结晶器铜板超音速火焰喷涂工艺参数对涂层结合强度的影响

文中采用超音速火焰喷涂（HVOF）在结晶器铜板表面喷涂了CoNiCrAlY涂层,研究了喷涂主要工艺参数对涂层结合强度的影响。结果表明：涂层的结合强度随着燃油流量的增大而显著增大,随着氧气流量与喷涂距离的增加结合强度均出现先增加后下降趋势,喷砂后较未喷砂结合强度大大提高。选择合适的粉末形状与粒径对于获得高质量的涂层较为重要。     

Independent control of HVOF particle velocity and temperature

Independent control of high velocity oxygen fuel (HVOF) spray particle velocity and temperature has not been possible in the past, confusing the effect of either parameter on coating properties. This study describes a method by which velocity and temperature may be varied independently. Commercial HVOF equipment that was fitted with a special conical supersonic nozzle having four distinct particle injection locations was used. The present results, which were predicted in simulations and demonstrated in experiments, revealed several pertinent facts. First, particle velocity is principally related to combustion chamber pressure and is relatively unaffected by other design or operating conditions. Second, particle temperature is related to particle residence time within the nozzle, which can be controlled by the choice of particle injection location. In these experiments, the impact velocity and temperature of stainless steel particles were controlled within the ranges 340 to 660 m/s and 1630 to 2160 K, respectively. This range of parameters produced significant variations in splat morphology, coating microstructure, and coating oxide content. Such particle control allows the effects of velocity and temperature on coating properties to be assessed and controlled independently. These results also have commercial application, potentially enabling the user to tailor particle impact velocity and temperature to achieve specific coating properties.     

工艺参数对高速电弧喷涂Al/1Cr13复合涂层组织结构的影响

用高速电弧喷涂制备Al/1Cr13复合涂层,采用3因素3水平正交试验法系统研究了电弧电流、电弧电压和喷涂距离对复合涂层的组织结构、孔隙率和氧含量的影响规律。采用扫描电镜对复合涂层的显微组织和孔隙率进行表征,采用氧氮含量分析仪测得涂层的氧含量。结果表明,在第9组喷涂参数即电弧电流为240A,电压为32V,喷涂距离为150mm的条件下制备的高速电弧喷涂Al/1Cr13复合涂层组织较致密,Al和1Cr13涂层的孔隙率最低分别为1.6%和2.2%。Al涂层氧含量显著低于1Cr13涂层,最低约为2%。     

HVOF喷涂纳米WC-12Co涂层的性能研究

为促进HVOF喷涂纳米WC-12Co涂层在工业上的应用,采用HVOF喷涂法分别制备了纳米和微米结构WC-12Co涂层.研究了涂层的结合强度,测试了两种涂层的显微硬度及耐冲蚀磨损性能,并利用扫描电镜对喷涂粉末、涂层显微组织、冲蚀表面形貌进行了分析.研究结果表明：两种涂层中纳米涂层显微硬度是普通涂层的1.5倍,最高达到1610 HV,纳米涂层中W C颗粒的分布更均匀,冲蚀率是微米级涂层的1/2左右,性能更优越.     

Hot Corrosion Behavior of HVOF Sprayed Coatings on ASTM SA213-T11 Steel

Cr₃C₂-NiCr, NiCr, WC-Co and Stellite-6 alloy coatings were sprayed on ASTM SA213-T11 steel using the HVOF process. Liquid petroleum gas was used as the fuel gas. Hot corrosion studies were conducted on the uncoated as well as HVOF sprayed specimens after exposure to molten salt at 900 °C under cyclic conditions. The thermo-gravimetric technique was used to establish the kinetics of corrosion. XRD, SEM/EDAX and EPMA techniques were used to analyze the corrosion products. All these overlay coatings showed a better resistance to hot corrosion as compared to that of uncoated steel. NiCr Coating was found to be most protective followed by the Cr₃C₂-NiCr coating. WC-Co coating was least effective to protect the substrate steel. It is concluded that the formation of Cr₂O_3, NiO, NiCr₂O₄, and CoO in the coatings may contribute to the development of a better hot-corrosion resistance. The uncoated steel suffered corrosion in the form of intense spalling and peeling of the scale, which may be due to the formation of unprotective Fe₂O₃ oxide scale.     

Microstructure and mechanical properties of HVOF sprayed nanocrystalline Cr3C2-25(Ni20Cr) coating

The objectives of this work are to deposit nanocrystalline Cr₃C₂-25(Ni20Cr) powder by thermal spraying and to compare the performance of this coating with that obtained using conventional powder. Towards that purpose, Cr₃C₂-25(Ni20Cr) powders with nanocrystalline grain size and with conventional grain size were deposited using OSU-SJS high-velocity oxyfuel (HVOF) system. The microstructural features, such as morphology of the coated surface, thickness of the coating, the interface of the coating with the substrate, distribution of various phases, and grain sizes etc, were characterized with the help of optical microscope, scanning electron microscope (SEM), and transmission electron microscope (TEM). The amount of oxide phases and pores were determined by means of image analyzer. The presence of various phases was identified by x-ray diffraction (XRD) technique. Hardness, elastic modulus, and indentation toughness were evaluated employing micro indentation technique. The results indicate the presence of three different zones containing only orthorhombic Cr₃C₂ phase, FCC NiCr phase, and mixture of Cr₃C₂ and NiCr phases in, both coatings. The grain sizes in the nanocrystalline coating were in the range of 80 to 100 nm. Nanocrystalline coating exhibits 20% increase in hardness, 40% decrease in surface roughness, and comparable fracture toughness and elastic modulus with respect to conventional coating.     

