Influence of oxides on high velocity arc sprayed Fe-Al/Cr_3C_2 composite coatings

1INTRODUCTION Arcspraying(AS)isatechniquethatthemet alisheatedtodropletsbyanelectricarcandthensprayedontosubstratesbythecompressedair. Highvelocityarcspraying(HVAS)technologyisdevelopedonthebasisofAS.Aspecialtubede signedaccordingtotheprincipleofaerodynamicsis mountedattheexitofcompressedair.Theveloci tyanddistributionofmelteddropletsbecomehigh erandmoreuniform,respectively.Asaresult,acoatingwithlowporosity(2%)andhighdensity andbondstrengthcanbeobtained[15].Fe Alin termetalliccompound…     

火焰喷涂镍基碳化钨涂层的高温冲蚀磨损特性

ｘ－射线衍射、能谱分析和ＳＥＭ研究镍基碳化钨自熔性合金粉末火焰喷涂涂层，合金中碳化钨的含量对涂层的组织结构、孔隙率和硬度产生重要影响，进而使涂层的高温冲蚀磨损机制发生相应的变化。随涂层中碳化钨含量的增高，材料流失由基体塑性变形为主转变为碳化钨硬质相的脆性断裂为主，高韧性的Ｎｉ（γ）固溶体对碳化钨起支撑保护作用，弥散分布的硬质相改善了涂层的耐磨性。结果表明，Ｎｉ－ＷＣ３５涂层具有最佳的抗高温冲蚀性能     

Erosion-Corrosion Behaviors of High Velocity Arc Sprayed Fe-Al/Cr3 C2 Coating

1 IntroductionArc Spraying (AS) is a technique that utilizes anelectric arc as the heat source to melt wires into droplets ,which are subsequentlysprayed ontosubstrates bytheflowof compressed air . High Velocity Arc Spraying (HVAS)technology was developed on the basis of AS. Aspecialtube designed according to the principle of aerodynamicswas mounted at the exit of compressed air .Thenthe hightemperature fuel air or compressed air was accelerated bythe tube .Hence ,a higher velocityand be…     

熔融锌对沉没辊腐蚀磨损过程的影响

为了研究材料或涂层在熔融锌中的耐腐蚀磨损情况,自行研制了一种耐熔融锌腐蚀磨损试验机,并介绍了该试验机的工作原理和结构组成.利用该腐蚀磨损试验机,对Al_2O_3涂层在锌液中的腐蚀磨损性能进行了测试,利用扫描电子显微镜与能谱仪对比分析了未经腐蚀磨损试件、腐蚀磨损5 d试件、腐蚀磨损10 d试件的组织和成分变化,并对Al_2O_3涂层的失效机制进行了分析.结果表明,该腐蚀磨损试验机可以模拟热镀锌沉没辊在熔融锌液中的工作状况,从而可以对沉没辊的失效情况进行更直观的分析,因而可为耐熔融锌腐蚀磨损材料或涂层的研究提供理想平台.     

氩弧熔覆镍基自熔合金的工艺研究

采用氩弧熔覆工艺在Q235钢基体上获得了F102Fe镍基合金熔覆层.测试了涂层的硬度和耐腐蚀性，借助光学金相显微镜、扫描电子显微镜观察其显微组织，进而对熔覆工艺、合金组织及熔覆层性能之间的关系进行详细阐述.研究结果表明，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、具有较高硬度和耐蚀性的F102Fe合金熔覆层.在相同的情况下，增加电流强度或减少熔覆层的厚度，组织由共晶向亚共晶转变；随熔覆层的硬度、耐蚀性降低，塑性有所改善.     

Influence of oxides on high velocity arc sprayed Fe-Al／Cr3C2 composite coatings

Fe-Al/Cr3C2 coatings were sprayed on low steel by high velocity arc spraying(HVAS) technology. The influences of oxides on erosion, corrosion and wear behavior for high velocity arc sprayed Fe-Al/Cr3C2 coatings were studied. The results show that HVAS-sprayed Fe-Al/Cr3C2 coatings have good erosion, heat corrosion and wear resistance. The erosion resistance improves with the increase of the temperature. On one hand, the ferrous oxides are incompact, so they peel off the surface of the coatings easily during the high temperature erosion. On the other hand, compact Al2O3 films on the surface can protect the coatings.     

