连铸机拉矫辊辊面激光重熔纳米ZrO2基涂层性能

 为了提高连铸机拉矫辊的使用寿命,在H13钢表面等离子喷涂常规级和纳米级两种规格的ZrO2涂层,并对其进行激光重熔处理。利用有限元软件ABAQUS分析热障涂层对拉矫辊温度场的影响,利用激光共焦显微镜观察涂层表面和断面的组织结构,利用场发射扫描电子显微镜（SEM）测量涂层断面的元素分布,采用Gleeble-3800热模拟试验机考查涂层的抗热冲击性,结果发现,经激光重熔之后纳米级ZrO2涂层的孔隙率和微裂纹数量都明显少于常规级ZrO2涂层,并且纳米级ZrO2涂层的抗热冲击性都优于常规级涂层。     

高铝青铜粉体超音速等离子喷涂层感应重熔后的组织及性能

为了改善涂层的组织和性能,对超音速等离子喷涂技术制备的高铝青铜涂层进行高频感应重熔处理,研究重熔后涂层的微观组织结构特征和界面结合状态.感应重熔前涂层具有层流状组织特点,含有少量氧化渣、孔隙及未完全熔融颗粒,涂层与基体间以机械结合为主.感应重熔能消除未熔颗粒和夹杂,使组织致密、均匀,组织的层流特征弱化,孔隙率有所下降.基体元素和涂层元素相互扩散,在界面形成一条明显的白亮带,呈冶金结合状态,结合牢固,涂层的结合性能有所改善.重熔后扩散带和涂层表面的硬度较高,界面结合强度也由重熔前的25.110提升至83.358 MPa.      

大力发展纳米表面工程

表面工程是当今材料科学与工程领域中一个特别重要、极具活力和备受关注的领域.纳米热喷涂开创了纳米表面工程新时代,并成为热喷涂技术新的发展方向.作者综述了纳米热喷涂涂层技术研究现状,指出未来我国应重点支持以下几个方面的研究:1.纳米热喷涂涂层成分结构设计和可控制备研究;2.有一定应用背景的或表现出优异性能的热喷涂涂层技术的...     

TiO_2纳米颗粒自清洁航空涂料的性能研究

以有机硅改性聚氨酯树脂为主要成膜物质,经氟硅烷进行表面改性后的TiO2纳米颗粒作为无机填料,制备具有自清洁功能的航空涂料。利用透射电镜(TEM)、X射线光电子能谱仪(XPS)、扫描电镜(SEM)及接触角分析仪对氟硅烷的改性机制进行了分析,讨论了改性TiO2纳米颗粒的用量对涂层疏水性及其力学性能的影响,探讨了表面微观结构和涂层疏水性能之间的关系,并分析了有效改善涂层力学性能的技术途径。结果表明,氟硅烷分子水解后相互联结,在TiO2纳米颗粒表面形成一层氟硅烷分子包覆层,提高了TiO2纳米颗粒的分散性及疏水性。随着氟硅烷改性后的TiO2纳米颗粒添加量逐渐增多,制备的有机涂层表面粗糙度逐渐增大,疏水效果越来越明显。当改性TiO2纳米颗粒的用量为24%时,涂层具有超疏水性,水接触角为151.40°,涂层表面为微纳米双重粗糙结构。通过在基底表面刷涂一层质量分数为5%~15%的硅烷偶联剂(KH-550)乙醇溶液,可以提高涂层的力学性能,达到航空涂料的基本使用要求。     

YPSZ纳米结构热喷涂粉末材料制备机理及模型研究

采用纳米颗粒浆料进行喷雾干燥、热处理的方法制备适合于热等离子体喷涂纳米结构涂层的YP-SZ纳米结构粉末原料,等离子体喷涂制备涂层。利用扫描电子显微镜、X-ray衍射分析仪、热重—差热分析对YPSZ纳米结构热喷涂粉末材料制备过程机理进行分析研究。阐明了YPSZ纳米结构热喷涂粉末材料的制备原理,得出了此过程的机理模型。     

碳化硅复合镍磷合金涂层的组织结构、显微硬度及腐蚀性能研究

镍基复合涂层是一项有望替代电镀铬涂层的先进绿色环保表面处理技术。 本文在铝合金表面制备了纯 Ni、 NiP及其与SiC复合涂层, 利用SEM、 EDS和XRD研究了Ni、 NiP及其复合涂层的微观形貌、 成分与组织结构, 利用显微硬度计与电化学工作站研究了其硬度与耐腐蚀性能。 研究结果表明： SiC 复合电镀纯镍涂层的表面较为 粗糙, SiC 复合电镀镍磷合金涂层中晶粒轮廓明显; 电沉积镍磷合金涂层的相结构包括晶体 Ni2P、 Ni12P5 和非晶 NiP。 铝合金基体表面 Ni-P 合金涂层的显微硬度显著高于纯 Ni 涂层, 引入 SiC 纳米颗粒形成复合涂层可提高其 显微硬度; SiC 颗粒有助于提高复合涂层在氯化钠溶液中的腐蚀电位, 降低腐蚀电流密度, 提高其耐蚀性能。     

