电镀锌层表面黑变膜的研究

用ＳＥＭ、ＥＤＸ、ＸＲＤ、ＸＰＳ等技术分析了电镀锌层表面黑变膜的组成和结构。结果表明,黑变膜是锌的腐蚀作用及杂质Ｐｂ去极化作用的共同产物。它由ＺｎＯ、Ｚｎ５（ＣＯ３）２（ＯＨ）６及微量ＰｂＯ组成,膜表层Ｚｎ是以ＺｎＯ形态存在,而膜内层则以非化学计量化合物ＺｎＯ１－ｘ形态存在。并发现黑变膜是一种锌受腐蚀所形成的表面膜上产生的光干涉现象。     

Investigations of plasma polymerized SiOx barrier films for polymer food packaging

Nano-scale SiO_x layers were deposited on polyethylene terephthalate (PET) foils by plasma enhanced chemical vapor deposition (PECVD) in an electron cyclotron resonance (ECR) plasma process in order to enhance their barrier properties towards water vapor. Oxygen (O₂) and hexamethyldisilazane (HMDSN) served as reactive gas and precursor, respectively. The effect of layer thickness and O₂:HMDSN (x:1) gas mixture ratio on the water vapor transmission rate was systematically investigated. Measurements by infrared spectroscopy and scanning electron microscopy for the characterization of the chemical composition and of the surface structure of the SiO_x layers, respectively, showed that both chemical composition and surface structure of the layers have a noticeable effect on their barrier properties. For low O₂ content in the O₂:HMDSN gas mixture ratio, organic layers were deposited. When increasing the O₂ content, the growing number of inorganic compounds in the SiO_x layers found by the infrared spectroscopy gave rise to a decrease in the water vapor transmission rate. A reduction of the water vapor permeation by more than a factor of 2 in comparison with the uncoated PET foil was achieved by the best performing SiO_x layer. Further increase of the O₂ content led to the onset of a columnar-like layer growth which showed to be causative for the water vapor permeation rising again.Finally, the barrier properties towards water vapor of 100 nm thick SiO_x films deposited from different O₂:HMDSN gas mixtures were contrasted with their corresponding barrier properties towards O₂. The minimum water vapor and O₂ permeation results were found for the SiO_x films plasma deposited from almost identical O₂:HMDSN gas mixture ratios in the range of 25 ≤ x ≤ 30.     

Bio-mimetic surface structuring of coating for tribological applications

A novel multilayered coating was developed for applications associated with friction reduction and wear resistance improvement. The nano-engineered coating integrates a soft lubricating layer, consisting of MoS₂-PTFE, onto hard load-supporting layers, with controlled surface morphology (roughness and patterning) of cBN-TiN. The coating was synthesized by sequential procedures including electrostatic spray deposition of cBN particles with different average particle sizes, chemical vapor deposition of TiN, deposition of nano- and micro-sized MoS₂ dispersed in PTFE, and curing. The effect of cBN particle size (with different combinations of particle size) and deposition parameters (specifically electrical voltage) on the cBN-TiN surface morphology were studied experimentally and optimized. SEM characterization of the as-synthesized cBN-TiN coating shows surface features similar to that of colocasia esculenta, with alternating nano- and micro-sized domes and “pockets”; the MoS₂-PTFE top layer has MoS₂ particles retained in the pockets by a basket structure formed during PTFE curing. Tribological and scratch tests were carried out for the as-prepared cBN-TiN and cBN-TiN/MoS₂-PTFE multilayered coatings. Sliding test results demonstrate significantly lower friction coefficient for the multilayered coating, showing that the unique integration of soft lubricating layer and biomimetically structured hard layer can effectively improve tribological performance. It is suggested that lubrication at the frictional contacts was realized by continuous release of the lubricants, MoS₂ and PTFE, from the pockets.     

稀土Y2O3对6063Al激光熔覆镍基熔覆层耐磨性的影响

利用激光熔覆技术,在6063铝合金表面制备了添加有不同含量Y₂O₃的Ni60合金熔覆层,并对熔覆层进行了耐磨性试验. 通过分析熔覆层组织、熔覆层表面磨痕形貌、磨损量及摩擦系数,研究Y₂O₃含量对铝合金表面激光熔覆Ni基涂层耐磨性能的影响. 结果表明,添加5%Y₂O₃的Ni60熔覆层组织呈现明显的网状分布的枝晶和细小的等轴晶,稀土Y₂O₃可以改善铝合金表面Ni60熔覆层的组织,促进晶粒细化和成分分布均匀;添加稀土Y₂O₃的Ni60基熔覆层较Ni60熔覆层的磨损面崩损程度减小了,摩擦稳定性得到提高;随着稀土含量提高,熔覆层的磨损量减小,但Y₂O₃含量高于5%时磨损量基本不会大幅变化;5%Y₂O₃+Ni60熔覆层具有良好的磨损形貌、较低的磨损量以及较稳定的摩擦系数,其熔覆层的耐磨性是Ni60熔覆层的6.1倍,是6063Al合金基体耐磨性的20.1倍.     

