等离子喷涂钼基非晶-纳米晶复合涂层的组织与性能

一种多元素钼基非晶-纳米晶合金粉末(含C、Si、B、Cr、Fe、Ni、Mo等)作为喷涂材料,用大气等离子喷涂在316L不锈钢基体上制备涂层,用X射线衍射仪、扫描电镜、透射电镜、显微硬度仪分析测量涂层的组织和性能,并用谢乐公式计算晶粒尺寸。结果表明：所制备的涂层均匀致密,涂层含有非晶和纳米晶,颗粒尺寸为10～50nm;这种非晶纳米晶复合涂层的硬度和弹性模量分别高达1055HV和214．40GPa。     

纳米晶NiSi2/Ti5Si3复合涂层耐磨耐蚀性能研究

采用双阴极等离子溅射技术在TC4合金表面制备了纳米晶NiSi2/Ti5Si3复合涂层。利用XRD、SEM和TEM研究了复合涂层的微观组织特征,利用纳米压入和声发射划痕仪考察了复合涂层的硬度、弹性模量以及涂层与基体的结合力。结果表明：纳米晶NiSi2/Ti5Si3复合涂层由外层厚度为7 μm的NiSi2沉积层和其下3 μm厚的Ti5Si3扩散层组成,沉积层的平均晶粒尺寸约为40 nm,而扩散层的平均晶粒尺寸约为70 nm,且存在大量的栅栏状孪晶。纳米晶NiSi2/Ti5Si3复合涂层硬度呈梯度分布,与基体具有较高的结合强度,其结合力为49 N。纳米晶NiSi2/Ti5Si3复合涂层的比磨损率较TC4合金降低一个数量级以上,且对载荷和温度不具敏感性。与TC4合金相比,纳米晶NiSi2/Ti5Si3复合涂层的腐蚀电流密度降低了两个数量级,且具有更大的容抗弧值     

高速电弧喷涂铝基非晶纳米晶复合涂层的组织及性能

采用自动化高速电弧喷涂系统,将自行研制的粉芯丝材在AZ91镁合金基体表面制备出2种Al基非晶纳米晶复合涂层。采用扫描电子显微镜（SEM）观察非晶纳米晶复合涂层横截面的微观形貌,利用XRD对非晶纳米晶复合涂层进行结构分析。结果表明,非晶纳米晶复合涂层是由非晶相和晶化相共同组成,涂层致密,孔隙少。Al-Ni-Y-Co涂层的维氏硬度值为3117.6 MPa, Al-Ni-Mm-Fe涂层的维氏硬度值为3407.2 MPa,约为传统Al-RE涂层的4倍左右,为AZ91镁合金基体的5倍左右。电化学试验结果表明,Al-Ni-Y-Co、Al-Ni-Mm-Fe涂层的耐蚀性优于传统Al-RE涂层和AZ91镁合金基体。     

高速电弧喷涂铝基非晶纳米晶复合涂层的组织及性能

采用自动化高速电弧喷涂系统,将自行研制的粉芯丝材在AZ91镁合金基体表面制备出2种Al基非晶纳米晶复合涂层。采用扫描电子显微镜(SEM)观察非晶纳米晶复合涂层横截面的微观形貌,利用XRD对非晶纳米晶复合涂层进行结构分析。结果表明,非晶纳米晶复合涂层是由非晶相和晶化相共同组成,涂层致密,孔隙少。Al-Ni-Y-Co涂层的维氏硬度值为3117.6MPa,Al-Ni-Mm-Fe涂层的维氏硬度值为3407.2MPa,约为传统Al-RE涂层的4倍左右,为AZ91镁合金基体的5倍左右。电化学试验结果表明,Al-Ni-Y-Co、Al-Ni-Mm-Fe涂层的耐蚀性优于传统Al-RE涂层和AZ91镁合金基体。     

