激光熔覆Cr3C2/Fe复合涂层的组织与磨损性能

采用5kWCO2连续激光器在低碳钢表面激光熔覆Fe基合金涂层（Fe55）及添加20%Cr3C（2质量分数）的Fe基合金复合涂层（Cr3C2/Fe）,研究了两种涂层的组织结构、显微硬度及耐滑动磨损性能。结果表明,Fe55涂层以亚共晶方式结晶,在初生柱状固溶体枝晶间存在大量的网状共晶组织。Cr3C2/Fe涂层中Cr3C2大部分溶解,原Fe55涂层中初生柱状固溶体枝晶产生等轴化,枝晶组织也明显细化。激光熔覆Fe55涂层主要由α-Fe和Cr23C6组成,Cr3C2/Fe涂层的主要组成相为γ-Fe;α-Fe,Cr23C6以及未熔Cr3C2。激光熔覆Cr3C2/Fe涂层的硬度和耐磨性明显优于Fe55涂层。     

陶瓷/金属复合耐磨涂层的性能评价

应用大气等离子喷涂（APS）技术制备陶瓷／金属复合耐磨涂层试样，并对其硬度，结合强度，微观结构和耐磨性等性能进行评估，结果表明Al2O3-TiO复合涂层在耐磨性方面好于WC－NiCrAl复合涂层，而WC－NiCrAl复合涂层在结合强度性能上好于Al2O3-TiO2复合涂层。     

Corrosion Behavior of Plasma Transferred Arc Fe-based Coating Reinforced by Spherical Tungsten Carbide in Hydrochloric Acid Solutions

Fe-based coatings reinforced by spherical tungsten carbide were deposited on 304 stainless steel using plasma transferred arc(PTA) technology.The composition and phase microstructure of the coatings were evaluated using scanning electron microscopy(SEM),energy dispersive spectrometer(EDS) and X-ray diffraction(XRD).The corrosion behaviors of the coatings in 0.5 mol/L HCl solution were studied using polarization curve and electrochemical impedance spectroscopy(EIS) measurements.The experimental results shows that the tungsten carbide improves the corrosion resistance of the Fe-based alloy coating,but increase in the mass fraction of tungsten carbide leads to increasing amount of defects of holes and cracks,which results in an adverse effect on the corrosion resistance.The defects are mainly present on the tungsten carbide but also extend to the Fe-based matrix.The tungsten carbide,acting as a cathode,and binding material of Fe-based alloy,acting as an anode,create a galvanic corrosion cell.The binding material is preferentially corroded and causes the degradation of the coating.     

Abrasive wear behaviors of high velocity arc sprayed iron aluminum composite coatings

The High Velocity Arc Spraying （HVAS） technology was used to prepare Fe-Al composite coatings by the adding of different elements into cored wires to obtain different Fe-Al coatings. The added compounds do great effect on the properties of the composite coatings. The microstructures and abrasive wear performances of the coatings were assessed by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, and THT07-135 high temperature wear equipment. It was found that the adding of Cr3C2 can greatly increase the room temperature wear behavior, and Fe-Al/WC coatings have adapting periods at the beginning of wear experiment. With the rise of temperature, the wear resistance of Fe-AI/Cr3C2 coatings becomes bad from room temperature to 250℃, and then stable from 250℃ to 550℃; the wear resistance of Fe-Al/WC becomes well with the rise of temperature. The adding of Cr and Ni can also improve wear performances of Fe-Al composite coatings.     

Effect of laser remelting on the microstructure and corrosion resistance of plasma sprayed Fe-based coating

Fe-based amorphous and nanocrystalline coatings were fabricated by air plasma spraying. The coatings were further treated by laser remelting process to improve their microstructure and properties. The corrosion resistance of the as-sprayed and laser-remelted coatings in 3.5wt% NaCl and 1 mol/L HCl solutions was evaluated by electrochemical polarization analysis. It was found that laser-remelted coating appeared much denser than the as-sprayed coating. However, laser-remelted coating contains much more nanocrystalline grains than the as-sprayed coatings, resulting from the lower cooling rate in laser remelting process compared with plasma spraying process. Electrochemical polarization results indicated that the laser-remelted coating has great corrosion resistance than the as-sprayed coating because of its dense structure.     

