Influence of hydrothermal temperature on hydroxyapatite coating transformed from monetite on HT-C/C composites by induction heating method

Hydrothermal post-treatment was used to convert monetite coating fabricated by induction heating method on H₂O₂ treated C/C (HT-C/C) composites to an adherent HA coating. The monetite coatings were hydrothermally treated for 4 h at 373 K, 403 K, 423 K, and 453 K in a 50 mL autoclave. After hydrothermal post-treatment, the structure, morphology and the chemical composition of these HA coatings were characterized with XRD, FTIR SEM and EDS. A scratch test was conducted to measure the strength of the adhesion of the coatings to the HT-C/C substrate. The results showed that the degree of crystallinity and the Ca/P ratio of the HA coatings increased with increasing hydrothermal temperature. The submicron-level morphology and adhesion of the HA coatings were highly affected by the hydrothermal temperature. From the results, it can be suggested that 423 K was the best hydrothermal treatment temperature for the HA coatings which were transformed from the monetite coatings produced by the induction heating method on HT-C/C composites.     

CVD温度对钽沉积层性能的影响

介绍了化学气相沉积(CVD)制备难熔金属钽涂层的原理及方法。采用冷壁式化学气相沉积法,在钼基体上沉积出难熔金属钽层。分析研究了CVD温度对沉积层的沉积速率、组织、结构和硬度等的影响。结果表明:在1000～1200℃温度范围,沉积速率随温度升高而增大;当温度超过1200℃时,沉积速率随温度的升高反而略有减小;沉积层组织呈柱状晶并随温度的升高逐渐增大;沉积层的硬度及密度随温度的升高而逐渐降低。化学气相沉积钽的最佳温度在1100℃左右。     

Effect of Substrate Temperature on Cold-Gas-Sprayed Coatings on Ceramic Substrates

This study focuses on cold-gas-sprayed deposition of metallic coatings onto ceramic substrates for application in power electronics. In order to achieve the required surface activation for bonding, the substrate is heated during spraying. The effects of substrate temperature on bond strength and coating properties are investigated for cold-gas-sprayed coatings of copper and aluminum on Al₂O₃. It is found that the adhesion strengths of the cold-gas-sprayed coatings and that of the single-impacting particles increase with the increasing temperature and roughness of the substrate. Coatings sprayed on heated substrates show relatively low compressive stresses and low hardness, while their electrical conductivity reaches high values of over 90% IACS. Overall, a higher substrate temperature is found to improve the coating properties significantly.     

炭/炭复合材料声电沉积钙磷生物活性涂层的生长机理

通过声电沉积在炭/炭复合材料表面制备钙磷生物活性涂层,采用SEM（带EDAX）,XDR,FTIR研究电沉积时间对钙磷生物活性涂层的形貌、结构和组成的影响.实验结果表明：沉积初始先在炭/炭表面形成无定形层,片状磷酸氢钙（DCPD）在其表面生长,随着电沉积时间的延长,逐渐向针状的羟基磷灰石Ca10（PO4）6（OH）2（HA）转变,涂层厚度和n（Ca）/n（P）不断增加,涂层的结晶度和电解液的pH值下降.涂层为缺钙磷灰石.同时探讨了在炭/炭复合材料表面钙磷生物活性涂层的生长机理.     

Mechanical Properties and Dissolution Behavior of Plasma Sprayed Wollastonite Coatings Deposited at Different Substrate Temperatures

The effect of substrate temperature on the microstructure, mechanical properties and dissolution behavior of wollastonite coatings is investigated. The crystallinity of as-deposited coatings increases with increasing substrate temperature, whereas the porosity shows only a little variable tendency. The Knoop hardness and elastic modulus increase with the substrate temperature up to 400?°C firstly, and then a decrement is observed with the temperature further increasing to 600?°C. The dissolution rate characterized by the pH changes and the ion concentration changes of Ca, Si and P in SBF decreases with the increase in the substrate temperature. It can be concluded that increasing the substrate temperature is a feasible method to improve the mechanical properties and to decrease the dissolution rate of wollastonite coatings. However, the bioactivity of coatings deposited on preheated substrates is superior to those on non-preheated ones, which presumably results from their different phase compositions.     