Investigations on composition and morphology of electrochemical conversion layer/titanium dioxide deposit on stainless steel

In this study, the formation and characterization of conversion coatings modified by a sol-gel TiO₂ deposit were investigated as a way to develop a new photocatalyst for water and air depollution. The conversion coating, characterised by strong interfacial adhesion, high roughness and high surface area facilitates the sol-gel deposition of titania and enhances its adhesion to the substrate. The conversion treatment is carried out in an acid solution. Observation by Scanning Electron Microscopy (SEM) reveals a rough surface with pores and cavities. According to SIMS measurements, the thickness of the initial conversion layer is evaluated at about 1.5 μm. On this pre-functionalised support, the titanium dioxide was deposited by the sol-gel method. The roughness measurements coupled with SIMS analysis allowed a precise evaluation of the surface state of the final layers. The coating consists of two layers: a TiO₂ outer layer and an inner layer containing iron chromium oxides. Characterization by X-ray diffraction (XRD) showed the existence of the TiO₂ anatase structure as the main compound.     

Fracture Toughness of Thick Boride Layers Estimated by the Cross-Sectioned Scratch Test

New results about the fracture toughness (K_c) of thick boride layers estimated by the cross-sectioned scratch test are presented in this study. The FeB-Fe₂B layers developed at the surface of borided AISI 1018 and AISI 1045 steels and the Fe₂B layer formed on the borided AISI 1045 steel exposed to a diffusion annealing process (DAP) were used for this purpose. The cross-sectioned scratch tests were performed with a Vickers diamond stylus drawn across the thick boride layer under a constant load to produce a half-cone-shaped fracture near to the top surface of the borided steels. The height of the half-cone-shaped fracture as a function of the cross-sectioned scratch loads was used to determine the fracture toughness of the FeB and Fe₂B layers. The results showed a fracture resistance of \(\sim2.8\,{\text{MPa}}\sqrt m\) for the FeB layer formed at the surface of borided AISI 1045 steel. Likewise, the effect of the DAP on the surface of the borided AISI 1045 steel promoted the formation of an exclusively Fe₂B layer, with an increase in the fracture toughness of the whole boride layer around \(5\,{\text{MPa}}\sqrt m\). Finally, the principle of the technique can be used to minimize the influence of the anisotropic properties on the fracture toughness along the depth of boride layers.     

Characterization of borided pure molybdenum under controlled atmosphere

In this study, the structural characterization and boriding kinetics of the molybdenum borides formed on the surface of borided pure molybdenum (Mo) have been investigated. Boronizing was carried out in solid medium with boron component forming Ekabor ® 2 (90% SiC, 5% KBF₄, 5%B₄C) powders at 1273 K, 1373 K for 2, 4, 6, 8 hours under a controlled atmosphere containing argon gas flow. The boride layer was characterized by the scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Energy dispersive spectroscopy (EDS) and Vickers microhardness tester. X-ray diffraction analysis showed that the boride layers on molybdenum consisted of MoB and Mo₂B phases. However, the MoB phase was observed at certain boriding temperature and boriding times. The thickness of boronized layers almost ranged from 12 to 42.5 μm with boriding time. A parabolic relationship was observed between boride layer thickness and boriding time. The growth rate constant and activation energy for the boride layer were calculated. The hardness of borides compounds formed on the surface of molybdenum ranged from 925 to 1150 HV_0.05, whereas the hardness of the untreated molybdenum sample was 258 HV_0.05.     