Effects of heat-treatment on crystallization and wear property of plasma sprayed Fe-based amorphous coatings

The Fe-based amorphous coatings were produced by air plasma spraying. The as-sprayed coatings were heat-treated at the temperature of 573, 873, and 1 023 K, respectively. The crystallization and wear behavior of the heat-treated amorphous coatings were investigated. It was found that the amorphous-nanocrystalline transformation appeared when the as-sprayed coatings were treated at 853 K. The crystallization process had completed and a coating with microcrystallines was formed when the treatment temperature reached 1 023 K. The resultant amorphous and nanocrystalline composite coatings exhibited superior wear resistance compared to crystalline coating. It is attributed to fine grain strengthening of formed nanocrystallines.     

Effect of electromagnetic stirring on the microstructure and wear behavior of iron-based composite coatings

The effect of electromagnetic stirring on the microstructure and wear behavior of coatings has been investigated. A series of iron-based coatings were fabricated by the plasma-transferred arc cladding process by applying different magnetic field currents. The microstructure and wear resistance of the composite coatings were characterized by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and wet sand rubber wheel abrasion tester. The experimental re- sults showed that the microstructure of the coatings was mainly the γ-Fe matrix and (Cr, Fe)7C3 carbide reinforced phase. The coatings were metallurgically bonded to the substrate. With increasing magnetic field current, the amount of the block-like (Cr, Fe)7C3 carbide reinforced phase increased at first, reached a local maximum, and then decreased sharply. When the magnetic field current reached 3 A, the block-like (Cr, Fe)7C3 carbides with high volume fraction were uniformly distributed in the matrix and the coating displayed a high microhardness and an excellent wear resistance under the wear test condition.     

Q235钢表面硬质合金喷涂层的磨损特性研究

用超音速火焰喷涂方法在Q235钢表面进行了WC硬质合金粉末的喷涂.在MRH-5A型滑动磨损试验机上,对涂层进行室温下的干滑动摩擦磨损性能测验,借助于扫描电镜观察磨损试样磨面形貌.通过对摩擦磨损数据进行分析,结果表明：Q235钢表面用WC硬质合金喷涂后,耐磨性大大提高,涂层磨损机理主要表现为磨粒磨损和粘着磨损.     

稀土元素镧和锶对镍基钎焊料焊接性能的影响

碳化钨(WC)复合涂层是一种高温下使用的有效耐磨蚀保护涂层.在BNi-2钎料粉末中添加稀土粉末,用机械合金化技术制备了改进的BNi-2钎料粉末,并在Q235钢基体上制备了碳化钨复合涂层;采用SEM观察了涂层显微组织,分析了稀土元素La和Ce对钎料焊接性能的影响规律.结果表明,在BNi-2合金中分别加入0.1 Wt.%稀土元素La,0.05 Wt.%稀土元素Ce,并采用机械合金化制备的粉状镍基焊料,与母材润湿性良好,焊接性能有所提高.采用此焊料及渗透钎焊技术可以制备出界面结合良好的WC复合涂层.     

灰口铸铁等离子热喷焊WC/Ni基涂层组织和性能研究

在HT250表面采用等离子喷焊工艺制备了碳化钨/镍基合金复合涂层,并对涂层的宏观形貌、微观组织和显微硬度进行了分析.结果表明：复合涂层与基体形成冶金结合,其中WC均匀地分布在涂层的中底部,而在WC附近形成了强化相Fe3W3C,涂层的耐磨性得到了改善;界面处的HT250在快速冷却过程中,发生淬火反应,部分转变为马氏体;涂层的显微硬度在570～870HV0.2之间,明显高于基体硬度.     