生物医用类金刚石薄膜的力学性能评价

用射频等离子体增强化学气相沉积在钛合金表面制备类金刚石薄膜,利用原子力显微镜、纳米力学探针、划痕仪、滑动摩擦和微动摩擦等研究了涂层的表面形貌和力学性能。结果表明：随涂层厚度的增加,表面粗糙度先增后降,最后趋于稳定,硬度和划痕临界载荷提高,室温空气条件下的滑动摩擦系数减小;对于确定的膜厚,随相对湿度增加,摩擦系数降低,这有利于其在体液环境中的应用。     

A critical review of diamond like carbon coating for wear resistance applications

In recent years innovation in carbon based materials have encouraged both researchers as well as industrialists to develop materials/composites with improved tribological properties. Researchers have been fascinated to develop diamond like carbon (DLC) or carbon nanotubes (CNTs) reinforced coatings to their good corrosion resistance, excellent wear resistance, good adhesion strength, and self -lubricious nature. The present review article is mainly focused on various techniques employed in order to process DLC/CNTs coatings as well as provide a summary of DLC/CNTs deposition on different substrates. The present study includes major types, properties and tribological behavior of carbon based materials and mechanisms involved in coating deposition. The study also discusses that deposition of DLC/CNTs coatings on the substrate materials enhances the wear, corrosion and mechanical properties of the substrate.     

灯丝／基体距离对金刚石涂层质量的影响

热丝CVD法金刚石膜生长中基体温度对金刚石薄膜的质量有很大的影响,而基体与灯丝的距离决定着基体沉积温度的高低。本实验采用单一变量法,在其它工艺参数不变的情况下,研究不同基体与灯丝距离对CVD金刚石涂层的质量的影响。采用扫描电镜、Raman光谱、洛氏硬度计对试样的表面形貌、成分和涂层与基体的结合力进行泓定。结果表明,当采用两步法基体预处理,在碳源体积浓度为2％、沉积气压为3kPa、反应功率为4kW时,得到最优金刚石涂层质量的热丝与基体的距离为5mm。     

Stress relaxation through thermal crack formation in CVD TiCN coatings grown on WC-Co with different Co contents

TiCN coatings were grown by chemical vapor deposition (CVD) on WC-Co substrates with different Co contents, in order to control thermal stress. The driving force for the development of thermal stress is attributed to the difference between room and deposition temperature (ΔT ≈ −780 °C), and the mismatch of the coefficient of thermal expansion (CTE) between substrate and coating. Co contents of 6, 7.5, 10, 12.5, and 15 wt% were utilized to adjust the CTE of the substrate, and therefore tune the stress in TiCN coatings. Dilatometry of the substrates and high temperature X-ray diffraction of a powdered TiCN coating indicate a decreasing CTE-mismatch for increasing substrate Co contents. In consequence, residual stress in TiCN determined by X-ray diffraction increases up to 662 ± 8 MPa with decreasing Co contents down to 10 wt%. For Co contents below 10 wt%, the residual stress decreases. The formation of thermal crack networks in TiCN, analyzed by scanning electron microscopy, coincides with 10 wt% Co. Stress relaxation in TiCN coatings through the formation of thermal cracks becomes evident. A finite element simulation utilized for the calculation of residual stress distributions reveals shielding effects, which occur with the introduction of thermal cracks. Discrepancies between experimental and simulated thermo-elastic stresses imply the presence of secondary relaxation sources. High temperature residual stresses in TiCN, determined up to 1000 °C (i.e. above deposition temperature), suggest additional thermal crack formation for substrate Co contents of 6 wt%.     