气保焊堆焊方法制备的铁基非晶合金涂层

以一种多元素铁基合金粉芯丝材(含Fe,Cr,B,Ti,C,Mo等)作为堆焊材料,用CO2气体保护焊堆焊的方法在基体A3钢上制备涂层。用X-射线衍射仪检测涂层的晶体结构,DSC分析非晶的起始晶化温度;透射电镜观察涂层的微观组织结构,扫描电镜观察涂层的形貌,并利用显微硬度仪和高温摩擦磨损试验机分别测量涂层的显微硬度和耐磨损性能。结果表明:所制备的涂层均匀致密,与基体结合良好;涂层含有非晶并且非晶的起始晶化温度约为524℃;这种非晶涂层具有较高的硬度和很好的耐磨损性能,近表面的最高硬度达825 HV0.3,耐磨性是A3钢的5.9倍.     

等离子体增强磁控溅射制备TiAlVSiCN涂层的抗冲蚀性能

目的 提高不锈钢基体的抗固体颗粒冲蚀性能.方法 在不锈钢基体表面,通过等离子体增强磁控溅射系统(PEMS),采用不同偏压工艺制备TiAlVSiCN纳米复合涂层.通过SEM、HRTEM观察涂层的微观形貌与组织,利用XRD、SAD分析涂层的物相组成与晶体结构,并通过划痕仪、纳米硬度计以及冲蚀试验机探究不同工艺涂层的结合强度、纳米硬度以及抗冲蚀性能差异.结果 采用PEMS制备出一系列不同偏压条件下的TiAlVSiCN涂层,涂层组织致密,呈柱状,主要包括纳米晶Ti(Al,V)(C,N)相和非晶相.偏压显著影响涂层的晶粒尺寸和非晶相分布,高偏压下的涂层主要由20～50 nm的Ti(Al,V)(C,N)纳米晶及其周围弥散分布的非晶相组成,而低偏压下的涂层主要由100 nm的Ti(Al,V)(C,N)纳米晶和连续分布的非晶相组成.高偏压下制备的涂层厚度超过20μm,纳米硬度可达(34.6±14.1)GPa,具有优良的结合强度(>65 N)和抗冲蚀性能,其抗冲蚀性能相比不锈钢基体提高近8倍.结论 通过与偏压参数的匹配控制,PEMS可有效调控纳米复合涂层的组织结构,实现硬度与弹性模量的良好匹配,制备出具有优良抗冲蚀性能、厚度达到20μm以上的TiAlVSiCN纳米晶-非晶复合涂层.     

超音速火焰喷涂Fe基非晶/纳米晶涂层的组织性能特征

采用超音速火焰喷涂设备制备了Fe基非晶／纳米晶涂层，采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、显微硬度计等对涂层的微观形貌、结构特征及显微硬度进行了研究。涂层由变形带状粒子、未熔颗粒及少量孔隙组成，涂层致密。由于该方法的冷却速度高，涂层中形成了非晶，后续涂层的加热使部分非晶转变为纳米晶。涂层的显微硬度平均为1084HV0.2，明显高于基体；靠近涂层的基体表面产生了加工硬化。     

电弧离子镀制备TiBN纳米复合涂层

目的在纯N_2气氛环境下,低温制备TiBN纳米复合涂层,为TiBN涂层工业化生产积累科学数据。方法采用离子源增强阴极电弧离子镀系统,在硬质合金衬底上制备TiBN纳米复合涂层,系统研究了N_2气压对TiBN涂层晶体结构、表面形貌、硬度和耐磨性能的影响。结果 N_2气压对TiBN纳米复合涂层的晶体结构、表面形貌、硬度及摩擦系数的影响明显。随着N_2气压的升高,TiBN涂层中的TiN晶相逐渐增多,TiB_2晶相逐渐减少,为TiN晶粒和TiB_2晶粒镶嵌于非晶BN基体的复合结构。在0.5 Pa气压下,涂层硬度达3150HV。对于对磨材料硬质合金而言,TiBN涂层的摩擦系数为0.4左右。结论离子源增强电弧离子镀技术可以用于TiBN涂层的制备,制备出的TiBN涂层为纳米晶镶嵌于非晶的纳米复合涂层,涂层的显微硬度较高。在TiBN纳米复合涂层的工业化生产中,沉积N_2气压不宜偏高。     

