Plasma modification of a protective coating formed by hexamethyleniminem-nitrobenzoate on iron

A layer of hexamethyleniminem-nitrobenzoate was modified in low-temperature plasma on the air-oxidized iron surface. The composition and physicochemical properties of the modified inhibitor was studied by XPES and atomic force microscopy. It was assumed and then justified that the enhanced protective properties of a plasma-treated coating are due to the formation of corrosion-resistant iron nitrides and oxides, as well as new nitrogen- and oxygen-containing organic compounds with better inhibitive and adhesive abilities. Plasma-induced polymerization of the coating results in a high-strength, dense hydrophobic film that seems to be responsible for its enhanced barrier properties.     

Stability of protective oxide films formed on a porous titanium

Porous titanium has mechanical advantages over its solid counterpart, especially for use in surgical implants, however, its corrosion resistance is not as good. The relative stability of various oxide films on both porous and solid titanium was thus investigates. The point of initial failure of the oxide films on porous titanium was found to be within the depths of the pores. It is also postulated that galvanic coupling to the outer surface, via a mechanism akin to crevice corrosion, may promote the rapid dissolution in the pores. Preliminary, results suggest that thermal oxides offer better corrosion protection to porous titanium than anodic oxides.     

Characterization of the alumina scale formed on a commercial MCrAlYHfSi coating

A commercial NiCoCrAlYHfSi coating deposited on a Ni-base superalloy substrate was characterized before and after high temperature oxidation. The combination of Y, Hf and Si additions is reported to improve coating performance. Advanced characterization techniques including scanning-transmission electron microscopy were used to study the segregation behavior of Y and Hf ions to the alumina grain boundaries after 200 h at 1050 °C and 100 and 200 h exposures at 1100 °C. After both exposure times, two distinct oxide layers were observed. The outer transient layer included many Y- and Hf-rich oxide particles. The inner layer consisted of columnar α-Al₂O₃ grains normal to the surface of the coating. Segregation of Y and Hf ions was found on the alumina grain boundaries as has been observed in model alloys with similar compositions. Isothermal exposures for up to 200 h at 1050° and 1100 °C caused a minimal increase in surface roughness. However, 200 1-h cycles at 1100 °C resulted in a more significant increase in surface roughness.     

球墨铸铁表面激光熔覆Fe-Cr-Si-B涂层

在球墨铸铁QT600-3表面激光熔覆铁基合金涂层,分析测试了激光熔覆层的微观组织、显微硬度以及界面处Fe、Cr元素的分布情况。结果表明:激光熔覆区为胞状晶和树枝晶结构,组织均匀致密,Fe、Cr等元素在熔覆层与母材间发生了相互扩散,形成良好的冶金结合,并有硬质点的弥散分布,使得涂层硬度大幅度提高,大约为基体硬度的2.6倍。     

Bioactive modification of titanium by coating bioactive glasses

Two different bioactive glasses, 55SF (55.1SiO₂-3.4P₂O₅-9.2Na₂O-27.8CaO-4.5CaF₂; mol%) and 50SB (50.1 SiO₂-3.4P₂O₅-9.2Na₂O-32.3CaO-5B₂O₃; mol.%), were used to coat titanium metal in order to make it bioactive. The bonding characteristics between titanium substrate and bioactive glass were examined and then the hydroxyapatite formation on the coated specimen was studied after its reaction in a simulated body fluid (SBF). A thin film X-ray diffractometer and scanning electron microscope were employed for the examination of the coated layer surface. Ionic concentrations in the reacted solution were also measured. When the 55SF glass was coated with a ground coat, a Ti₅Si₃ crystal was formed at the interface between the titanium and the glass coat. There was no hydroxyapatite found on this layer when reacted in a SBF. 50SB glass was used as a cover coat and fired at various temperatures. An amorphous phase was observed when fired at 800°C, while oxyapatite crystal was obtained when fired at 900°C. When those samples were reacted in a SBF, hydroxyapatite crystal was deposited only on the sample that had an amorphous phase.     

