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.     

High temperature behaviors of high velocity arc sprayed Fe-Al/Cr3C2 composite coatings

Fe-Al/Cr3C2 composite coatings were manufactured using high velocity arc spraying （HVAS） technology. The high temperature erosion, wear and corrosion resistance of the coatings were investigated. The coating properties such as bonding strength, porosity, hardness as well as microstructures were characterized. The results show that the coatings have relatively high heat tremble bond strength, hardness, and typical layer-shaped coatings＇ microstructures. With the rise of temperature, the coating erosion resistance increases too; the impingement angel does effects on erosion properties, and the erosion mechanism changes from ductile to brittle behaviors at 450℃. The coatings have good room temperature wear resistance and relatively good high temperature resistance. The wear mechanism of the coatings is peeling wear behavior. The coatings have excellent high temperature corrosion resistance because of the produce of oxides during corrosion.     

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.     

锅炉受热面NiCr涂层抗高温热腐蚀机制与性能的研究

针对电站锅炉受热面高温腐蚀的影响,通过采用电弧喷涂工艺,研究了Q235钢板表面电弧喷涂PS45、FeCrAl、4Cr13合金涂层后在高温条件下的热腐蚀机制与性能.热腐蚀动力学试验和分析结果显示,在700℃下腐蚀77 h、Na2SO4+K2SO4盐膜量为3~4 mg/cm2的试验条件下,测试得到的PS45、FeCrAl、4Cr13合金涂层的热腐蚀速度分别为υ=0.38t-0.59、υ=1.35t-0.12和υ=1.79t-0.23.涂层表面的成分和组织分析结果表明,Q235钢板表面的PS45涂层之所以表现出比FeCrAl、4Cr13涂层更高的抗热腐蚀(Na2SO4/K2SO4)性能,其原因在于PS45镍基合金中含有最多的Cr,涂层表面的Cr2O3膜层具有较高的连续性、致密性和稳定性.     

锅炉受热面NiCr涂层抗高温热腐蚀机制与性能的研究

针对电站锅炉受热面高温腐蚀的影响,通过采用电弧喷涂工艺,研究了Q235钢板表面电弧喷涂PS45、FeCrAl、4Cr13合金涂层后在高温条件下的热腐蚀机制与性能.热腐蚀动力学试验和分析结果显示,在700℃下腐蚀77 h、Na2SO4＋K2SO4盐膜量为3-4 mg/cm2的试验条件下,测试得到的PS45、FeCrAl、4Cr13合金涂层的热腐蚀速度分别为υ=0.38t-0.59、υ=1.35t-0.12和υ=1.79t-0.23.涂层表面的成分和组织分析结果表明,Q235钢板表面的PS45涂层之所以表现出比FeCrAl、4Cr13涂层更高的抗热腐蚀（Na2SO4/K2SO4）性能,其原因在于PS45镍基合金中含有最多的Cr,涂层表面的Cr2O3膜层具有较高的连续性、致密性和稳定性.     

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.     

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 temperature 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°C. 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 Al₂O₃, Fe₂O₃, Fe₃O₄ and FeO. These phases distribute unevenly. The protective Al₂O₃ film firstly forms and preserves the coatings from further oxidation. Foundation item: Project(50235030) supported by the National Natural Science Foundation of China; Project(98BK014) supported by the Foundation of State Economy Trade Committee of China     

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…     

热喷涂FeCrAl/Al复合涂层抗高温硫化的研究

为了提高材料的抗热腐蚀性能,采用电弧喷涂方法在钢铁基体表面施加FeCrAl/Al复合涂层,通过沉积Na2SO4的900℃热腐蚀试验以及二硫化碳生产装置中的现场挂片试验,研究了FeCrAl/Al复合涂层的高温硫化表现。实验结果表明:FeCrAl/Al复合涂层提高了钢铁材料的抗高温硫化腐蚀能力,在高温硫化初期,外表面的Al涂层首先发生氧化,形成连续的Al2O3层,显著地减缓了硫原子向复合涂层内部的扩散速度。随着复合涂层中Cr、Al等有效抗硫化合金元素的相互扩散,形成FeCr金属间化合物层,进一步阻碍硫原子扩散,对钢铁基体材料提供有效的高温硫化防护作用。     

钛合金微弧氧化抗高温氧化研究现状

钛合金因具备高强度、耐蚀性及比强度高等特点被广泛应用于军用及民用等各个领域。但是,其在高温环境使用时会发生高温氧化反应,导致其性能降低,限制了它的使用。微弧氧化（MAO）技术可使钛合金表面原位生长一层致密的氧化膜,膜层与金属基体结合能力强,拥有一定的耐磨、耐蚀及抗高温等特性,且其工艺流程简单高效、成本低而环保,可明显提高钛合金的抗氧化性,延长其在高温条件下的服役时间。综述了MAO技术在钛合金抗高温氧化领域的研究现状,总结了反应参数、电解液、微弧氧化反应时间及电源模式等条件对微弧氧化陶瓷膜层结构和抗高温氧化性能的影响。     

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.     

