Study of the interfacial phenomena during friction surfacing of mild steel with tool steel and inconel

Friction surfacing was carried out with tool steel (AISI 01) and inconel 600 consumables on mild steel 1020 substrate in an argon atmosphere. Inconel bonded strongly with the substrate and there was evidence of interfacial compound formation between the substrate and coating. For tool steel coatings, a sharp boundary between the substrate and coating was observed by scanning electron microscopy. X-ray fluoroscopic imaging also revealed this boundary. Mechanical interlocking between the coating and the substrate appears to be insignificant so adhesion between the coatings and the substrate may be caused by solid-phase bonding. For friction surfacing of both tool steel and inconel, a nominal contact pressure as high as 21.8 MPa was required to obtain an adherent coating of uniform quality. © 1998 Chapman & Hall     

激光熔覆制备Fe3Al金属间化合物覆层的组织结构

为了研究激光熔覆工艺条件下Fe3Al金属间化合物合金层的组织结构特点,以纯Fe3Al粉 1%Y2O3为原料在钢基体表面激光熔覆Fe3Al金属间化合物,利用扫描电镜、能谱仪、X射线衍射试验方法等对熔覆合金层、合金层与钢基体的结合界面等进行了显微组织与相结构的分析.试验获得了致密、无肉眼可见气孔、夹杂的合金层,合金层与基体间完全冶金结合,但存在裂纹现象;熔覆合金层主要由单相Fe3Al构成,覆层组织为粗大等轴状晶团,等轴状晶团由大量极细小的条状Fe3Al晶粒构成,一些相邻的条状晶粒之间具有基本一致的晶体学取向.     

Characterization and properties of CuZrAlTiNi high entropy alloy coating obtained by mechanical alloying and vacuum hot pressing sintering

CuZrAlTiNi High entropy alloy (HEA) coating was synthesized on T10 substrate using mechanical alloying (MA) and vacuum hot pressing sintering (VHPS) technique. The MA results show that the final product of as-milled powders is amorphous phase. The obtained coating sintered at 950 °C is compact and about 0.9 mm in thickness. It is composed of a couple of face-centered cubic (FCC), one body-centered cubic (BCC) solid solutions and AlNi₂Zr phase. The interface strength between coating and substrate is 355.5 MPa measured by three point bending test. Compared with T10 substrate, the corrosion resistance of CuZrAlTiNi HEA coating is enhanced greatly in the seawater solution, which is indicated by the higher corrosion potential, wider passivation region, and secondary passivation. The average microhardness of the coating reaches 943 HV_0.2, and is about 3.5 times higher than the substrate, which is mainly ascribed to the uniformly dispersed nano-size precipitates, phase boundary strengthening and solid solution strengthening. Moreover, the wear resistance of the coating is slightly improved in comparison with the substrate.     

Special aspects of structure formation of a multicomponent layer in vacuum-arc plasma

A phase boundary is an energy barrier to diffusing atoms. To decrease the diffusion rate, densely packed multicomponent structures were used. The correlation between the methods of obtaining and properties of multicomponent coating formed in a single fabrication cycle upon step-by-step synthesis of carbide of a substrate material and sputter deposition of layers of zirconium and zirconium carbide was investigated.     

一种监控非规整膜系的新方法

由透过率和波长的函数关系可知,膜系中每一层都可能存在若干波长的光信号会出现极值偏转。利用这些波长作为每层膜的监控波长,满足光电极值法的监控条件,由此提出了一种监控非规整膜系的新方法。这些波长可以通过波长搜索的方法而得出。从监控模拟和随机误差曲线可知,该方法继承了光电极值法简单易行以及自动补偿等优点,其反射率在 0.1%范围内变化,与理论曲线基本吻合。     

Processes in interfacial zones during chemical vapour deposition: Aspects of kinetics, mechanisms, adhesion and substrate atom transport

An overview of the various sequential steps in a chemical vapour deposition (CVD) process is presented. The overview contains four different parts: basic concepts, the gas phase, reaction mechanisms, and the consequences and use of reactions between the substrate and the vapour. The basic concepts treated are reactor types, reaction zones, rate-limiting steps and control of CVD processes. The gas phase part includes gas flow patterns in CVD reactors, boundary layers and transport processes across them, and calculations of the deposition rates. Reaction mechanisms in CVD are illustrated for silicon CVD from chlorosilanes and for in situ phosphorus doping during silicon growth. Finally aspects of adhesion, introduction of substrate material into the coating and selective growth are discussed in terms of interfacial reactions between the substrate and the vapour.     