Role of polyacrylamide concentration on corrosion behavior of N80 steel in the HPAM/H2S/CO2 environment

The effect of polyacrylamide on corrosion behavior of N80 steel in the HPAM/H₂S/CO₂ environment was studied by using weight-loss and electrochemical tests to simulate the environment of production wells in polymer flooding. The morphology and composition of corrosion scales were studied by scanning electron microscopy, energy dispersive X-ray spectrometer, and X-ray photoelectron spectroscopy. The results show that as the polyacrylamide concentration increases, the uniform corrosion rate of N80 steel decreases gradually. The safe service life of N80 steel grows along with the increase of the concentration of polyacrylamide. The corrosion scales of N80 steel in the HPAM/H₂S/CO₂ environment is split into two layers, an inner layer of O-rich composed of FeCO₃ and an outer layer of S-rich consisting of FeS. Polyacrylamide adsorbs on the surface of N80 steel to form a protective network, which blocks contact between the metal and the solution and then inhibits the anodic dissolution of the metal. Moreover, the growth of polyacrylamide concentration increases the pH value of the solution and promotes the ionization of H₂S, HS⁻, and H₂CO₃ in the solution.     

Effects of annealing on elemental composition and quality of CZTSSe thin films obtained by spray pyrolysis

The spray pyrolysis was used for the deposition of Cu₂ZnSn(S, Se)₄ (CZTSSe) kesterite thin films. The basic spray pyrolysis solution was prepared from two precursor solutions containing thiourea and cooled to a temperature near 1°C, which leads to minimizing the number of insoluble hydrates of copper chloride. The optimal substrate temperature was 350°C and the distance from the sprayer nozzle 30 cm. The as-deposited Cu₂ZnSnS₄ layers were annealed in S₂ atmosphere for the compensation of the sulfur deficiency and with the addition of Sn in order to avoid tin loss. Cu₂ZnSn(S, Se)₄ thin films were obtained after the annealing of as-deposited films in the (S₂ + Se₂) atmosphere. The surface morphology and composition of obtained thin films were investigated using the energy dispersive X-ray (EDX) microanalysis and Raman spectroscopy measurements. The structural characterization by the grazing incidence X-ray diffraction (GIXRD) showed the presence of Cu_2–x S phases in all of the annealed thin films. For the Se/(S + Se) ratio of the thin films annealed in the (S + Se) atmosphere was established from EDX measurements and analysis of GIXRD data, the results are in satisfactory agreement.     

Formation of surface layer based on Al3Ti on aluminum by laser cladding and its compatibility with ceramics

Intermetallic compound Al₃Ti or intermetallic compound matrix composite (IMC) surface layers were formed on Al surface by laser cladding. To form sound IMC surface layers, laser conditions must be controlled to suppress the melting of base metal. With increasing the volume fraction of ceramics in the IMC layer, it needed higher laser power to obtain IMC layer although the control of laser conditions became easier. During laser cladding, TiB₂ melted by laser irradiation and then homogeneously precipitated as fine particles at a cooling stage. On the contrary, TiC and SiC hardly melted and were dispersed in Al₃Ti matrix. SiC reacted with Ti to form titanium-silicide or TiC, which made the composition of matrix richer in Al than Al₃Ti and caused degradation of the wear property. IMC surface layer improved the wear property of Al substrate. The particle size as well as volume fraction of dispersoid ceramics affected the wear property.     

Structure of buffer CeO2 and LaNiO3 layers prepared by method of pulsed laser deposition on textured Ni-Cr-W substrates

The results of an investigation of the structure, composition, and topography of the surface of buffer layers of CeO₂, LaNiO₃, and CeO₂ + LaNiO₃ on nonmagnetic textured NiCr_9.2W_2.4 substrates with a cube texture, which were prepared by pulsed laser deposition, are presented. The substrates with a buffer layer of this composition can be of interest for growing thin films and heterostructures of a wide class of oxide compounds, including superconductors of composition YBa₂Cu₃O_{7 ? δ} (123).     

Nanostructuring a steel surface by electrospark treatment with new electrode materials based on tungsten carbide

The effect of the physical and chemical properties of the material of a carbide VK8 alloying electrode with 1–5 wt % Al₂O₃ nanopowder was studied based on the composition, structure, and properties in the modified surface layer upon the electromechanized hardening of steel 35 with varying the frequency and duration of the electrical pulse repetition. The data obtained can serve as a basis for creating devices of a new generation, special electrode materials, and for developing the technologies for nanostructuring the surface layers of metal materials.     