等离子喷涂NiCr/Cr_2C_3、Ni/C及其复合涂层的耐磨性能

为了加强车辆机械零件的表面防护,采用等离子喷涂工艺在304N不锈钢表面分别制备了NiCr/Cr_2C_3涂层、Ni/C涂层以及NiCr/Cr_2C_3和Ni/C复合涂层,观察了涂层组织形貌,测试了涂层硬度和耐磨性,分析了涂层的摩擦磨损机理.结果表明,3种涂层中NiCr/Cr_2C_3和Ni/C复合涂层的耐磨性能最好.金属粘结相NiCr可以起到足够的支撑作用,从而防止涂层剥离与黏着磨损的产生.Ni/C作为固体润滑剂,通过自润滑作用降低了涂层的整体摩擦系数.     

Microstructure and corrosion properties of laser cladding MoNi based alloy coatings

Mo-based alloys are widely used for their excellent wear and corrosion resistance as well as high temperature resistance.Mo-NiCrBSi and Mo-Ni alloy coatings were prepared on 1020 water wall tube by laser cladding technology in the present study.The microstructure and phase compositions were analyzed by means of the scanning electron microscopy(SEM),energy-dispersive spectroscopy(EDS)and X-ray diffractometry(XRD).The corrosion properties of the coatings were evaluated by an electrochemical experiment at room temperature in 3.5 wt.%NaCl electrolyte.With increasing content of Mo,the structure homogeneity in Mo-Ni coatings deteriorated,the grain size increased,the average hardness and the corrosion resistance declined,due to the more content of harmful phases.Compared to the Mo-Ni coatings,the overall performance was better for the Mo-NiCrBSi,which had the higher hardness contributed by the element B and Si as well as the better corrosion resistance due to the addition of Cr.     

Effect of Salt Spray Corrosion on Tribological Properties of HVOF Sprayed NiCr-Cr_3C_2 Coating with Intermediate Layer

The objective of the present work was to determine the influence of the neutral salt spray corrosion on the wear resistance of HVOF sprayed NiCr-Cr_3C_2 coating with intermediate layer. Ni-Zn-Al_2O_3 coatings as interlayers were prepared by low pressure cold spray(LPCS) between NiCr-Cr_3C_2 cermet coatings to form a sandwich structure to enhance the corrosion resistance properties. The tribological properties were examined using the UMT-3 fricition and wear tester by line-contact reciprocating sliding under dry and salt spray one week corrosion. The morphology, element distribution, and phase compositions of the coating and worn sufaces were analyzed by using scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction respectively. The corrosion behavior of the coating was studied by the open-circuit potential, the electrochemical impedance spectroscopy, potentiodynamic polarization, and salt spray corrosion methods. It is found that the sandwich structured coating has better corrosion resistance than the single layer coating. The results show that under dry wear conditions, the wear mechanism is abrasive and adhesive wear, whereas under salt spray corrosion conditions it becomes corrosion wear. The friction coefficient of the sandwich structured coating after salt spray corrosion is slightly lower than the dry friction coefficient, but the weight of the wear loss is lower than that under dry condition.     

Effect of salt spray corrosion on tribological properties of HVOF sprayed NiCr-Cr<Subscript>3</Subscript>C<Subscript>2</Subscript> coating with intermediate layer