电弧喷涂铁基非晶涂层的结构与性能

用电弧喷涂技术在低碳钢基体上制备一种含非晶和纳米晶的Fe基涂层.采用X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、显微硬度仪分析测量涂层的组织和性能.并用谢乐公式计算晶粒尺寸.结果表明,涂层呈典型的层状组织结构,由变形良好的带状粒子相互搭接堆积而成.涂层结构致密,孔隙率低,氧化物含量较少,涂层含有非晶和纳米晶,晶粒尺寸为10~40 nm,利用X射线衍射强度比较法测量涂层中非晶相的含量为55.3%.涂层具有很高的硬度,其显微硬度最高达到1 260 HV0.1.     

纳米晶NiCrC涂层长时加热的显微组织和硬度变化

目的 探讨纳米晶NiCrC涂层长时高温条件下的显微组织和硬度演变规律。方法 采用超音速火焰（HVAF）喷涂低温球磨纳米晶合金粉末（液氮介质）制备了纳米晶NiCrC涂层，在650 ℃空气环境中对涂层进行总时长200 h的等温热处理。采用扫描电子显微镜、X射线衍射仪、透射电子显微镜、维氏显微硬度计等方法，对涂层样品的显微组织、物相构成、晶粒尺寸和显微硬度进行了测试分析，同时对原料粉末也进行了相同条件下的对比分析。结果 NiCrC涂层显微组织的主要特征为：纳米晶金属相基体中弥散分布着细小的碳化物颗粒。在保温过程中，纳米晶涂层发生了再结晶和晶粒长大，并伴随有合金基体的脱溶及碳化物的析出、相变和后续生长等现象。该涂层显示出优良的高温热稳定性，在650 ℃保温50 h后，晶粒平均尺寸由初始态的41 nm增长至相对稳定值约100 nm。保温后涂层的硬度总体有所提升，由初始的697HV300（15 s）先升高至最大值801HV300（15 s），而后降至相对稳定值729HV300（15 s）左右。纳米晶粉末的组织和硬度变化特点与涂层相似。结论 在650 ℃保温过程中，纳米晶NiCrC涂层中的合金相脱溶和晶粒长大导致涂层金属相基体的软化，但细小碳化物颗粒的析出强化以及由相变（Cr7C3→Cr23C6）引起的体积分数增加，不但补偿了基体的软化，而且使涂层的整体硬度有所提高。     

Microstructure and Performances of Nanocrystalline Zinc-nickel Alloy Coatings

THE STUDY on zinc-nickel alloy coatings isdeveloped rapidly because of their higher corrosionresistance and better mechanical characteristics[1-8].The zinc-nickel coatings provide improved corrosionprotection for steels in relatively aggressiveenvironments.It has been found that the maximumprotective ability can be reached with the nickel contentbetween12%and15%[9].Recently,several newzinc-nickel alloy technologies have been developed[10-15]and further researches for better coating andchara…     

Fabrication and Characterization of Thermal-Sprayed Fe-Based Amorphous/Nanocrystalline Composite Coatings: An Overview

This review focuses on the recent development of iron (Fe)-based amorphous/nanocrystalline composite coatings, which have attracted much attention due to their attractive combination of high hardness/strength, elevated abrasive wear resistance, and enhanced corrosion resistance. Accompanying the advancements in various thermal spray technologies, industrial application fields of Fe-based amorphous/nanocrystalline composite coatings are becoming more diverse. In the main part, the typical empirical rules for the design of amorphous alloys with high glass-forming ability are generalized and discussed at first. Then various thermal spray technologies for the fabrication of Fe-based amorphous/nanocrystalline composite coatings, such as high velocity oxygen/air spray (HVOF/HVAF), air plasma spray (APS), low-pressure plasma spray (LPPS), high-energy plasma spray (HPS), and high velocity arc spray (HVAS) processes, are introduced. The microstructures, hardness, wear resistance, and corrosion resistance of Fe-based amorphous/nanocrystalline composite coatings formed using these thermal spray technologies are reviewed and compared. Finally, the existing challenges and future prospects are proposed.     

