大气等离子喷涂制备Fe基非晶涂层及微观结构表征

选用Fe-10W-4Cr-3Ni-2Mo-4B-4Si-1C(质量比)合金粉末作为喷涂原料,采用大气等离子喷涂工艺在1Cr18Ni9Ti不锈钢基底上制备了Fe基涂层。利用扫描电镜、透射电镜和X射线衍射仪表征了粉末和涂层的相组成和微观形貌;用Olycia m3分析软件对涂层的孔隙率进行测定;用热分析系统对喷涂粉末和涂层从室温到1 173K范围的DSC曲线进行记录;同时,测定了涂层的显微硬度和结合强度。结果表明:大气等离子喷涂制备的Fe基涂层与基底的结合良好,涂层较为致密并且存在灰色氧化带组织,表现出典型的层状组织结构;涂层不但具有低的表面粗糙度和孔隙率,而且具有高的显微硬度和结合强度;所制备涂层中的非晶含量约为89.2%(质量分数),涂层中形成的晶相组织为纳米晶结构。     

不同工艺制备的Ni-Cr-Al-Y合金涂层及性能

采用低压等离子喷涂（LPPS）、常规超音速火焰喷涂（HVOF）和低温超音速火焰喷涂（LT-HVOF）三种工艺在铸造镍基高温合金K438基体上制备了Ni-Cr-Al-Y涂层,并对三种工艺制备涂层的显微结构、元素分布、相组成和基本性能进行对比研究。结果表明：LPPS涂层致密无层状结构,含氧量微小,具有较高的显微硬度和好的抗氧化性;HVOF涂层为典型的层状结构,含氧量高,显微硬度低,抗氧化性差;LT-HVOF涂层含氧量大大降低,具有优良的抗氧化性;三种涂层都发生了元素扩散。     

超音速火焰喷涂钴基陶瓷涂层的组织与性能研究

本文在氧气流量和喷涂距离一定的条件下,研究了燃气流量对超音速火焰喷涂WC-Co涂层显微组织、相结构及性能的影响。结果表明:燃气流量低的涂层结合强度、显微硬度最低,孔隙率最大;燃气流量适中的涂层结合强度最高,显微硬度低于另外两种涂层,燃气流量最高的涂层,燃气流量高的涂层的显微硬度最大。     

超音速火焰喷涂WC/Co涂层的组织性能研究

分析比较了等离子喷涂、超音速火焰喷涂的WC／Co涂层的形貌、显微组织、孔隙率、硬度、结合强度及其耐磨性。结果表明：超音速火焰喷涂涂层具有与粉末相近的相结构，与等离子喷涂相比涂层具有高的致密度、硬度和良好的耐磨性，涂层与基体结合情况也得到很大的改善。     

超音速等离子喷涂超细WC-12Co涂层的性能

采用超音速等离子喷涂系统,分别制备了超细WC-12Co涂层和普通WC-12Co涂层.研究了喷涂粒子在射流中的特性,分析了涂层形貌、成分和相组成,并对两涂层的常规性能(结合强度、显微硬度、孔隙率和耐冲蚀性能)进行了表征.结果表明,超细WC-12Co喷涂粒子在束流中速度更快(500 m/s),两涂层中WC相的氧化、失碳和分解程度比普通等离子喷涂时低.相比之下,超细WC-12Co涂层显微硬度(1350 HV0.3)和结合强度(65 MPa)更高,孔隙率(0.6%)更低,耐冲蚀磨损性能相当.     

等离子喷涂WC-Ni涂层的组织结构及力学性能

采用等离子喷涂技术在不同的喷涂工艺条件下制备WC-Ni涂层。采用X射线衍射(XRD)和扫描电镜(SEM)表征和观察涂层的相结构和显微组织,同时运用压痕法对涂层的显微硬度、弹性模量和断裂韧性进行测试。结果表明,等离子喷涂工艺参数对涂层的组织结构和相结构有显著影响,等离子喷涂功率增加,粒子的熔化程度增加,适当的喷涂距离下沉积形成的涂层致密;等离子功率增加,喷涂过程中会产生WC粒子的失碳,相对于W_2C相,WC_(1-x)相的增加可以同时提高涂层的显微硬度和断裂韧性;与涂层的相组成相比,致密的组织结构对涂层显微硬度、弹性模量和断裂韧性的综合性能的提高更显著。     