Laser-induced enhancement of the surface hardness of nanoparticulate TiO2 self-cleaning layer

We here report that the abrasion resistance of nanoparticulate TiO₂ self-cleaning layers can be highly enhanced without a considerable loss of photocatalytic capability. TiO₂ coating layers solution-deposited onto the glass substrate were irradiated by a pulsed ultraviolet (UV) laser at 355 nm, which modified the surface morphologies via laser-induced local melting of TiO₂ nanoparticles. The surface hardness, measured by pencil scratch test, improved with increasing laser power (P). While an unmodified TiO₂ layer revealed a hardness of 6B, it increased to 2H after the surface was irradiated at P = 0.3 W. Almost all of the stearic acid deposited on an unmodified sample disappeared after UV exposure for 12 h. The photocatalytic decomposition was slowed down on laser-irradiated TiO₂ surfaces and this is attributed to the reduction of specific surface areas as a result of the morphological modifications. However, a TiO₂ layer hardened to 2H still exhibited fairly good photocatalytic activity, decomposing more than 75% of the stearic acid after exposure for the same duration.     

Establishing multilayered coating on Mo–12Si–8.5 B alloy by Si pack cementation and its oxidation behavior at 900°C–1300°C

A multilayered oxidation protection coating consisting of MoSi₂ outer layer, Mo₅Si₃ internal layer, and Mo₅SiB₂/MoB inner layer was developed on the surface of Mo–12Si–8.5B 1.0 wt% ZrB₂ alloy via Si pack cementation. The multilayered coating significantly enhanced the oxidation resistance of the alloy at 900°C, 1100°C, and 1300°C in the air by exhibiting negligible oxidation recession. MoSi₂ outer layer provided admirable oxidation protection for the alloy at high temperatures by forming a thin and protective SiO₂-rich glass scale on its surface. This was supplemented by the Mo₅Si₃ internal layer and Mo₅SiB₂/MoB inner layer that reduced the thermal expansion mismatch between the MoSi₂ outer layer and substrate, and therefore no obvious cracks were found in the MoSi₂ outer layer. More importantly, the Mo₅SiB₂/MoB layer as an in situ barriers of Si interdiffusion ensured the stable existence of MoSi₂ and Mo₅Si₃ layers without obvious thickness change during oxidation at 900°C and 1100°C. Mechanical property test indicated that the formation of the coating layers could not affect the fracture toughness of the alloy.     

Structure of Al–Ni intermetallic composite layers produced on the Inconel 600 by the glow discharge enhanced-PACVD method

The Plasma Assisted Chemical Vapor Deposition (PACVD) treatment conducted under glow discharge conditions in an atmosphere of trimethylaluminum vapors applied to an Inconel 600 substrate yielded composite surface layers built of intermetallic phases of the Al–Ni system with the outer zone composed of aluminum oxides. Such layers have very advantageous performance properties, such as high hardness, good corrosion and frictional wear resistance and, good adherence to the substrate.The present study is dedicated to microstructure characterization of the layers. The layers were examined using a variety of methods. Based on the results of these examinations, the microstructure of the composite layers was described as a multizone one with an outer Al₂O₃ zone, an intermediate AlNi₃ + Al₂O₃ zone and a diffusion zone of type Ni(Al,Cr,Fe) + AlNi₃ + Cr₇C₃. The mechanism of layer formation as well as the correlation between the microstructure and the observed improvement of the surface properties of the Inconel 600 alloy are discussed.     

Structural and mechanical evaluation of the effect of oxygen boost diffusion on a gamma based titanium aluminide of Ti-45Al-2Nb-2Mn-1B

Air oxidation, vacuum heating and a subsequent oxidation (DT treatment) of Ti-45Al-2Nb-2Mn-1B (at.%) titanium aluminide resulted in several oxide layers and a hard Ti₃Al as an interlayer between the substrate and the oxide layers.Surface characterization was carried out using X-Ray Diffraction (XRD), Glow Discharge Spectroscopy (GDS), electron microscopy, microhardness tests, ball-on-disk tests and profilometry.The compositions of oxides were TiO₂ and Al₂O₃ at the surface layers after final air oxidation and Ti₃Al interlayer was enriched with oxygen.Multi step treatment improved the hardness of treated surfaces significantly in comparison with that of the sample thermally oxidized only at 800 °C (TO treatment). The hard Ti₃Al interlayer containing soluble oxygen supported the top oxide layers of the DT treated sample against indentation. Such supporting layer did not form between the soft substrate materials and the oxide layers of TO treated materials.The mean value and variation of friction coefficient on multi step treated surfaces were less than that of the untreated material. The friction behavior of worn surfaces on the multi step treated material against steel and WC-Co ball sliders was rather smoother than that of TO treated samples.Top surface layers of TO treated material were removed at very shorter sliding distances and lower loads than those of DT treated surfaces against both steel and tungsten carbide sliders.     