喷涂工艺对陶瓷/金属自反应复合涂层组织的影响

用等离子喷涂的方法喷涂自制的Fe2O3 Al自反应复合粉,在金属表面制备了陶瓷-金属多相自反应复合涂层．研究了复合粉和涂层的微观结构,以及喷涂工艺参数对复合粉反应程度及涂层组织的影响．研究发现,喷涂距离是影响复合粉反应程度及涂层组织结构的主要因素,枪距在100mm时,反应最充分,涂层组织最致密．     

Cr3C2对等离子钴基堆焊层组织及性能的影响

采用等离子堆焊技术在低碳钢表面制备钴基合金堆焊层(Co40)及添加质量分数20%和40%Cr3C2的钴基合金复合堆焊层(Co40+20%Cr3C2,Co40+40%Cr3C2)。利用光学显微镜、扫描电镜、X射线衍射仪以及磨损实验机等研究不同添加量的Cr3C2对钴基合金堆焊层组织和耐磨性能的影响。结果表明:Co40堆焊层由γ-Co和Cr23C6组成;添加Cr3C2粉末后,堆焊层出现未熔的Cr3C2和Cr7C3及Cr23C6相,且明显改变了其组织特征,Co40+20%Cr3C2堆焊层仍以亚共晶方式结晶,但其组织得到明显的细化和均匀化,而Co40+40%Cr3C2堆焊层转变为过共晶方式结晶,其组织由大量初生碳化物和枝晶组织组成;Co40+Cr3C2复合堆焊层的硬度和耐磨性较Co40堆焊层均得到显著提高,且随着Cr3C2添加量的增加而相应提高。     

熔覆速度对氩弧熔覆铁基合金涂层组织及性能的影响

在低碳钢表面熔覆一层耐磨材料,用以取代昂贵的整体合金,既可保留低碳钢高塑及韧性的特点,又能大幅提高表面层的硬度和耐磨性,从而达到降本增效的目的．利用氩弧熔覆技术,在廉价的Q235钢材表面制备了铁基合金涂层,并测试了涂层的硬度和耐磨性;研究了熔覆速度对涂层合金的组织、硬度和耐磨性的影响．试验结果表明,采用氩弧熔覆工艺可以在Q235钢基表面上获得与基体结合良好、组织细密且具有较高硬度和耐蚀性的铁基合金熔覆层;适当提高熔覆速度,可使熔覆层组织获得有效的细化,且增大涂层合金的硬度,提高了耐磨性．     

Oxidation performance of Fe-Al/WC composite coatings produced by high velocity arc spraying

Fe-Al intermetallics with remarkable high-temperature intensity and excellent erosion, high-temperature oxidation and sulfuration resistance are potential low cost high-temperature structural materials. But the room tem perature brittleness induces shape difficult and limits its industrial application. The Fe-Al intermetallic coatings were prepared by high velocity arc spraying technology with cored wire on 20G steel, which will not only obviate the problems faced in fabrication of these alloys into useful shapes, but also allow the effective use of their outstanding high-temperature performance. The Fe-Al/WC intermetallic composite coatings were prepared by high velocity arc spraying technology on 20G steel and the oxidation performance of Fe-Al/WC composite coatings was studied by means of thermogrativmetic analyzer at 450, 650 and 800 ℃. The results demonstrate that the kinetics curve of oxidation at three temperatures approximately follows the logarithmic law. The composition of the oxidized coating is mainly composed of Al2 O3, Fe2 O3, Fe3 O4 and FeO. These phases distribute unevenly. The protective Al2 O3 film firstly forms and preserves the coatings from further oxidation.     

PTA clad （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating

A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness, and dry-sliding wear resistance of the coating were evaluated. The results indicate that the microstructure of the coating, which was composed of （Cr, Fe）7C3 primary phase uniformly distributed in the γ-Fe, and the （Cr, Fe）7C3 eutectic matrix was metallurgically bonded to the 0.45wt%C carbon steel substrate. From substrate to coating, the microstructure of the coating exhibited an evident epitaxial growth character. The coating, indehiscent and tack-free, had high hardness and appropriate gradient. It had excellent wear resistance under the dry sliding wear test condition.     