The objective of the present work was to determine the influence of the neutral salt spray corrosion on the wear resistance of HVOF sprayed NiCr-Cr₃C₂ coating with intermediate layer. Ni-Zn-Al₂O₃ coatings as interlayers were prepared by low pressure cold spray (LPCS) between NiCr-Cr₃C₂ cermet coatings to form a sandwich structure to enhance the corrosion resistance properties. The tribological properties were examined using the UMT-3 fricition and wear tester by line-contact reciprocating sliding under dry and salt spray one week corrosion. The morphology, element distribution, and phase compositions of the coating and worn sufaces were analyzed by using scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction respectively. The corrosion behavior of the coating was studied by the open-circuit potential, the electrochemical impedance spectroscopy, potentiodynamic polarization, and salt spray corrosion methods. It is found that the sandwich structured coating has better corrosion resistance than the single layer coating. The results show that under dry wear conditions, the wear mechanism is abrasive and adhesive wear, whereas under salt spray corrosion conditions it becomes corrosion wear. The friction coefficient of the sandwich structured coating after salt spray corrosion is slightly lower than the dry friction coefficient, but the weight of the wear loss is lower than that under dry condition.     

超音速火焰喷涂WC-10Co4Cr 涂层组织及耐磨耐蚀性研究

采用超音速火焰喷涂工艺在不同喷涂距离下制备了WC-10Co4Cr涂层,并对其组织结构及耐磨耐腐蚀性能进行了研究。利用金相显微镜、扫描电子显微镜、X射线衍射仪分析了涂层的组织结构和相组成,并测试了涂层显微硬度、孔隙率;对涂层磨损表面进行了观察分析,探讨了涂层的失效形式。结果表明,喷涂距离对涂层的组织结构及耐磨性具有一定影响。适当增加喷涂距离,粒子由于在焰流中停留时间增加而使熔化程度加大,撞击基体后扁平化现象明显。因此,涂层的致密度、耐磨性、耐腐蚀性都有所提高。当喷涂距离为380mm 时,涂层呈现出较好的耐磨性及耐腐蚀性。     

热处理温度对CrMoNi铸铁基化学镀Ni-P层显微结构与性能的影响

采用化学镀技术在CrMoNi高合金铸铁表面沉积Ni—P合金镀层,采用维氏硬度仪、M-2000摩擦磨损机、SEM和EDAX等手段研究了热处理温度对Ni-P合金镀层组织结构和性能的影响,并对磨损机理进行了分析．研究结果表明：CrMoNi合金基体表面沉积Ni—P合金镀层能有效改善CrMoNi合金基体硬度和耐磨性．经过350℃热处理时,获得的Ni-P合金镀层硬度达到极值1072HV,为基体硬度的4．5倍,耐磨性最佳,磨损率仅为基体的0．68％o,镀层的磨损机制为轻微的黏着磨损．     

镁合金表面等离子喷涂纳米陶瓷涂层研究

为了扩大镁及其合金的应用范围，必须有效地提高其表面的硬度、耐磨性、耐腐蚀性和瞬时耐热性。在压铸镁合金的表面用具有纳米尺寸的Al2O3 3％TiO2粉粒进行等离子喷涂，并借助XRD、AFM、SEM等分析方法，对涂层的微观组织进行了观察分析，并对涂层和基体的结合强度及表面硬度进行了测量。     

Plasma preparation method and tribological properties of diamond-like carbon coating on magnesium alloy AZ31 substrate

Magnesium alloys are light weight and exhibit good recyclability but suffer from low hardness and wear resistance.In this study,the hardness and wear resistance of AZ31 magnesium alloy were improved by depositing diamond-like carbon(DLC)films as hard protective coatings using ion-beam-enhanced deposition with various CH_4/H_2 ratio,gas flow rates and accelerating voltages.The supporting effect of the magnesium alloy was enhanced by the production of a graded interfacial layer which is composed of film atoms and substrate atoms.The composition and mechanical properties of the DLC coatings were characterized using scanning electron microscopy(SEM),Raman spectroscopy,Rockwell test and nano-indentor.The tribological properties of the coating were also investigated using a frictional surface microscope with an in situ observation system and friction force measurements.The DLC films were characterized by a lower intensity ratio of the D-peak to G-peak(I_D/I_G),higher hardness,and improved tribological properties when deposited at a lower accelerating voltage(6 kV).At the CH_4/H_2 ratio of 1:99 and 6 sccm/6 kV,minimum I_D/I_G values of 0.62,relatively low friction force value of 0.12 N,and a maximum hardness of 4056HV were attained respectively.In addition,the DLC film exhibited improved wear resistance and a shallower wear track at this condition.     