钛合金表面电泳沉积法制备YSZ/HAp纳米复合涂层

采用电泳沉积法在钛合金基体上制备了YSZ/HAp纳米复合涂层,用场发射扫描电镜、X射线衍射和能量散射谱对复合涂层HAp外层的表面形貌和晶相、复合涂层的断面形貌及元素组成分布进行分析研究,通过粘结-拉伸实验测定了涂层与基体的结合强度.结果表明YSZ/HAp纳米复合涂层与钛合金基体的结合强度明显高于HAp单一涂层与钛合金基体的结合强度,说明YSZ/HAp的复合缓和了HAp涂层与钛合金基体之间的热膨胀系数失配现象,改善了涂层与基体之间的结合.     

钼网表面MoSi2涂层的制备及其1500℃高温氧化性能

钼网被广泛用作高温催化剂载体,但关于其高温防护涂层的制备及失效机制却鲜有报道.用包埋渗硅方法在钼网表面制备了MoSi2高温抗氧化涂层,并在静态大气环境中开展了1500℃恒温氧化试验.利用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱分析(EDS)等对氧化前后涂层的微观形貌和组织结构进行了表征.结果表明:1500℃氧化2h,MoSi2涂层中的Si元素会发生选择性氧化,在涂层表面形成一层连续的、具有“自愈合”功能的熔融态SiO2保护膜,阻挡氧向基体一侧的扩散,展现出了良好的高温抗氧化性能;高温条件下,涂层中的Si元素会和钼基体发生界面扩散反应生成抗氧化性能差的Mo5Si3,同时MoSi2不断地和氧发生反应生成Mo5Si3和SiO2,当涂层中的MoSi2完全转化为Mo5Si3,涂层将快速氧化失效.     

氧化锆基羟基磷灰石梯度涂层材料的研究

本文采用涂覆－烧结法制备了一种以氧化锆为基体的生物玻璃－羟基磷灰石梯度涂层材料，并对其热学、力学性能进行了测试。实验发现，在生物玻璃－羟基磷灰石梯度设计时，羟基磷灰石含量对复合体材料的热膨胀性能有着较大的影响。这种影响的原因是，随着羟基磷在石含量的变化，复合体材料的结构发生改变，从玻璃相为主晶相向羟基磷灰石为主晶相转变。文中对梯度涂层各层中的热尖力进行了计算，其结果与涂层－基体的结合强度相吻合。     

氧化锆基羟基磷灰石梯度涂层材料的研究

本文采用涂覆-烧结法制备了一种以氧化锆为基体的生物玻璃-羟基磷灰石梯度涂层材料，并对其热学、力学性能进行了测试实验发现，在生物玻璃-羟基磷灰石梯度设计时，羟基磷灰石含量对复合体材料的热膨胀性能有着较大的影响．这种影响的原因是，随着羟基磷灰石含量的变化，复合体材料的结构发生改变，从玻璃相为主晶相向羟基磷灰石为主晶相转变．文中对梯度涂层各层中的热应力进行了计算，其结果与涂层-基体的结合强度相吻合.     

A study on hybrid bioceramic coatings of HA/poly(vinyl acetate) co-deposited electrochemically on Ti–6Al–4V alloy surface

A novel electrochemical co-deposition approach was developed to prepare hybrid bioceramic coating of hydroxyapatite (HA)/poly(vinyl acetate) on the surface of Ti–6Al–4V alloy. The aim is to improve the adhesion between the HA coating and the metal substrate. Surface characterization showed that the composition of inorganic phase in the composite bioceramic coatings was mainly HA and the content of organic phase was more than 4% (W/W). Significant surface morphology changes were observed. The shear-testing experiments indicated that the bonding strength of the hybrid coating to metal substrate was increased by as much as 3 MPa.     