铜基体超音速火焰喷涂碳化物涂层界面研究

使用扫描电子显微镜及透射电子显微镜，对铜基体超音速火焰喷涂（HVOF）碳化物涂层的形成过程，组织结构和界面形态进行了研究。结果表明，HVOF涂层界面显微组织非常复杂，存在纳米晶，非晶和大量位错孢，非晶是粘结相在喷涂中受热，骤冷形成的，而涂层中的纳米晶来自半熔碳化物的破碎。     

高速电弧喷涂电压电流参数优化试验

采用正交试验法对影响电弧喷涂涂层性能的两个主要电参数进行了优化试验，根据涂层硬度、耐磨性、孔隙率等性能指标的测试结果，得到了相应的优化参数，电弧电压为34V，喷涂电流为180A时，喷涂涂层具有较好的综合性能，为今后高速电弧喷涂系统工艺参数的选定提供参考。     

HVOF喷涂纳米结构WC-12Co涂层的组织结构分析

纳米结构WC-12Co涂层的研究目前已受到了广泛重视,对其组织结构及影响因素的研究有利于提高涂层性能.采用HVOF工艺制备了纳米结构、多峰结构及普通微米结构3种WC-12Co金属陶瓷复合涂层,并采用SEM、XRD等对粉末及涂层的显微形貌、组织结构进行了分析;探讨了粉末在喷涂过程中的氧化脱碳机理,并指出了与之相关的影响因素.结果表明:纳米结构WC-12Co涂层结构致密,孔隙率低,与基体结合状态良好;纳米粉末在喷涂过程中比微米粉末氧化失碳严重,并发生了不同的纳米晶粒的长大;纳米粉末在喷涂过程中的氧化脱碳程度不仅与喷涂工艺有关,还在很大程度上取决于粉末本身的结构特性.     

HVOF喷涂Ni基涂层性能的研究

采用超音速火焰喷涂技术（HVOF）制备了3种镍基涂层，并对涂层的性能进行测试。结果表明：烧结粉末Ni60制备的涂层结合强度达44．6MPa、显微硬度963．8HV，均明显优于包覆粉末Ni包C、Ni包MoS2制备的涂层；Ni包C涂层孔隙率最高，达5．4％，并含有许多的未熔软质相；涂层中的镍起粘结作用，能显著提高涂层的结合强度和显微硬度；起减磨作用的MoS2和C相会明显降低涂层的结合强度。     

启闭机活塞杆表面超音速火焰喷涂WC-10Co-4Cr涂层的性能

采用超音速火焰热喷涂技术在启闭机活塞杆材料40Cr钢表面制备WC-10Co-4Cr涂层,通过扫描电镜、X射线衍射仪、显微硬度计、摩擦磨损试验机、电化学工作站等手段对涂层的基本性能进行了研究并与基材的性能进行了对比分析。结果表明:涂层的显微硬度为1 330HV0.3是基体的3.9倍,摩擦因数小于基体,其耐磨性能达到基体的145倍,涂层的耐腐蚀性能较基体也有大幅提高,并且涂层致密度高孔隙率低于0.45%,与基体之间的结合强度高于70.37MPa。将涂层应用于活塞杆表面可以大幅提高其表面性能,特别是耐磨性能及耐腐蚀性能,使得活塞杆的使用寿命提高为常用电镀铬的3倍以上。     

超音速火焰喷涂CoCrW涂层热震过程中的裂纹扩展行为

为研究CoCrW涂层的抗冷热冲击性能,采用JP5000型超音速火焰喷涂设备在高温合金表面制备了该涂层,分析了裂纹在热震过程中的扩展行为。结果表明,在800 ℃保温,25 ℃水淬的热循环条件下,经过40次热震后,涂层表面均匀地分布着网状裂纹,截面上存在垂直裂纹,但未出现涂层脱落现象;在裂纹与基体、涂层界面交汇处生成了弥散分布的以Al2O3为主要成分的氧化物。分析认为,热应力和组织应力是裂纹产生和扩展的主要驱动力,但裂纹吸收了热震过程中产生的能量,避免了应力集中,有利于提高涂层的抗热震性能。界面处弥散分布的氧化物降低了涂层与基体的结合强度,热震试验最终的失效形式可能是界面处涂层的剥离。     