电热爆炸定向喷涂法制备钼涂层

运用电热爆炸定向喷涂新方法在45#钢基体上制备了钼涂层。借助扫描电镜以及能谱仪对涂层的组织结构、形貌以及涂层成分进行了分析。借助显微硬度测试仪对涂层硬度进行了测试。利用图像分析软件对涂层的晶粒尺寸进行了测量。实验表明：涂层组织晶粒细小，涂层硬度提高，HV值最大到达14110MPa，为原始硬度的3倍，且涂层致密，孔隙率低。能谱分析表明，喷涂过程没有发生氧化现象。     

超音速火焰喷涂Co-Cr-WC涂层的组织与性能

采用超音速火焰喷涂工艺在Q235B基体上制备Co-Cr-WC涂层;利用金相显微镜、扫描电子显微镜、X射线衍射仪分析涂层的组织结构和相组成,并测试在不同参数下涂层显微硬度、孔隙率和密度.试验结果表明,涂层组织致密,界面结合良好;涂层表面有少量孔隙存在,孔隙率小于1％;显微硬度在HV1 200以上;涂层密度在12.9 g/...     

高速火焰与等离子喷涂WC／Co涂层的性能比较

分析比较了超音速喷涂与等离子体喷涂的ＷＣ／Ｃｏ涂层的形貌,显微组织结构,孔隙率,硬度及其耐磨性,结果表明超音速火焰喷涂的ＷＣ／Ｃｏ涂层具有与粉末相近的相结构,也说ＷＣ颗粒在超音速火焰喷涂过程中,只有极少部分被分解和氧化,同时涂层具有很高的致密度,硬度和良好的耐磨性,涂层与基体的结合情况也得到很大的改善。     

反应火焰喷涂梯度陶瓷涂层的组织与性能

以Ti-B4C-C系团聚粉和Ni-Al"自粘结"复合粉作为喷涂体系,利用反应火焰喷涂技术在金属表面制备了Ti(C,N)-TiB2和NixAly梯度过渡复相涂层,分析了涂层的组织结构,研究了其孔隙率、显微硬度等性能.结果表明,梯度过渡涂层由Ti(C0.7,N0.3)、TiC、TiB2、TiN、Ni3Al、NiAl、Ti、TiO2等多相组成,涂层组织结构具有沿厚度方向的梯度过渡特征,沿远离基体方向,陶瓷相逐渐增多而金属相逐渐减少.引入梯度过渡设计的涂层与基体结合强度提高1倍,孔隙率下降,而涂层的显微硬度也具有沿厚度方向的梯度过渡特征.     

Characterization of plasma sprayed Fe-17Cr-38Mo-4C amorphous coatings crystallizing at extremely high temperature

A Fe-17Cr-38Mo-4C alloy powder was plasma sprayed by three processes: an 80 kW low-pressure plasma spray (LPPS), a 250 kW high-energy plasma spray (HPS), and a 40 kW conventional plasma spray (APS). The as-sprayed coating obtained by the LPPS process is composed of only amorphous phase. As-sprayed coatings obtained by the HPS and APS processes are a mixture of amorphous and crystalline phases. The three as-sprayed coatings exhibit a high hardness of 1000 to 1100 DPN. The amorphous phase in these coatings crystallizes at a high temperature of about 920 K. A very fine structure composed of hard ϰ-phase and carbides is formed after crystallization. The hardness of the coating obtained by LPPS reaches a maximum of 1450 DPN just after crystallization on tempering and retains a high hardness more than 1300 DPN after tempering at high temperatures of 1173 or 1273 K. The corrosion potential of the amorphous coating is the highest among the three coatings and higher than that of a SUS316L stainless steel coating. The anodic polarization measurements infer that the corrosion resistance of the amorphous coating is superior or comparable to SUS316L stainless steel coating in H₂SO₄ solution.     

氧乙炔火焰喷焊镍基复合涂层的显微组织和腐蚀性能研究

目的 研究Ni60和Ni60WC喷焊涂层的显微组织、防腐和耐磨性能及其腐蚀机理,为恶劣工况下服役的零件选择合适的喷焊涂层提供参考.方法 采用氧乙炔火焰喷焊工艺在16Mn钢基体上制备Ni60和Ni60WC涂层,用X射线衍射仪、金相显微镜和扫描电子显微镜分析了喷焊涂层的相结构和显微组织,并采用电化学工作站、盐雾腐蚀试验机、磨粒磨损试验机测试了两种喷焊涂层的防腐和耐磨性能.结果 喷焊层与基体间都存在冶金结合层和热影响区,Ni60涂层的显微组织为NiCr固溶体基体上弥散分布着大量细小粒状和杆状碳化物和硼化物.Ni60WC喷焊涂层组织中,除了具有与Ni60涂层类似的基体相和细颗粒硬质相外,还较均匀地分布着不同尺寸的WC颗粒.Ni60和Ni60WC涂层的磨损率分别为16Mn钢的8.3％和2.3％,自腐蚀电流密度分别为16Mn钢的1.0％和7.6％.另外,基体相和硬质相之间的电偶腐蚀是两种镍基喷焊涂层的主要腐蚀机理.结论 这两种镍基喷焊涂层均能显著提高16Mn钢的抗磨和防腐性能,其中,Ni60喷焊涂层耐腐蚀性更好,Ni60WC喷焊涂层耐磨损性能更好.     