Effectiveness of Surface Coatings Against Intensified Sewage Corrosion of Concrete

Three different kinds of coatings were coated on the concrete surface, and the changes in appearance, surface roughness, microstructure and components of coatings in artificial sewage were investigated. In addition, the strength, micrograph, mineral compositions and pore structure of concrete specimens after removing coatings were also studied. The results show that epoxy coal tar pitch coating(ECTPC) has the best effect of protecting concrete from the sewage corrosion. After being immersed in sewage for 90 days, the compressive strength of concrete coated with ECTPC is still as high as that of specimen immersed in water, and the cement paste has a high CH content and dense structure with low porosity, which mainly accounts for its excellent barrier property and certain antibacterial function. Cement-based bactericidal coating(CBC) also has good effectiveness to sewage corrosion of concrete. The strength and microstructure of concrete coated with CBC in sewage are still significantly superior to those of uncoated concrete. Although cement-based capillary crystalline waterproofing coating(CCCWC) is a good waterproof material, it is not suitable for the corrosion resistance of concrete in sewage. After 2 months corrosion, almost all of the CH crystals in coating reacted with the metabolic acid substance by microbes. Therefore, the strength and pore structure of concrete coated with CCCWC are only slightly superior to those of uncoated concrete. Overall, the protective effect of cement-based inorganic coatings is relatively poor.     

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。     

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.     

等离子喷涂陶瓷复材的性能和应用及其发展

综述了等离子喷涂陶瓷涂层在克服金属零件失效方面所发挥的重要作用。把发生在材料表面的磨损按实际情况区分为典型的六大类,工件实施等离子喷涂陶瓷涂层后,具体的实验、生产中得来的数据表明等离子喷涂陶瓷涂层后材料表面抗磨损能力均显著提高。由于材料表面采用等离子喷涂抗腐蚀的陶瓷涂层覆盖在金属基体上,从而屏障了外界腐蚀性物质对金属基体的浸蚀,从而提高了材料的抗腐蚀能力。实验数据说明了通过对涂层进行封闭处理或激光重熔,可大大减少涂层中的气孔率,从而提高耐腐蚀性。探讨了适用于高温条件下的陶瓷涂层所应有的良好性能,并分析了三种典型应用于高温环境下的陶瓷涂层。最后,提出了等离子喷涂陶瓷涂层的发展方向及现行阶段所急需解决的问题。     

Mechanical and Tribological Properties of CrN Coated Inconel X750

Three CrN coatings were deposited on the Inconel X750 through the metal vapor vacuum arc ion implantation and the magnetic filtered cathodic vacuum arc deposition system(MEVVA-FCVA) with the N_2 flow rates of 10, 50, and 100 sccm, respectively. The surface morphologies and cross-section morphologies of the CrN coatings were obtained through scanning electron microscopy(SEM) and an optical profilometer.The microstructures of the coatings were characterized through X-ray diffraction(XRD). The hardness and the elastic modulus of the coatings were tested by a nano-hardness tester. The adhesion strength and friction coefficients were investigated through scratch tests and ball-on-disk tests and the wear tracks were tested by the optical profilometer. The experimental results indicate that the CrN coating deposited on the Inconel X750 substrate displays a uniform thickness and a smooth surface. The mechanical properties behaves well as the N_2 flow rate varies. The CrN coating significantly reduces the friction coefficient fluctuation and improves the antiadhesion and anti-wear properties of the Inconel X750.     

Morphology and tribological properties of Ni/n-SiO_2 composite coatings by pulse-reverse current brush-plating

1INTRODUCTION Pulse reversecurrent(RC)platingisanew technologycomingwithpulsecurrent(PC)andre versecurrent.Onthisaspect,earlierstudiesmani festedthat[16],intheconditionofRC,theeffectofelectricdoublelayerwasrestrained,thecontrol ofcrystallinegrowthwasenfor…