沉积温度对高性能TiAlN涂层微观结构和力学性能的影响

采用真空电弧离子镀（AIP）技术在不同沉积温度下TiAlN涂层,用于高性能制造,并研究了沉积温度与表面性能的关系。结果表明,由于离子轰击作用,表面大颗粒随沉积温度的升高而减少。随着沉积温度的升高,涂层表面的晶粒尺寸先急剧减小后逐渐增大。此外,沉积温度对合成涂层的相组成和化学成分影响不大。随着沉积温度的升高,硬度和粘结强度先迅速增加,后逐渐降低。当沉积温度在450℃左右时,沉积的TiAlN涂层硬度最高,粘结强度最大。上述现象的发生机理与沉积过程中表面与界面之间的微观组织和残余应力的变化有关。合成的涂层在高达900℃的空气中具有良好的热稳定性。     

Preparation of calcium phosphate coatings on Mg-1.0Ca alloy

The calcium phosphate coatings were prepared by virtue of electrochemical deposition in order to improve the corrosion resistance of Mg-1.0Ca alloys in simulated body fluids.The chemical compositions,structures and morphologies of the coatings were investigated by energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and scanning electron microscopy(SEM), respectively.The potentiodynamic electrochemical technique was employed to investigate the bio-degradation behavior of Mg-1.0Ca alloys with Ca-P coatings in Hank's solutions.The experimental results show that the deposited coatings predominately consist of flake-shape brushite(DCPD,CaHPO4·2H2O)crystallites.The corrosion resistance of the substrates with coatings is improved in Hank's solutions significantly.     

Friction surfaced tool steel (H13) coatings on low carbon steel: A study on the effects of process parameters on coating characteristics and integrity

Tool steel H13 was friction surfaced on low carbon steel substrates. Mechtrode (consumable rod) rotational speed and substrate traverse speed were varied, keeping the axial force constant. The effects of process parameters on coating characteristics and integrity were evaluated. A process parameter window was developed for satisfactory deposition of tool steel coatings. Coating microstructures were examined using optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microhardness tests, shear tests, and bend tests were conducted on coatings. The results show that coating width is a strong function of mechtrode rotational speed, while coating thickness is mainly dependent on substrate traverse speed. Lower mechtrode rotational speeds results in wider coatings, while higher substrate traverse speeds produce thinner coatings. Thinner coatings exhibit higher bond strength than thicker coatings. Coatings show no carbide particles, yet exhibit excellent hardness (above 600 HV) in as-deposited condition due to their martensitic microstructure.     

Electrochemical deposition of hydroxyapatite coatings on titanium

1 Introduction Titanium implants have been used widely for various types of bone-anchored reconstructions due to their excellent corrosion resistance and mechanical properties. However, titanium exhibits poor osteoinductive properties, fortunately, which…     

Nitrogen Contents on Tribological Properties of Magnetron Sputtered SICN Coatings

SiCN COATINGS have stimulated wide interestbecause they exhibit many good properties for potentialindustrial applications,such as high opticaltransparency in Infrared(IR)region,wide bandgap,chemical inertness and high refractive index,goodinsulating property,good mechanical and tribologicalproperties(high hardness,elastic modulus,low friction,etc.)[1-4].Amorphous and/or hydrogenated SiCNcoatings can be prepared by various depositionmethods,such as laser ablation[5],plasma-assistedchemica…     

微束等离子喷涂NiCrBSi涂层

采用微束等离子喷涂方法在St37低碳钢上制备了NiCrBSi涂层.研究了基材温度、等离子气体流量、喷涂距离和电流强度等工艺参数对涂层组织结构和性能的影响.采用光学显微镜观察涂层的组织结构,用Perthometers M4P 150测定涂层的表面粗糙度,以及用LECO TC316气体抽提仪检测涂层的氧含量.结果表明,在试验条件下,喷涂参数对涂层组织和性能产生较大的影响.随着电流和基材温度的增加涂层的粗糙度降低,涂层的氧含量随着基材温度和喷涂距离的增加而增加.大多数涂层的显微硬度大于600 HV0.2.尽管粒子速度较低,涂层的平均结合强度仍然大于50 MPa.     

Investigation of Deposition Behavior of Cold-Sprayed Magnesium Coating

Two types of magnesium powders with different particle size distributions were deposited by cold spraying at different main gas temperatures. The effects of gas temperature and particle size distribution on the deposition efficiency of particles were studied. The microstructure of coatings was observed, and the porosity of coatings was evaluated. The deposition efficiency of particles increased, and the porosity of coatings decreased with the increase of gas temperature. The deposition efficiency of particles increased when using the powder with a smaller particle size distribution. Stainless steel and aluminum plates were used as substrates. The bonding strength and mechanism between the coating and substrate were studied. The commercial finite element software ABAQUS was used to help us better understand the deformation behavior of particles and substrates. The mean bonding strength slightly increased when aluminum plates were used as substrates. The bonding mechanism of Mg coatings on stainless steel and aluminum substrates was discussed.     