Effect of Various Additives on Performance of Plasma Electrolytic Oxidation Coatings Formed on AZ31 Magnesium Alloy in the Phosphate Electrolytes

Plasma electrolytic oxidation(PEO) coatings were prepared on AZ31 magnesium alloy using alkaline phosphate as base electrolyte system, and with the addition of sodium silicate(Na_2SiO_3), sodium aluminate(NaAlO_2) and potassium fluorozirconate(K_2ZrF_6) as additives. The microstructure, phase composition and element composition as well as surface profile of the PEO coatings were analyzed by means of scanning electron microscopy(SEM), X-ray diffraction(XRD), energy dispersive X-ray spectroscopy(EDS), and threedimensional(3 D) optical profilometry. The corrosion and wear properties were evaluated by electrochemical potentiodynamic polarization in 3.5 wt% Na Cl solution and ball-on-disc wear tests, respectively. The results showed that the anions of the additives effectively participated in the coating formation influencing its microstructural features, chemical composition, corrosion resistance and tribological behaviour. It was observed that the sample treated by PEO in the electrolyte solution containing K_2ZrF_6 as an additive showed better corrosion and abrasive resistance.     

激光熔覆原位自生TiC-VC复合增强铁基合金层的研究

利用钛铁、钒铁、石墨等组分,采用5kW横流CO₂激光器在低碳钢板上熔覆制备出原位自生TiC-VC复合碳化物颗粒增强Fe基合金层.利用金相显微镜、X射线衍射仪、电子探针及滑动磨损试验机,研究了合金熔覆层的显微组织及性能.研究结果表明,通过钛铁、钒铁与石墨之间的反应,可以得到TiC-VC复合碳化物增强相,细小的TiC-VC复合碳化物颗粒弥散分布在Fe基体之中,合金熔覆层的耐磨性在一定范围内随增强颗粒的增加而提高.     

Microstructure and Wear Behaviour of Laser-Induced Thermite Reaction Al2O3 Ceramic Coatings on Pure Aluminum and AA7075 Aluminum Alloy

Wear-resistant laser-induced thermite reaction Al_2O_3 ceramic coatings can be fabricated on pure Al and AA7075 aluminum alloy by laser cladding(one-step method)and laser cladding followed by laser re-melting(two-step method)using mixed powders CuO-Al-SiO_2 in order to improve the wear properties of aluminum and aluminum alloy,respectively.The microstructure of the coatings was characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD).The wear resistance of the coatings was evaluated under dry sliding wear test condition at room temperature.Owing to the presence of hardα-Al_2O_3 andγ-Al_2O_3 phases,the coatings exhibited excellent wear resistance.In addition,the wear resistance of the coatings fabricated by two-step method is superior to that of the coatings fabricated by one-step method.     

MIG熔化注射WC增强耐磨层的显微组织分析和耐磨性研究

采用MIG熔化注射方法在低碳钢基体上制备WC颗粒增强耐磨层,利用扫描电镜对耐磨层进行组织分析,并测试耐磨层的硬度和耐磨性能。结果表明,耐磨层成形良好,WC颗粒在耐磨层中分布较均匀,无沉底现象,和胎体金属结合良好,最外层有少量熔化分解。紧邻WC颗粒析出有Fe3W3C和/或Co3W3C,稍远处为鱼骨状共晶组织。胎体金属为马氏体组织,WC型碳化物沿晶界呈网状析出。多道熔化注射没有明显增大WC熔化分解程度。耐磨层中WC颗粒硬度没有降低,胎体金属硬度为Hv700左右,耐磨层的耐磨性约为基体的850倍.     

镍钛合金表面含壳聚糖的钙磷复合涂层的仿生合成

将高浓度模拟体液5×SBF与壳聚糖溶液相互结合,在预处理后的镍钛合金基体上快速形成了含壳聚糖的钙磷复合涂层。电化学测试表明,钙磷涂层复合壳聚糖以后,阳极极化曲线中的钝化区变宽,击穿电位明显升高,涂层的抗腐蚀性增强。复合涂层在单倍模拟体液SBF中浸泡4d后,SEM、EDS对涂层的测试结果表明,复合涂层具有良好的生物活性。