A protective coating of Silicate on zincplate

A protective chemical conversion coating, developed on zincplate from a silicate aqueous solution, was found to be more effective in anticorrosive performance than molybdate, tungstate and some heteropoly acid conversion coatings. The relative atomic percent content (A.C. %) of the film, obtained from the constant elemental composition region of the AES profile curves, were oxygen 59.2 zinc 5.9% silicium 19.1%, nitrogen 2.7%, sulfur 4.2%, phosphorus 3.6% and carbon 5.3%. The results of XPS analysis showed that zinc existed as zinc sulfide in the surface layer of the film, while as zinc oxide in the internal layer of the film.     

Study on microstructure of Fe-Cr-C-Ni-B-Si coating formed by plasma jet surface metallurgy

The technical connotation of surface metallurgical technology by DC-Plasma-Jet is a kind of rapid, non- equilibrium metallurgical process which is similar to powder metallurgy. Accordingly the specialized equipment is developed all by ourselves, which is not subjected to limitation of solubility, melting point, density of constituents, therefore pre-alloy powders are not needed. The plasma surface metallurgical coating using Fe-Cr-C-Ni-B-Si mixed alloy powders has good wettability with substrate material. The metallurgical coating has apparent characteristics of rapid and layered crystallization from planar crystal-cell to dendritic transition zone at the interface, from dendritic crystal to equiaxed crystal in the midst, from equiaxed crystal to spike crystal on the surface. Its metastable microstructure is complex phase of supersaturated γ- （ Fe, Ni ） dendritic crystal solutioning great amount of alloy element and interdendritic eutectic structure （ Cr, Fe） γ （ C, B） 3 and T-（Fe,Ni）.     

LY12铝合金微弧氧化/树脂填料复合涂层的组织与防热性能

为提高LY12铝合金的隔热与抗火焰烧蚀性能,采用微弧氧化及涂覆复合工艺在其表面制备了底层微弧氧化/外层树脂填料复合涂层。用自制隔热装置及氧-乙炔烧蚀装置分别评价涂层的隔热与抗烧蚀性能。隔热测试表明试样暴露在450℃恒温6 min时,微弧氧化/莫来石空心微球树脂复合涂层隔热温度为245℃。微弧氧化/微球树脂复合涂层在2200℃氧-乙炔火焰下烧蚀持续25 s,质量烧蚀率为0.0425 g.s-1,线烧蚀率为0.0478 mm.s-1,复合涂层烧蚀区域背面均无变化,烧蚀条件下微弧氧化/微球树脂涂层隔热温度为1859℃,其隔热性能与450℃静态隔热测试结果一致。铝合金表面微弧氧化/树脂填料复合涂层表现出优异的隔热与抗烧蚀性能。     

One-step modification of nano-hydroxyapatite coating on titanium surface by hydrothermal method

Since metallic biomaterials used for orthopedic and dental implants possess a paucity of reactive functional groups, bioactivity modification of these materials is challenging. To enhance osteoconductivity, sandblasted and acid etched titanium (SLA-Ti) discs were hydrothermally treated in simple suspension of hydroxyapatite (HA) by a one-step method in the present work. Change of surface chemistry, surface morphology of samples, and structure of formed nano-HA were investigated by X-ray photoelectron spectrometry (XPS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The results demonstrated that the concentration of hydroxyl groups increased after hydrothermal treatment. The ability of the titanium surface to form nano-HA was enhanced by increasing the hydrothermal treatment temperature and time. The bonding strength of the formed nano-HA coating, examined by an ultrasonic cleaning process, was higher than that of HA coating generated directly by HA suspension deposition. Culturing of MC3T3-E1 cells on the SLA-Ti and HT-Ti discs in vitro showed that HT-Ti was more favorable for cell attachment and differentiation than SLA-Ti. Hence the one-step hydrothermal treatment with HA suspension was a simple, effective and promising method for HA coating modification of titanium implants.     