火焰喷涂和等离子喷涂FeCrBSi涂层及其防滑和耐磨性能研究

目的采用大气等离子喷涂(APS)和火焰喷涂(FS)在304不锈钢基体上制备FeCrBSi涂层,并对比研究两种工艺制备涂层的防滑和耐磨性能。方法通过光学显微镜、场发射扫描电镜和X射线衍射仪对涂层的显微形貌和结构进行分析,通过维氏硬度计测试涂层的显微硬度。采用摩擦磨损试验机和三维光学显微镜,测量涂层在干摩擦条件下的摩擦系数和磨损量。结果两种喷涂方法制备的涂层多孔,在喷涂过程中极少发生氧化。与火焰喷涂涂层(749HV0.1)相比,大气等离子喷涂涂层(837HV0.1)具有更高的维氏硬度值。在摩擦试验中,火焰喷涂涂层的磨损率为(38.63±2.37)×10~(-6)m~3/(N·m),而大气等离子喷涂涂层的磨损率为(9.5±0.49)×10~(-6)m~3/(N·m),但两种涂层的摩擦系数区别较小,在频率2 Hz、载荷10 N的条件下的摩擦系数为0.6~0.7。结论两种涂层的磨损机制均为疲劳磨损,喷涂态FeCrBSi涂层具有较好的防滑耐磨性能,且大气等离子喷涂涂层性能优于火焰喷涂涂层。     

Correlation of crystallization behavior and mechanical properties of thermal sprayed PEEK coating

An amorphous PEEK coating was prepared on an Al substrate by a flame spraying process. The amorphous coating was subjected to an annealing treatment under an annealing temperature from 180 to 300 °C and a holding time from 1 to 30 min. The cold crystallization behavior of the as-sprayed coating differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) measurements. The hardness and tribological behavior of the coatings were investigated. Both DSC and WAXD analysis revealed that the annealed coatings exhibited a semi-crystalline structure. Coexistence of double crystal entities in annealed coatings was deduced. The annealed coatings exhibit higher hardness, lower friction coefficient and wear rate. Both the annealing temperature and holding time can benefit the coating hardness. The annealing condition in the studied range has little influence on the tribological behavior of the coatings. The variances of the coating mechanical properties were correlated with the modifications of the coating structures induced by the annealing treatments.     

The tribological behaviour of detonation sprayed TiMo(CN) based cermet coatings

The objective of the present study was to evaluate the tribological performance of 200 μm thick TiMo(CN)–28Co and TiMo(CN)–36NiCo coatings obtained using the detonation spray coating system. Towards the above purpose, the detonation spray coating conditions were optimized to obtain the best coating properties (low porosity, high wear resistance) by varying two of the important coating process variables, i.e., oxygen to fuel ratio and gas volume. In both the coatings it was observed that the best tribological performance and also the lowest porosity were obtained at intermediate OF ratios. However, the coatings with the highest hardness did not exhibit the best tribological performance. A comparison of the tribological performance of the optimized TiMo(CN) type coatings with that of optimized WC–Co coatings revealed that the abrasion resistance of TiMo(CN) type coatings is comparable to that of WC–Co coatings. However, the erosion and sliding wear resistance of TiMo(CN) type coatings were considerably lower than that of WC–Co coatings.     

Influence of HVOF parameters on the corrosion and wear resistance of WC-Co coatings sprayed on AA7050 T7