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.     

等离子喷涂复合陶瓷涂层及其耐磨性能

用等离子喷涂技术制取了ＭＯ＋Ａｌ２Ｏ３－ＴｉＯ２、ＭＯＳ２＋Ａｌ２Ｏ３、ＴｉＯ２＋Ｃｒ３Ｃ２ＮｉＣｒ和ＭｏＳ２＋Ｃｒ３Ｃ２－ＮｉＣｒ复合涂层．利用ＳＥＭ、ＸＲＤ、和ＸＰＳ等技术．观察和分析了涂层的显微结构和喷涂过程中的物相变化及添加成分对涂层耐磨性能的影响．在ＭＭ－２００型磨损试验机上测定了涂层的滑动摩擦系数和磨损率．结果表明；Ｍｏ、ＭｏＳ２与Ａｌ２Ｏ３－ＴｉＯ２的结合性能较好，ＴｉＯ２、ＭｏＳ２在Ｃｒ３Ｃ２－ＮｉＣｒ涂层的气孔和裂纹处偏聚；添加ＭｏＳ２对Ａｌ２Ｏ３－ＴｉＯ２涂层的物相组成有明显的影响；适量的ＭＯ、ＭＯＳ２加入Ａｌ２Ｏ３－ＴｉＯ２中，可以降低涂层的摩擦系数和磨损率；而ＴｉＯ２、ＭｏＳ２加入Ｃｒ３Ｃ２－ＮｉＣｒ中，对涂层的摩擦磨损性能影响不大     

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。     

电弧喷涂铁基涂层的组织与减摩机制分析

为了研究电弧喷涂铁基涂层的组织及减摩机制,采用电弧喷涂技术制备了08Mn2Si、4Cr13和65M n铁基涂层.利用光学显微镜和扫描电子显微镜分析了涂层的组织特征.结果表明,涂层中孔隙的分布是互不连通的,并随机分布.利用Image J计算涂层的孔隙率和氧化物占比,并结合摩擦磨损试验分析了涂层的减摩机制.基于摩擦学理论与摩擦磨损试验,分析了涂层的孔隙储油和氧化物自润滑作用.孔隙和氧化物的存在可以增加涂层的耐磨性,并提高其减摩作用.     

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。     

多弧离子镀TiN涂层工艺及耐蚀性研究

为提高4Cr13马氏体不锈钢的耐蚀性,对其进行多弧离子镀处理,获得TiN涂层,并用X射线衍射仪、显微硬度计、扫描电子显微镜、电化学测量仪对涂层进行物相分析、表面形貌观察、硬度检测以及电化学腐蚀性能测试.结果表明:随着电流的增大,表面的液滴数目和尺寸增大,涂层厚度增加,薄膜硬度也增大;相结构主要为TiN,有明显的择优取向,且随着弧电流的增强,衍射峰强度略有增加.TiN试样在3.5％的NaCl溶液中耐蚀性与基体相当,在1 mol/L的H2SO4溶液中的耐蚀性比基体提高了800倍.     

等离子弧喷焊Mo/Ni60合金复合涂层的研究

采用等离子弧喷焊法制备了Mo/Ni60复合涂层.测定了喷焊层的耐磨性,并用光学显微镜对覆层进行了金相组织观察,利用X射线衍射分析了覆层的相结构.结果表明:加入Mo的镍基等离子喷焊层组织得到均匀化,共晶体细化,耐滑动磨损性能得到改善.     

The Hot Corrosion Performance of NiCr-Cr_3C_2 Cermet Coating to Boiler Tube

1　IntroductionInboilers ,waterwalltubes ,superheatertubes ,economizertubesandreheatertubesareexposedtoverysevereenvironment ,andthehightemperatureoxidation ,hotcorrosion ,abrasiveanderosiveweararerecognizedasthemainfactorscausingthehighwastageofboilertubes .Theovertemperatureofboilertubeswouldacceleratetheiroxidationandcorrosionandfinallyleadthetubestobebroken .Therearevariousmethodstoreducetubewast age ,including :reducinggasvelocities ,changingfuel,installingtubeshields ,changingtubemateria…     

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.