锆合金表面微弧氧化陶瓷膜制备及特性分析

采用交流微弧氧化方法在一种锆合金表面制备出保护性陶瓷膜。采用SEM、EDS、XRD分析了陶瓷膜的表面形貌、截面组织、成分和相组成,并测量了微弧氧化前后锆合金的极化曲线,以评估陶瓷膜的电化学腐蚀特性。结果表明,膜层较为致密,并与锆合金结合良好。陶瓷膜由m-ZrO2、t-ZrO2、S iO2相所组成,其中S iO2相主要分布在外层膜里。微弧氧化处理后,锆合金的腐蚀电位上升,腐蚀电流密度下降,它的抗腐蚀能力得到较大提高。     

铸铁等离子熔覆铁基合金耐磨涂层

利用等离子熔覆技术,选择合适的工艺参数,在硼铸铁基体上熔覆铁基合金粉末制备具有冶金结合的耐磨涂层.采用金相显微镜、X射线衍射仪、扫描电镜研究了涂层的组织,利用显微硬度计测试了涂层的显微硬度,通过环-块磨损试验评估了涂层的耐磨性.结果表明,硼铸铁等离子熔覆铁基合金涂层组织主要由(Cr,Fe)7C3,α-(Fe,Cr)和Fe3C相组成;涂层的显微硬度可达600～1 200 HV0.2;在干滑动磨损条件下,涂层的耐磨性约是基体试样的5倍.涂层中高硬度的(Cr,Fe)7C3及Fe3C相的抗磨骨架作用,大量Cr,Si原子溶入基体引起的过饱和固溶强化作用,涂层快速加热及快速凝固产生的细晶强化作用是涂层耐磨性提高的主要原因.     

铸铁表面等离子熔覆Fe-Cr-Si-B涂层的组织特征

利用常压弧光等离子体在铸铁表面熔覆Fe-Cr-Si-B合金粉末制备耐磨涂层,采用金相显微镜、扫描电镜、X射线衍射仪、显微硬度计对熔覆层的组织和性能进行了分析.结果表明,熔覆层组织主要由近似于六方形、U形、L形或H形的初生(Cr,Fe)7C3相及短杆状或小块状(Cr,Fe)7C3共晶碳化物、,cr)和Fe3C组成;熔覆层与基体界面形成细小的共晶莱氏体组织,在界面处熔覆层与基体中的合金元素发生了相互扩散,形成具有冶金结合的涂层;熔覆层显微硬度可达600～1200HV0.2.     

Structure and properties of the fusion zone formed due to electron beam facing of a coating from nitrogen-alloyed chromium-manganese iron on low-carbon steel

The structure, properties, and residual stresses in the fusion zone formed due to electron beam facing of a wear-resistant coating from chromium-manganese iron with nitrogen-alloyed austenitic matrix on thin-wall articles fabricated from low-carbon steel are studied. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 19–22, February, 2007.     

Aluminization of high purity iron by powder liquid coating

A new powder liquid coating method is proposed for the aluminization of Fe. Mixed powder slurries of Al + Ti or Al + Al₂O₃ are pasted onto Fe specimens, and the specimens are then dried and heated in a vacuum. Unlike hot dipping or powder pack cementation, this technique can be used to aluminize specimens selectively without the need for special equipment or halides. The amount of Al adhering to the substrate is determined by the Al–Ti reaction or coalescence of molten Al in Al₂O₃ powder during heat treatment. The Al concentration profile of the modified layer can be controlled by adjusting the powder mixing ratio or heat treatment conditions. The properties of the modified layer are analyzed using a new formulation, where the diffusion equation is treated numerically with consideration of the concentration dependence of the interdiffusion coefficient. The calculated profiles are stable and in good agreement with the experimental data.     

