钢在同一工艺条件下常规离子碳氮共渗(R-PNC)、试样有部分遮挡下碳氮共渗(PC-PNC)、试样在完全遮挡下碳氮共渗(CC-PNC)时,渗层的均匀性及耐蚀性。利用光学显微镜(OM)、原子力显微镜(AFM)、CHI660E型电化学工作站等对渗层结构及耐蚀性能进行了表征。结果表明:R-PNC时,渗层边缘效应明显,试样中心无渗层,耐蚀性较差;PC-PNC时,渗层的均匀性及耐蚀性得到改善,但试样中心仍有无渗层点;CC-PNC时,试样渗层厚度显著增加,边缘效应基本消失,耐腐蚀性比PNC及PC-PNC大幅提升。遮挡方式可改变渗镀过程中试样表面的电场分布、离子运动方向与离子能量等,从而改善渗镀中存在的边缘效应。遮挡板与渗镀面之间的间距为8~10 mm时,有良好的渗镀效果,最佳遮挡间距为8 mm,优化工艺已获得生产应用。