Thermal spray WC-based coatings are widely used in the aircraft industry mainly for their resistance to wear, reworking and rebuilding operations and repair of worn components on landing gear, hydraulic cylinders, actuators, propeller hub assemblies, gas turbine engines, and so on. The aircraft industry is also trying to use thermal spray technology to replace electroplating coatings such as hard chromium. In the present work, WC-Co coatings were built up on an AA 7050 aluminum alloy using high velocity oxygen fuel (HVOF) technology and a liquid nitrogen cooling prototype system. The influence of the spray parameters (standard conditions, W19S, increasing the oxygen flux, W19H, and also increasing the carrier gas flux, W19F) on corrosion, friction, and abrasive wear resistance were also studied. The coatings were characterized using optical (OM) and scanning electron (SEM) microscopy, and X-ray diffraction (XRD). The friction and abrasive wear resistance of the coatings were studied using Rubber Wheel and Ball on Disk tests. The electrochemical studies were conducted using open-circuit potential (E_OC) measurements and electrochemical impedance spectroscopy (EIS). Differences among coated samples were mainly related to the variation of the thermal spray parameters used during the spray process. No significant differences were observed in the wear resistance for the coatings studied, and all of them showed a wear rate around 10 times lower than that of the aluminum alloy. The results of mass loss and wear rate were interpreted considering different mechanisms. Comparing the different spray parameters, the oxygen flux (higher flame temperature) produced the sample which showed the highest corrosion resistance in aerated and unstirred 3.5% NaCl solution. Aluminum ions were detected on the surface almost immediately after the immersion of samples W19S and W19F in chloride solution, showing that the electrolyte reached the substrate and galvanic corrosion probably occurred. For sample W19H, aluminum ions were not detected even after 120 min of immersion in NaCl solution.     

Characterization of the corrosion performances of as-cast Mg–Al and Mg–Zn magnesium alloys with microarc oxidation coatings

In the present study, corrosion-protective microarc oxidation (MAO) coatings were prepared on AZ31B, AZ80, and ZK60 cast magnesium alloy substrates in an alkaline silicate electrolyte. The corrosion performances of the uncoated and MAO-coated alloys were investigated using electrochemical and salt spray chamber corrosion tests. The microstructure characterization and experimental results show that among the three alloys studied, the ZK60 Mg alloy exhibited the best and AZ31B the least corrosion resistance under the salt spray conditions. The MAO coating provided robust corrosion protection of the Mg substrates and resulted in a significant decrease in the corrosion rate of the alloys by 3–4 orders of magnitude. The MAO coating on ZK60 alloy showed better corrosion protectiveness than that on the AZ series alloys due to the incorporation of different alloying elements in the coating, especially the Zn and Al elements, which are from the Mg substrate. The corrosion performances and mechanisms of the uncoated and MAO-coated Mg alloys are interpreted in terms of the microstructure and phase/chemical compositions of both the substrates and coatings.     

Improving corrosion properties of high-velocity oxy-fuel sprayed inconel 625 by using a high-power continuous wave neodymium-doped yttrium aluminum garnet laser

Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. Despite the use of the latest developments of thermal spraying, such as high-velocity oxy-fuel (HVOF) and plasma spraying, these coatings may in certain service conditions show inadequate performance,e.g., due to insufficient bond strength and/or mechanical properties and corrosion resistance inferior to those of corresponding bulk materials. The main cause for a low bond strength in thermalsprayed coatings is the low process temperature, which results only in mechanical bonding. Mechanical and corrosion properties typically inferior to wrought materials are caused by the chemical and structural inhomogeneity of the thermal-sprayed coating material. To overcome the drawbacks of sprayed structures and to markedly improve the coating properties, laser remelting of sprayed coatings was studied in the present work. The coating material was nickel-based superalloy Inconel 625, which contains chromium and molybdenum as the main alloying agents. The coating was prepared by HVOF spraying onto mild steel substrates. High-power continuous wave Nd:YAG laser equipped with large beam optics was used to remelt the HVOF sprayed coating using different levels of power and scanning speed. The coatings as-sprayed and after laser remelting were characterized by optical microscopy and scanning electron microscopy (SEM). Laser remelting resulted in homogenization of the sprayed structure. This strongly improved the performance of the laser-remelted coatings in adhesion, wet corrosion, and high-temperature oxidation testing. The properties of the laser-remelted coatings were compared directly with the properties of as-sprayed HVOF coatings and with plasma-transferred arc (PTA) overlay coatings and wrought Inconel 625 alloy.     

Microstructure and properties of Al2O3-13%TiO2 coatings sprayed using nanostructured powders

The microstructure and wear performance of M203-13% TiO2 coatings prepared by plasma spraying of agglom- erated nanoparticle powders were investigated. SEM analysis showed that the as-sprayed Al2O3-TiO2 coatings comprise of two kinds of typical region： fully melted region and unmelted/partially melted nanostructured region, which is different than the conventional coating with lamellar structure. It is shown that the microhardness of the nanostructured coatings was about 15%-30% higher than that of the conventional coating and the wear resistance is significantly improved, especially under a high wear load. The nanostructured coating sprayed at a lower power shows a lower wear resistance than the coatings produced at a higher power, because of the presence of pores and microstructural defects which are detrimental to the fracture toughness of the coatings.     

Preparation and characterization of LPPS NiCoCrAlYTa coatings for gas turbine engine

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