Preparation of one-dimensional polymer films by modification of a hydroxymethylbenzene self-assembled monolayer on iron with alkyltriethoxysilanes for preventing iron corrosion

A self-assembled monolayer (SAM) of p-hydroxymethylbenzene HOCH₂C₆H₄ - (HOMB) moiety adsorbed on iron by the formation of a covalent bond between carbon and iron atoms was prepared by electrochemical derivatization of an iron electrode with p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH₂C₆H₄N₂BF₄. The electrode covered with the HOMB SAM was modified with alkyltriethoxysilanes C_nH_2n+1Si(OC₂H₅)₃ (C_nTES, n = 8 or 18) to prepare a film of one-dimensional polymer. The protective ability of the polymer film was determined by polarization measurement of the covered electrode in an aerated 0.5 M NaCl solution. The ability was enhanced by modification of the HOMB SAM with C_nTES markedly. The iron surface coated with the one-dimensional polymer film of the HOMB SAM modified with C₈TES was characterized by contact angle measurement and FTIR reflection and X-ray photoelectron spectroscopies. The persistence in the protective ability of the polymer film against iron corrosion in 0.5 M NaCl may be associated with the strong adsorption via the covalent bond, revealed by electron-probe microanalysis.     

TiB2 coating formed on nickel substrates by electroplating in molten salt of fluoride

The TiB2 coatings deposited over nickel substrate by electroplating was investigated, which is in molten salt of a fluoride mixture involving KF, NaF, K2 TiF6 and KBF4. Effects of temperature, cathodic current density (Jc) and duration on the coating's formation were examined. The composition, morphology and structure of the coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray detector (EDS) and X-ray diffraction (XRD). The results show that the coatings, with black, smooth and uniform appearance, are composed of predominating TiB2 and small amounts of nickel titanium oxide (Ni0.75 Ti0.125 O). The coatings show a nodular morphology and the grain size is dependent on the Jc and ranges about 1 - 10 μm. There is a linear relationship between the coating's thickness and the time of electrolysis within certain duration range. The reduction of the potassium can take place simultaneously with the electrochemical synthesis of TiB2 as the Jc is in excess of certain level. The hardness of the TiB2 coatings is likely to be deteriorated due to the presence of potassium and Ni0.75Ti0.125 O in the coatings.     

微弧离子沉积阻燃涂层及其性能

采用微弧离子表面改性技术在TC11合金表面制备阻燃涂层,采用扫描电镜、透射电镜、XRD等方法分析了阻燃涂层组织及物相,采用“钛火”液滴法试验平台测试了TC11钛合金在300～700 ℃之间的燃烧参数,验证了同等试验条件下带有阻燃涂层TC11钛合金试样在300～700 ℃之间的阻燃有效性. 结果表明,制备的阻燃涂层主要由TiZr非晶相组成,涂层致密,与基体为冶金结合,700 ℃以内具有一定的阻燃性能,分析阻燃涂层的阻燃机理主要为涂层吸收能量,减小基体对热量的吸收,同时阻止钛合金与氧接触机制来阻燃.     

Nb对送粉激光熔覆层组织和性能的影响

研究了送粉激光熔覆铁基合金添加Nb粉的可能性,并对熔覆试样进行了显微组织分析和硬度、磨损性能测试.扫描电镜、光学显微镜、能谱分析和x射线衍射分析结果表明,Nb在熔覆层中均匀分布,Nb的加入使枝晶组织明显细化,界面上方等轴晶数量增多,共晶组织更加致密.硬度测试和磨损试验表明,Nb元素的加入提高了熔覆层的显微硬度、耐磨性.分析认为,组织与性能的提高是由于Nb的加入生成大量弥散均匀分布的NbC颗粒增强相,同时生成的NbC成为异质核,提高了凝固结晶过程中的形核率,并且Nb原子优先占据晶界,强化了晶界,阻碍了晶体的长大.