A comparative study on the electrochemical behaviour of amorphous and nanocrystalline cobalt–tungsten electrodeposited coatings

Amorphous and nanocrystalline cobalt–tungsten coatings were electrodeposited from a citrate-ammonia bath on copper substrates. Both coatings showed a nodular surface morphology, but a microcrack network was observed in the amorphous coating. The cyclic voltammograms of both deposits revealed anodic and cathodic low-current plateaus around the open circuit potential, exhibiting a passive behaviour. Mott–Schottky analysis showed that the passive films exhibit n-type semiconductivity behaviour and that formed on the amorphous coating showed higher crystal defects. Electrochemical impedance spectroscopy revealed that the amorphous coating has higher corrosion resistance than the nanocrystalline one at both open circuit and anodic potentials. This was attributed to the higher pore resistance of passive film formed at the open circuit potential and more chemical stability of the amorphous coating which reduces its dissolution at the anodic potential. The plugging of the microcrack network in the amorphous coating by corrosion products eliminated the negative effect of microcracks.     

Synthesis and Erosion Behaviors of Nanoscale Coatings Prepared by Wire Arc Spraying

The effects of erosive parameters,such as impact angles and environment temperature,on erosion properties of FeBSiCrMnNb nanoscale coatings were investigated.A series of coatings were prepared by wire arc spraying process.The microstructure of the coating consists of amorphous andα(Fe,Cr)nanocrystalline phase.The nanocrystals with average size of 39 nm are homogenously dispersed in amorphous matrix.The erosion results reveal that the coating exhibits better erosion resistance at lower impact angle.The erosion rates of the coating decrease as function of environment temperature.The relatively erosion resistance of the nanoscale coating is 3.7 times higher than that of AISI1045 steel substrate at 650°C.The main failure mechanism of the coating is brittle fracture.     

Study on corrosion behaviour of nanocrystalline and amorphous Co–P electrodeposits

Abstract

In this study, corrosion properties of nanocrystalline and amorphous Co–P coatings prepared using dc electrodeposition were investigated. The morphology of amorphous coatings was smoother and brighter than nanocrystalline coatings with 'cauliflower' morphology. Tafel polarisation tests of the coatings in 0·1M H₂SO₄ solution revealed that the amorphous coating had better corrosion resistance than the nanocrystalline one. Corrosion resistance of both coatings decreased after annealing. On the nanocrystalline coating, corrosion attacks were localised around the nodules on the surface while a more uniform type of attack was observed on amorphous coatings. Neither nanocrystalline nor amorphous coatings showed passivation in 0·1M H₂SO₄ solution, but both of them showed an active–passive behaviour in 10%NaOH solution due to the formation of Co(OH)₂ as fine hexagonal shape products which acted as a passive layer. The passive current density of the amorphous coating was higher than that of the nanocrystalline one, but it was decreased markedly by annealing. However, annealing had no significant effect on the passivation behaviour of the nanocrystalline coating.     

Structure, morphology and chemical composition of sputter deposited nanostructured Cr-WS2 solid lubricant coatings