The effect of plasma spraying power on the structure and mechanical properties of hydroxyapatite deposited onto carbon/carbon composites

This paper deals with the effect of plasma spraying power on hydroxyapatite (HA) coatings on carbon/carbon composites (C/C composites). The microstructure and phase composition of the as-sprayed coatings have been examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The shear strength of the HA coatings–C/C substrates was detected on a RGD-5 tensile testing machine. Results indicate that the melting extent and the shear strength of the coatings were evidently improved with the increasing of spraying power. Moreover, the amount of decomposed phases is increased and the content of crystalline HA of coatings was slightly changed. Observation of fracture surfaces shows that carbon fiber bundles can bond well with HA coatings using 40 kW spraying power.     

Deposition of alpha-WC/a-C nanocomposite thin films by hot-filament CVD

Nanostructured tungsten carbide coatings containing amorphous carbon (a-C) phases are interesting composite materials. The incorporation of the a-C phase simultaneously improves the thermal stabilization of the carbide phase and the coatings' friction coefficient. Such nanocomposite coatings are also electrically conducting with resistivity values comparable to the transition metals, which make them useful for a number of electrochemical and electronic applications. Many deposition techniques have been used for the synthesis of these coatings. However, most of them lead to the formation of complex crystalline structures consisting of more than one carbide phase and varying amorphous contents.The novelty of this work is the formation of WC coatings with controllable film thickness and a-C content, almost fully composed by α-WC phase. Tungsten carbide coatings were deposited on silicon substrates using a hot filament chemical vapor deposition (HFCVD) equipment with hydrogen and methane as the deposition gasses. Two types of nanocomposite coatings were obtained with significant variations of the carbide phase and a-C contents.The results point to the W vaporization time as the main parameter influencing the film thickness. We also conclude that the formation of α-WC phase is the combining result of W filaments vaporization in vacuum and the carbon incorporation at low substrate temperature. The small crystallite size of the carbide grains (5-6 nm) could also explain the rapid diffusion of C through the tungsten-containing layer. Preliminary results show that the amount of a-C incorporated in the film is not only dependent on the CH₄/H₂ ratio but also on the substrate temperature.     

碱液处理诱导钛合金基体表面沉积磷灰石层

改变碱液处理条件和基体材料,考察了这些参数对钛合金诱导磷灰石能力的影响。结果表明：经过碱液处理钛合金表面形成了多孔网状,带负电荷的二氧化钛水凝胶层,在过饱和的模拟体液中可沉积出骨状磷灰石层;随碱液浓度、温度和处理时间境加,凝胶层的孔径和厚度增加,诱导形成磷灰石的能力增强;不同基体材料的诱导能力为：Ｔｉ〉ＴＣ４,Ｔｉ７５〉ＴｉＺｒ。太合金碱液处理后可在模拟体液中沉积出磷灰石层,因此碱液处理使钛合金表     

TC4钛合金微弧氧化膜层高温氧化性能研究

利用微弧氧化(MAO)技术在TC4钛合金表面原位制备陶瓷膜层,并通过硅酸钠水溶液对膜层进行了封孔处理。采用X射线衍射仪(XRD)分析了膜层相组成,通过扫描电子显微镜(SEM)观察了膜层表面形貌。通过粘结拉伸测试,比较了膜层在封孔前后与基体的结合强度。利用高温氧化实验,考察了TC4基体及膜层试样封孔前后的抗高温氧化性能。结果表明:微弧氧化膜层与基体间的结合强度较高,经封孔处理及高温氧化100 h后,膜基结合强度降低至4.29 MPa。与TC4基体相比,微弧氧化膜层的高温氧化增重量小,抗高温氧化性能得到了显著的提高。封孔处理提高了微弧氧化膜层的致密性,使其能更好地阻止氧透过膜层向基体内侵入,进一步提高了膜层的抗高温氧化性能。