钛表面激光重熔Al/Ni组合涂层的组织及其抗氧化性能

利用等离子喷涂及电弧喷涂工艺在工业纯钛表面制备Al/Ni组合涂层,并对涂层进行激光重熔处理,使涂层之间、涂层与基体之间发生冶金反应,从而得到与基体有一定结合强度的NiAl金属间化合物涂层。研究了重熔前后涂层的微观组织及NiAl金属间化合物的形成机理,并对经重熔处理后的Al/Ni/Ti试件及纯钛试件进行了800℃/60 h高温氧化试验,讨论了涂层经高温氧化后的微观组织及其对钛材抗高温氧化性能的影响与防护机理。研究表明,Ni/Al涂层经激光重熔处理后,重熔反应区由多量的呈等轴晶状的Ni_2Al_3相以及少量的呈树枝晶状的NiAl相组成。重熔处理后的涂层经高温氧化后,Ni_2Al_3相的含量有所减少且结构疏松,而NiAl相则稳定存在并最终形成了具有一定厚度的区域。激光重熔处理后的Ni/Al组合涂层对Ti基体起到了较好的抗高温氧化作用。     

纳米涂层的制备方法

论述了几种喷涂方法制备纳米涂层,包括热喷涂方法和冷喷涂方法.热喷涂方法中介绍了等离子喷涂、超音速火焰喷涂以及爆炸喷涂制备纳米涂层的技术.     

重熔处理对火焰热喷涂Ni60A涂层件疲劳性能的影响

为了研究重熔处理对火焰热喷涂件疲劳性能的影响,本文应用火焰热喷涂技术在40Cr基体上制备出Ni60A自熔性粉末合金涂层,将热喷涂件经不同时间的火焰重熔处理后,应用疲劳试验机测试了喷涂试样及基体试样的弯扭疲劳寿命,分析了试样的宏观断口及极限应力。结果表明:重熔处理时间是影响热喷涂件疲劳寿命的关键因素之一。当重熔时间不足时,涂层表面缺陷为主要裂纹源,涂层与基体的结合力不强,极限应力随裂纹的萌生波动,裂纹在涂层中的扩展以微观第一阶段为主,断口大多为瞬断面,无疲劳辉纹,热喷涂件的疲劳寿命较短;当重熔时间过长时,涂层强度有所提高,但涂层中再次形成的缺陷为主要裂纹源,极限应力波动显著,裂纹在涂层中的扩展为微观第一阶段及第二阶段,断面有较明显的疲劳辉纹;当重熔时间合理时,缺陷对喷涂件疲劳寿命的影响减弱,构件疲劳寿命显著提高。     

建筑用C/C复合材料表面ZrB_2+SiC复合粉末涂层性能的表征

运用感应等离子球化(induced plasma spherification,IPS)技术,在建筑用C/C复合材料表面制备ZrB_2+SiC复合涂层,通过实验研究Si粉含量对涂层组织和性能的影响。结果表明:涂层组织中含有主相ZrB_2与ZrSi_2,也存在部分Si。涂层中形成了复合陶瓷结构,主要由SiC含量较高的灰色颗粒与ZrB_2含量较高的白色颗粒构成。通过IPS处理,SiC被分解成C与Si的蒸气,粉末表层温度比芯部更高,表层SiC分解更快。产物中灰色与白色颗粒都发生了聚集,基体中形成了大量孔洞,不同颗粒之间紧密结合。IPS处理得到粒径小于等于20μm的球形与椭球形颗粒,部分粉末表面存在絮状物。     

A comparative Study on the Wear Behavior of Al2O3 and SiC Coated Ti-6Al-4V Alloy Developed Using Plasma Spraying Technique

This paper reports the wear characteristics of the ceramic coatings made with Al₂O₃ and also with SiC which were performed using atmospheric plasma spraying technique on the Ti-6Al-4V biomedical alloy with the aim of improving their tribological behavior. The wear behavior of the coatings was evaluated using reciprocatory wear tester with coated substrate as the flat and alumina ball as a friction partner in simulated body fluid (Hank’s solution) environment. The microstructure and phase composition of the ceramic powders and as-sprayed coatings have been characterized using scanning electron microscope and X-ray diffractometer. Porosity, microhardness, adhesion strength and roughness of the coatings were measured as they have a bearing on wear and friction behavior. The results indicate that plasma sprayed Al₂O₃ coating exhibits higher wear resistance compared to that of plasma sprayed SiC coating. The higher wear resistance of Al₂O₃ coating is attributed to the improved melting and spreading of the alumina particles onto the substrate yielding increasingly bonded splats, resulting in compact and dense microstructure with lower porosity and higher microhardness.     