粉末结构对HVOF喷涂WC-Co涂层组织性能的影响

选用4种不同WC尺度的WC-12Co粉末作为初始喂料,通过超音速火焰喷涂系统(HVOF)制备了涂层。考察了不同粉末结构对涂层沉积过程的脱碳行为和涂层组织性能的影响。结果表明:WC颗粒尺寸减小加剧了涂层脱碳行为,涂层中W2C含量增加,粘结相非晶化现象明显,涂层硬度增加,但是当WC颗粒尺寸减小到纳米尺度时,韧性下降。双峰结构涂层表现出最好的韧性同时兼备较高的硬度。     

HVOF喷涂成形纳米晶FeAl厚涂层的结构和热稳定性

采用超音速火焰喷涂(HVOF)成形工艺喷涂球磨粉末，成功制备了纳米晶FeAl厚涂层(5mm)．分别利用SEM、图像分析、TEM以及Vickers硬度表征了该涂层的微观结构，并与用相同的喷涂参数和原料粉末制备的纳米晶薄涂层(300μm)进行了比较，研究了不同的喷涂条件对涂层的结构及其硬度的影响．同时，探讨了厚涂层的热稳定性．结果表明，由于涂层中较好地保留了未融粒子中的纳米晶，从而在600℃仍能保持原有的高硬度．     

高速电弧喷涂不锈钢涂层的旋转回归试验研究

对比研究了３Ｃｒ１３不锈钢高速电弧喷涂涂层和普通电弧喷涂层的孔隙率、氧化物含量、涂层结合强度和滑动磨损性能,并采用多因素正交旋转回归设计和单因素对比试验的方法了高速电弧涂工艺参数对３Ｃｒ１３不钢涂层显微硬度的影响,用微机回归得到了喷涂工艺参数与涂层硬度之间的定量关系式。结果表明,和普通电弧喷涂涂层相比,高速电弧喷涂涂层组织致密、孔隙度低、涂层氧化物含量增多,涂层－基体界面结合强度大于４０ＭＰａ,比     

超音速火焰喷涂包覆涂层的高温氧化性能

采用超音速火焰喷涂方法制备包覆涂层,进行空气中静态和循环氧化试验和扫描电镜分析,结果表明,涂层具有较好的抗静态高温氧化性能,在900℃×100h和1000℃×100h条件下,涂层无剥落现象发生,涂层具有良好的抗循环氧化性能.     

The influence of nozzle design on HVOF exit gas velocity and coating microstructure

A simple device was constructed for determining a value for the average combustion gas velocity at the exit plane of a high-velocity oxyfuel gun. This device was used to measure the velocities of a standard factory-made barrel nozzle and a specially designed de Laval nozzle as a function of the fuel/oxygen ratio and the total mass flow rate. The Mach number of the de Laval nozzle was 1.42. The maximum combustion gas exit velocities determined for the standard and the de Laval nozzles were 1100 and 1550 m/s, respectively. The maximum velocity depends on the fuel/oxygen ratio but is independent of the total flow rate. The effect of increased combustion gas velocity on coating quality is demonstrated.     

不同参数下超音速火焰喷涂Cr_3C_2-NiCr涂层磨粒磨损性能

通过超音速火焰(HVOF)技术,采用不同的工艺参数在低碳钢表面喷涂Cr_3C_2-NiCr涂层;对所得涂层进行磨粒磨损实验.同时考察低碳钢磨损性能,比较喷涂层之间的磨损性能及其与基体的磨损性能.采用光学金相显微镜观察涂层断面的形貌,通过显微硬度计测试涂层的显微硬度.结果表明.Cr_3C_2-NiCr涂层磨损质量损失与磨程基本呈线性关系;涂层的磨损性能高于低碳钢;不同参数制备的涂层,其磨粒磨损性能也不一样,其中燃气流量为38 L/min时的涂层磨损性能较好,该条件下涂层的断面显微组织呈现层状结构,其显微硬度也较高.     

The “sonarc” process: Combining the advantages of arc and HVOF spraying

Electric arc spraying has been successfully used for many industrial applications for more than 30 years. High-velocity oxygen fuel (HVOF) spraying is another well-established technology. Coatings produced by the HVOF process, especially carbide-containing coatings, exhibit excellent quality in terms of density and hardness. One approach to obtaining both high deposition rates and dense coatings is to combine electric arc spraying and HVOF spraying in a technique known as the “Sonarc” process. This process al-lows many feed combinations through the simultaneous use of wire and powder. This paper presents the development of a prototype. Examples of composite materials and structures, their properties, and potential applications are given.     

HVOF coatings for heavy-wear, high-impact applications

The aircraft hookpoint used for an arrested landing is exposed to various forms of heavy wear and impact. Nowhere is this more true than training field landings, where the hookpoint is subjected to drag along a concrete runway for possibly thousands of feet while flying at high speeds and heavy downloads. After extensive screening, a series of materials were subjected to special impact tests and concrete wear tests. Ten coatings, applied by thermal spray, were selected for future arrestment testing on the basis of these results.