钛板表面激光熔覆锆基合金涂层的组织结构

利用激光熔覆技术在Ti板上制备了非晶复合涂层,利用X射线衍射仪、能谱仪、扫描电镜和透射电子显微镜对熔覆层和结合区的组织结构进行了表征。研究发现,熔覆层组织主要由非晶、Zr的金属间化合物、氧化物及局部纳米晶组成。基体与熔覆层结合区由Ti的柱状晶和α(Ti/Zr)固溶体所构成,保证了基体与熔覆层之间有良好的冶金结合。     

Ion-plated titanium carbide coatings

A new development in the field of coatings is the reactive ion-plating process. In this process, metal evaporated from a source reacts with an atmosphere of mixed gases. The reaction can take place in the gas phase before the material deposits, or it can take place on the substrate. The stoichiometry of the reaction can be controlled by adjusting at least one of several process parameters. This technique allows the formation of carbides, nitrides, oxides and other materials and provides a method of controlling the stoichiometry of the deposited material. The ability of the process to provide graded stoichiometry through a coating layer has made possible the application of adherent coatings to difficult-to-coat substrates. This prevents, for instance, a sharp boundary zone between materials which have greatly differing thermal coefficients of expansion. The dependence of the coating composition upon the deposition parameters of gas pressure, substrate voltage and evaporation rates from the source is discussed. The application of the technique in the coating of titanium and mild-steel substrates with titanium carbide is discussed. Photomicrographs and hardness data for the deposited films are presented.     

304不锈钢激光原位合成自润滑涂层的宽温域摩擦学性能

由于304不锈钢在中、高温下摩擦学性能较差,制约了其在重要摩擦运动副零部件上的应用。为改善304不锈钢的摩擦学性能,以Ni60粉末为增韧相,WS2为合成润滑相的前驱化合物,TiC为高硬度耐磨相,采用高能激光束在其表面原位合成自润滑耐磨复合涂层。利用X射线衍射仪、扫描电子显微镜、显微硬度计、摩擦磨损试验机和探针式材料表面磨痕测量仪表征涂层和基体的物相、微观结构、显微硬度与表面形貌,并系统研究涂层和基体在20,300,600,800℃下的摩擦学性能及其磨损机理。结果表明:涂层主要由Cr0.19Fe0.7Ni0.11,Ti2SC,Fe2C,Cr7C3,CrS和WS2组成;涂层的平均显微硬度(302.0HV0.5)略高于基体(257.2HV0.5),但涂层上部区域的硬度(425.4HV0.5)约为基体的1.65倍;涂层在所有等温摩擦学实验中摩擦因数和磨损率均低于基体,300℃时涂层润滑效果最好,摩擦因数为0.3031,600℃时涂层耐磨效果最好,磨损率为9.699×10^-5 mm^3·N^-1·m^-1。     

钛涂覆多孔羟基磷灰石涂层的制备及其生物活性

在纯钛基体表面通过电泳沉积的方法制得壳聚糖/羟基磷灰石(CS/HA)复合涂层, 然后将复合涂层烧结形成多孔HA涂层。采用SEM对多孔HA涂层的形貌进行观察, XRD分析涂层的物相组成, 粘结拉伸实验测定涂层与基体的结合强度, 1.5倍人体模拟体液(1.5SBF)浸泡测定涂层的生物活性。结果表明: 当悬浮液中CS与HA质量比为1∶1时, 制得的CS/HA复合涂层经过700℃烧结处理, 涂层中CS热分解致孔形成多孔HA涂层, 孔径在10~25 μm, 涂层与基体的结合强度可达19.5 MPa; 在1.5SBF中浸泡5天后, 多孔HA涂层表面完全碳磷灰石化, 呈现较好的生物活性。      

电弧喷涂Al,45CT及其复合涂层的抗高温氧化性能与机理

为获得抗氧化性能优良的涂层,采用电弧喷涂方法制备了Al,45CT及其复合涂层,探讨了3种涂层过渡层的形貌、物相及其相应的作用,分析了3种涂层的组织结构、抗氧化性能与机理。结果表明:Al涂层和复合涂层高温氧化后表面氧化膜有剥落现象,涂层中的抗氧化元素Cr含量很低;45CT涂层中的抗氧化元素Cr含量仍然很高,涂层的自我修复能力很强,表面生成的Cr2O3氧化膜具有优异的抗氧化性能;在涂层与基体结合处有一层过渡层,不仅增强了涂层与基体的结合力,还能进一步阻止氧化性气体向基体入侵,起到二次保护作用。     