WS₂ and Cr-WS₂ nanocomposite coatings were deposited at different Cr contents (approximately 15-50 at.%) on silicon and mild steel substrates using an unbalanced magnetron sputtering system. X-ray diffraction (XRD) was used to study the structure of Cr-WS₂ coatings and the bonding structure of the coatings was studied using X-ray photoelectron spectroscopy (XPS). The characterization of different phases present in Cr-WS₂ coatings was carried out using micro-Raman spectroscopy. The XPS and Raman data indicated the formation of a thin layer of WO₃ on the surface of Cr-WS₂ coatings and the intensity of the oxide phase decreased with an increase in the Cr content, which was also confirmed using energy-dispersive X-ray analysis results. The surface morphologies of WS₂ and Cr-WS₂ coatings were examined using field emission scanning electron microscopy (FESEM) and atomic force microscopy. It has been demonstrated that incorporation of Cr in WS₂ strongly influences the structure and morphology of Cr-WS₂ coatings. The XRD and FESEM results suggested that increase in the Cr content of Cr-WS₂ coatings resulted in a structural transition from a mixture of nanocrystalline and amorphous phases to a complete amorphous phase. The cross-sectional FESEM data of WS₂ coating showed a porous and columnar microstructure. For the Cr-WS₂ coatings, a mixture of columnar and featureless microstructure was observed at low Cr contents (≤ 23 at.%), whereas, a dense and featureless microstructure was observed at high Cr contents. Detailed cross-sectional transmission electron microscopy (TEM) studies of Cr-WS₂ coatings prepared at Cr content ≤ 23 at.% indicated the presence of both nanocrystalline (near the interface) and amorphous phases (near the surface). Furthermore, high-resolution TEM data obtained from the nanocrystalline region showed inclusion of traces of amorphous phase in the nanocrystalline WS₂ phase. Potentiodynamic polarization measurements indicated that the corrosion resistance of Cr-WS₂ coatings was superior to that of the uncoated mild steel substrate and the corrosion rate decreased with an increase in the Cr content.     

铝基非晶纳米晶复合涂层研究

采用自动化高速电弧喷涂系统,用自行研制的粉芯丝材,在AZ91镁合金基体表面上制备出Al-Ni-Y-Co非晶纳米晶复合涂层.采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、透射电子显微镜(TEM)分析了Al-Ni-Y-Co非晶纳米晶复合涂层的微观形貌和组织结构,结果表明Al-Ni-Y-Co非晶纳米晶复合涂层是由非晶相和纳米晶化相共同组成的,涂层结构致密,孔隙率约为1.8%.Al-Ni-Y-Co非晶纳米晶复合涂层的平均显微Vickers硬度值为311.7 HV0 1,结合强度为26.8 MPa.涂层的抗磨损耐腐蚀性能优于Al涂层和AZ91镁合金基体;其相对耐磨性约为Al涂层的10倍,为AZ91镁合金的6倍;其自腐蚀电位值正于Al涂层及AZ91镁合金,自腐蚀电流密度值约为Al涂层的1/2,AZ91镁合金的1/5;其腐蚀后的表面形貌比Al涂层和AZ91镁合金平整,点蚀较少.Al-Ni-Y-Co非晶纳米晶复合涂层的耐磨防腐综合性能优异.     

Preparation,characterisation and electrochemical study of crack-free nanocrystalline electrodeposited Co-W alloy coating of high hardness

ABSTRACT

In this work, a lustrous metallic grey nanocrystalline Co-W alloy thin coating was successfully fabricated on copper substrates via galvanostatic deposition from an acidic glycine complexing bath. The impacts of various operating conditions e.g. glycine concentrations, applied current, pH and temperature on the cathodic polarisation behaviour, anodic stripping voltammetry, cathodic current efficiency (CCE%), and alloy composition were examined. This gave the opportunity to establish the operating conditions for producing various Co-W alloys. It was found that the W content in the alloy was in the range of 7.7–13.8?wt.% depending on the operating conditions. Moreover, the CCE% of the deposited alloy was characterised by relatively high values (up to 97.0%) in comparison with other baths. The XRD analysis indicates that the Co-W alloy consists of a hexagonal close-packed (hcp) Co lattice crystalline structure of nanosized grains, of average size 15.44?nm, using 25?g?L^?1 glycine, at 25°C and the highest current density tested.. The microhardness of Co-W alloy coatings is comparable to or even higher than that of hard chromium coatings (～ 963–1119?kgf mm^?2). The Co-W alloy coatings are crack-free as shown from SEM investigations. The glycine bath used for Co-W alloy codeposition is environmentally friendly.