冷喷涂金属涂层的耐腐蚀性能的提升方法

沉积温度低的特点使冷喷涂可避免喷涂金属粉末的氧化及对基材的热影响,是制备高致密金属涂层的有效 方法,在耐腐蚀金属涂层制备方面具有广阔的应用前景。然而在粒子高速碰撞沉积过程中,容易因粒子的塑性变 形程度不足而在粒子界面形成孔隙,相互连通的孔隙导致涂层不能隔绝腐蚀介质的渗入,因此不具备长效腐蚀防 护作用。对此,本文首先介绍了冷喷涂金属涂层的显微组织特点;其次,重点从基于热作用、力作用和热力耦合 作用的原位处理或后处理总结了改善冷喷涂金属涂层内部粒子间结合质量,进而提升金属涂层耐腐蚀性能的方法, 包括原位喷丸辅助冷喷涂方法、热处理、激光重熔、搅拌摩擦处理与热轧处理等,最后,针对当前冷喷涂耐腐蚀 涂层的发展现状,总结了亟待解决的问题和发展方向。     

紫铜上激光熔覆镍基自熔合金组织和性能研究

采用万瓦横流CO2激光器在紫铜表面熔覆镍基自熔合金熔敷层,并采用SEM、XRD、OM和显微维氏硬度计进行组织结构和硬度分析。结果表明:在紫铜表面完全可采用激光熔覆的方法制备镍基自熔合金的熔覆层,熔覆层与铜基体形成冶金结合,组织致密、晶粒细小、无裂纹、孔隙夹杂等缺陷,熔敷层内具有等轴晶、树枝晶及胞状晶等不同结构,并有WC、W2C、Ni3B等强化相颗粒。同时,与采用超音速火焰喷涂(HVAF)涂层进行对比,结果表明激光熔覆层硬度虽然低于喷涂涂层,但磨擦系数小,耐磨损性能有明显的提高。     

Study of Tribological and Mechanical Properties of A356–Nano SiC Composites

In the present investigation, the microstructural, wear, tensile and compressive properties of Al?C7Si alloy matrix nano composites have been discussed. It is noted that the composites contain higher porosity level in comparison to the matrix and increasing amount of porosity is observed with the increasing volume fraction of the reinforcement phase in the matrix. The wear sliding test disclosed that the wear resistance of the nano SiC reinforced composites is higher than that of the unreinforced alloy. It is believed that the presence of SiC particles could shield the matrix and silicon phase from directly experiencing the applied load from the counterface. It was revealed that the presence of nano-SiC reinforcement also enhanced the hardness, tensile and compressive yield strength of Al?C7Si alloy which can be attributed to small particle size and good distribution of the SiC particles and grain refinement of the matrix. The highest yield strength and UTS was obtained by the composite with 3.5?vol% SiC nano-particles. The results show that the addition of nano-particles reduces the elongation of A356 alloy.     

Effect of Laser Power on Microstructure and Wear Resistance of WCP/Ni Cermet Coating

Laser cladding nickel-based alloy coating （Ni60） and nickel-based composite coating doped with WC particles by 35 % （WCp/Ni） were produced on the low-carbon steel substrate by CO2 continuous wave laser with power of 5 kW using the injected powder technique. The effect of laser power on microstructure and wear resistance of laser cladding WCp/Ni cermet coating was investigated. The WCp/Ni alloy coating with evenly distributed WC ceramic phases and the better bond with the substrate alloy was obtained at a power of 2.2 kW. Diffusion solution reaction happened between WC particles and the substrate alloy during laser cladding, and led to the formation of block rich-tungsten carbide on the edges of the WC particles, especially at higher power. The WCp/Ni alloy coating consists of the undissolved WC particles, the block or dendritic rich-tungsten carbide, the bar-like rich-chromium carbide, and dendrite solid solution and eutectic structure among the carbides. Microhardness and wear resistance of the WCp/Ni coating at different powers were much higher or better than those of Ni60 alloy coating, and the best results were obtained at power of 2.2 kW.     