超音速冷喷涂Cu-Al_2O_3复合涂层特性

采用冷喷涂技术在铝基板上制备了Cu-Al2O3复合涂层,以复合涂层为催化荆进行了甲醇水蒸气重整制氢实验,并利用扫描电镜、能谱分析仪和X射线衍射仪对实验前后的涂层进行了表征.结果表明,涂层之间和涂层与基板问的结合主要为机械咬合,孔隙率较高,与喷涂颗粒相比,涂层没有相的变化;喷涂后Al2O3颗粒发生了破碎,而Cu颗粒变形不充分,Cu颗粒特性导致涂层中铜含量比粉末中的低;甲醇水蒸气重整制氢实验表明,Cu-Al2O3复合涂层由于含氧高而具有比纯铜涂层更好的稳定性.     

Microstructural characterization of Co-based coating deposited by low power pulse laser cladding

A detailed microstructural study of Stellite 6 coating deposited on a low carbon ferritic steel substrate using preplaced powder method and low power Nd:YAG pulse laser is performed. The grain structure and solidification texture of the coating are investigated by orientation imaging microscopy (OIM) and scanning electron microscopy. In addition, the effect of consecutive pulses on the microstructure of the coating is examined. The orientation relationship (OR) at coating/substrate interface and the solid state phase transformation in heat-affected zone are studied as well as the Vickers microhardness profile measurement in order to support the microstructural observations. An important conclusion is reached that the shape of solidification front during pulsed laser cladding is similar to the shape of solidification front during continuous cladding with a doubled laser beam scanning speed. Further, OIM reveals the Greninger–Troiano OR between the face centered cubic coating and bcc substrate grains. It is concluded that at the moment of solidification epitaxial growth of the grains in the coating occur on the austenitic grains of the substrate and that an austenite–ferrite transformation occurs in the heat-affected zone upon subsequent cooling.     

Microstructural control of boundary region between CVD diamond film and cemented carbide substrate

Effects of the composition, texture and pretreatment of cemented carbide substrates on the microstructure of the boundary region between CVD diamond film and the substrate were investigated using a microwave plasma CVD in the CO-H₂ system. Optimum CVD conditions for a uniform coating on to the edge part of cutting insert were: microwave power, 550 W; total pressure, 30 Torr; total flow rate, 200 ml/min; CO concentration, 5–20 vol%; treatment time, 3–5 h. An adherent and tough diamond coating was prepared by initial coating at lower CO concentrations and by subsequent coating at higher CO concentrations. A cemented carbide substrate in the binary WC-Co system which comprised fine-grained tungsten carbide and low content of cobalt was suited for preparation of adherent diamond coating. De-cobaltization pretreatment of the substrate surface in acid solution followed by an ultrasonic microflawing treatment enhanced the nucleation density and adherence of diamond film to the substrate. The rotation of substrate was found to be effective for increasing the uniformity and decreasing the grain size of diamond film.     

Boundary Element Method (BEM) Analysis for Galvanic Corrosion of Hot Dip Galvanized Steel Immersed in Seawater

A numerical analysis of galvanic corrosion of hot-dip galvanized steel immersed in seawater was presented.The analysis was based on the boundary element methods (BEMs) coupled with Newton-Raphson iterative technique to treat the nonlinear boundary conditions, which were determined by the experimental polarization curves. Results showed that galvanic current density concentrates on the boundary of steel substrate and zinc coating, and the sacrificial protection of zinc coating to steel substrate results in overprotection of steel cathode. Not only oxygen reduction but also hydrogen reduction could occur as cathode reactions, which probably led up to the adsorption and absorption of hydrogen atoms. Flat galvanized steel tensile sample shows a brittle behavior similar to hydrogen embrittlement according to the SSRT (show strain rate test) in seawater.