CeO2对铝合金表面激光增材制造组织及耐蚀性影响

利用激光增材制造技术,在6063Al基体表面制备了添加不同含量CeO₂的Ni60合金层,并通过金相显微镜、XRD、SEM和电化学腐蚀测试仪等设备进行了分析和测试,研究稀土CeO₂对6063Al表面激光增材制造镍基合金层与基体结合界面处的组织结构及耐腐蚀性能的影响。结果表明,在表面形貌上,4%~5% CeO₂的合金层形貌最好,CeO₂含量低于3%时难以获得表面良好的合金层,CeO₂含量在5%~10%时,合金层表面气孔、脱落等缺陷较少;在截面形貌上,合金层中CeO₂含量在0%~2%时易出现裂纹,含量在5%~10%时主要缺陷为气孔,4% CeO₂+Ni60合金层中无明显气孔和裂纹,具有相对较好的截面形貌;添加4% CeO₂可以改善Ni60合金层的组织结构,促进合金层的晶粒细化和组织分布均匀;添加不同含量CeO₂可以改善铝合金表面Ni60合金层的组织形貌,较佳的稀土添加量是4% CeO₂;在1mol/L H₂SO₄中,CeO₂ Ni60合金层的耐腐蚀性能是Ni60合金层的4.25倍;在3.5% NaCl溶液中,CeO₂ Ni60合金层耐腐蚀性能是Ni60合金层的1.4倍;在1mol/L NaOH溶液中,CeO₂ Ni60合金层的耐腐蚀性是Ni60合金层的1.43倍。     

In situ synthesis and fabrication of tricalcium phosphate bioceramic coating on commercially pure titanium by laser rapid forming

Titanium possesses good mechanical property, but a lack of bioactivity. Bioceramic is usually used to coat the surface of a titanium implant to enhance its bioactivity. Therefore, it is important for the coating to have a high bonding strength to the titanium substrate and contain bioactive phases. In this work, CaCO₃ and CaHPO₄·2H₂O powders were used to fabricate a bioceramic coating on commercially pure titanium (cp-Ti) by the laser rapid forming (LRF) technique. The phase composition of the coating contained 95 wt.% of β-TCP and 5 wt.% of α-TCP. Three layers were found in the coating: a ceramic layer, a transitional layer, and the substrate layer. In the transitional layer, interpenetration of phases was observed. The bonding strength between the coating and the cp-Ti substrate was in excess of 40.17 MPa. In addition, the elastic modulus and the micro-hardness of the coating were 117.61 GPa and 431.2 HV_0.1, respectively. Furthermore, the static immersion test has confirmed that the coating not only prevented the corrosion of cp-Ti, but also induced the redeposition of β-TCP in synthetic saliva.     

X-Ray Photoelectron Spectroscopy of Chemically Deposited Amorphous and Crystalline Ni–B Coatings

The chemical state of elements and the composition of surface and bulk layers of Ni–B coatings with the volume concentration of boron of 3.7 and 27.1 at. % obtained by electroless catalytic reduction are studied with x-ray photoelectron spectroscopy combined with layer-by-layer profile analysis. Up to 90% of nickel and 80% of boron are shown to be reduced on the surface of the coatings. The effect of the conditions of heat treatment in a vacuum and in air on the composition of the surface layer is analyzed. The original nonuniformity of the in-depth distribution of the elements is found to be most of all affected by heating in air at a temperature of 700°C that provides the surface formation of a B₂O₃ oxide layer containing no nickel. A stabilized composition of the alloys is observed at a depth of 10 to 60 nm depending on the conditions of heat treatment.     

Segregation beneath oxide scales

Studies are reported and discussed on Auger analyses of the region beneath Cr₂O₃, Al₂O₃, or NiO layers on their metal substrate. Small concentrations of S, C, and P were detected in areas which had been connected to the oxide layer, most probably due to segregation in defects, such as misfit dislocations, microvoids, grain boundaries, etc. For high oxygen pressures at the interface (Ni–NiO) P also can be enriched in the inner layer as phosphate. Sulfur starts to segregate to the free-metal surface as soon as the scale and metal separate, stabilizing voids and accelerating their growth to cavities or favoring the detachment of scale in the case of growth stresses. In this surface segregation S displaces C and P from the metal surface.