Structure and Mechanical Properties of Ni-P-Nano Al2O3 Composite Coatings Synthesized by Electroless Plating

Ni-P-nano Al2O3 composite coatings were deposited by electroless plating,and their microstructures were observed by SEM（scanning electron microscope）.The microhardness and the wear resistance of the Ni-P-nano Al2O3 composite coatings were measured using microhardness tester and block-on-ring tribometer,respectively,and the comparison with those of Ni-P coatings or Ni-P-micro Al2O3 coating was given.The influences of aging temperature on their hardness and wear resistance were analyzed.The results showed that the nano Al2O3 particles were distributed uniformly in the Ni-P-Al2O3 coatings.Among three kinds of Ni-P based coatings,the hardness and wear resistance of Ni-P-nano Al2O3 coatings were largest,and the maximum values could be obtained at 400 ℃.This indicated that the precipitation of nano Al2O3 particles would improve the hardness and wear resistance of the Ni-P coatings.     

超音速火焰喷涂CoCrW涂层的磨损特性

采用超音速火焰喷涂工艺制备了cocrw涂层,利用金刚石锥体为摩擦副,通过往复式磨损试验机测试了涂层在室温和600℃时的磨损性能,分析了涂层的磨损机理。结果表明：在室温和600℃两种温度条件下,磨损量均随着载荷的增大而增加,而涂层在同一载荷作用下,室温和600℃两种温度下的磨损量较为接近。磨损形貌则表现为磨损初期呈现明显的犁削沟槽、小片状残留物、还有小凹坑;磨损较长时间后则显示明显的粘着磨损形貌和涂层颗粒脱落坑特征。     

Fabrication and Characterization of Ni-SiC Nanocomposite Coatings on Al Substrates by Ball Impact Deposition Method

Micron-size Ni and SiC powder mixtures were used to prepare Ni-SiC nanocomposite coatings on an Al substrate by employing a high-energy ball milling technique. Ni:SiC weight ratio was varied over a wide range to explore the effect of the charge composition on the microstructure, composition, microhardness, and wear properties of the depositions. It was observed that the composition of the produced coating was correlated to the charge composition in a complex manner, which suggests that deposition rates for Ni and SiC particles significantly vary depending on the charge composition; SiC deposition rate was higher than that of Ni when Ni:SiC weight ratio was greater than 3:1. Diffusion of Al from the substrate into the Ni matrix provided evidence for the metallurgical bonding at the interface. Both microstructural and mechanical properties of the produced coatings were found to be crucially dependent on the charge composition. By increasing the SiC content in the charge from about 5 to 33 wt pct, the mechanical properties enhanced due to the dispersion strengthening effect of the incorporated SiC particles in the coatings and the crystallite size of the Ni matrix decreasing to the nanometer range. However, a further increase resulted in the formation of a coating with a poor degree of compaction. It was found that the composite coating with about 15 vol pct SiC, produced from the charge with Ni:SiC weight ratio of 2:1, showed a microhardness as high as 830 HV_0.05 along with excellent wear resistance. Despite the current sample size limitations for applying high-energy ball milling, the present findings demonstrate that the adopted technique holds good prospect for the synthesis of nanostructured metal matrix composite coatings with enhanced and tunable properties.

     

电弧喷涂含陶瓷颗粒铝基复合涂层的微结构和性能

采用5052半硬铝带分别包覆Al_2O_3、SiC、B_4C、TiC陶瓷颗粒制备的粉芯丝材进行电弧喷涂试验,制备了含陶瓷颗粒的铝基复合涂层。利用光学显微镜、XRD分析了涂层的微观组织和相结构,测试了复合涂层的显微硬度、耐磨性及耐腐蚀性。研究结果表明,制备的铝基复合涂层中含有一定数量的未熔陶瓷颗粒,涂层较为致密,无明显缺陷。含陶瓷铝基涂层的物相主要由Al和所添加的陶瓷相构成,其中在含B_4C陶瓷涂层中还存在Al_3BC、Al_4C_3和AlB_2等新相。陶瓷颗粒的加入有利于提高铝基复合涂层的显微硬度,其中B_4C的加入使涂层中基体相显微硬度提高了1.5倍,这是由于B_4C陶瓷和Al反应生成Al_3BC、Al_4C_3和AlB_2硬质相。复合涂层的耐磨性均优于纯铝涂层,摩擦磨损的形式主要为粘着磨损。动电位极化腐蚀试验表明,含SiC和TiC陶瓷涂层具有较低的腐蚀电流,耐蚀性较好,含SiC陶瓷的复合涂层出现了明显的钝化现象。