微束等离子喷涂制备羟基磷灰石涂层

采用微束等离子喷涂系统制备羟基磷灰石涂层,通过扫描电子显微分析(SEM)和X射线衍射分析(XRD)对涂层形貌、相组成和结晶度进行了研究.结果表明,随着喷涂电流和离子气流量的增加,羟基磷灰石粒子的熔化和撞击后的铺展更充分,在70～130 mm范围内随着喷涂距离的增加粒子熔化程度增加.适当的喷涂工艺条件下微束等离子喷涂制备羟基磷灰石涂层的结晶度可以相当或高于传统大气等离子喷涂制备的涂层,有利于涂层在体液环境中稳定性的提高.     

热处理对微束等离子喷涂羟基磷灰石涂层的影响

羟基磷灰石由于其良好的生物活性,被广泛的用作医用植入体的表面涂层材料.采用微束等离子喷涂(Microplasma Spraying,MPS)I艺在Ti-6Al-4V基体上制备羟基磷灰石涂层,通过扫描电镜(SEM)、X射线衍射(XRD)和傅里叶红外光谱(FTIR)分析了热处理对涂层相组成和表面形貌的影响规律.研究表明:微束等离子喷涂制备的羟基磷灰石涂层在经过热处理后结晶度提高,并且非晶相和杂质相转化成为HA结晶相.同时,羟基和磷酸根的完整性得到了恢复.过高的热处理温度易引起涂层裂纹等缺陷的增加,也容易造成羟基脱离造成HA分解.合理的热处理温度范围为600～700℃,保温时间为3 h.     

HA粉末粒径对微束等离子喷涂扁平粒子形貌及涂层微结构的影响

目的研究粉末粒径对微束等离子喷涂羟基磷灰石(HA)扁平粒子形貌和涂层的微观组织结构的影响。方法选取三组不同粒径范围(25～38μm、38～45μm、45～63μm)HA球形粉末,采用微束等离子喷涂方法在经镜面抛光的Ti-6Al-4V基体上收集扁平粒子,在经过喷砂处理的Ti-6Al-4V基体上沉积HA涂层。利用冷场发射扫描电子显微镜和X射线衍射仪,对扁平粒子形貌,以及涂层的形貌、相组成和择优取向进行分析。通过激光共聚焦显微镜(LSCM)观察扁平粒子的三维相貌,并对比分析扁平粒子的差异。结果微束等离子喷涂过程中,可形成几种典型形貌特征的扁平粒子,一是中间区域较厚,边缘位置较薄的扁球形;二是中间区域较薄,边缘位置较厚的圆盘状,该种扁平粒子相比于扁球形,其厚度较薄,直径较大;三是边缘位置存在"指状"溅射的圆盘状,其厚度与圆盘状扁平粒子厚度相当,但其直径范围较大。HA涂层的结晶度随着粉末粒径的减小而减小,HA的分解和非晶化逐渐增强,涂层的择优取向强度减弱,涂层中柱状晶比例减少。结论微束等离子喷涂过程中,粉末粒径对扁平粒子形貌和涂层相结构有显著影响。随着粒径的增加,扁平粒子由扁球形转变为边缘有少量"指状"溅射的圆盘状。粒径较小的HA粉末在等离子焰流中的熔化程度较高,导致涂层中分解相和非晶相含量增多,择优取向程度减小。     

微束等离子喷涂氧化锆增韧羟基磷灰石复合涂层

采用微束等离子喷涂方法,在Ti-6Al-4V基体上制备了羟基磷灰石 氧化锆(70HA-30ZrO2,质量分数,%)复合涂层.将复合涂层置于模拟体液中分别浸泡了3,7,14,28 d并观察表面磷灰石的生长情况以评价涂层生物活性.采用扫描电镜(SEM)和X射线衍射(XRD)分析技术对涂层浸泡前后的表面形貌和相组成进行了研究.结果表明,涂层中ZrO2主要以立方相存在;喷涂过程中羟基磷灰石(HA)出现了一定的分解,产生大量的α-Ca3(PO4)2杂质相.HA涂层熔化效果很好,但涂层中有未熔化的ZrO2颗粒.涂层在模拟体液中浸泡28 d后表面可以形成磷灰石,说明涂层具有很好的生物活性.     

微束等离子喷涂制备羟基磷灰石涂层微观结构的特征研究

目的 通过与大气等离子喷涂和超音速火焰啧涂的对比,研究微束等离子喷涂制备的羟基磷灰石涂层的微观组织特点.方法 以高结晶度的羟基磷灰石粉末为原料,采用三种不同的喷涂方法(微束等离子喷涂、大气等离子喷涂和超音速火焰喷涂),在Ti-6Al-4V基体上制备羟基磷灰石(HA)涂层.利用冷场发射扫描电子显微镜和X射线衍射仪,对三种涂层的形貌、相组成和择优取向进行分析.结果 与大气等离子喷涂及超音速火焰喷涂制备的涂层相比,应用该设备制备的羟基磷灰石涂层表面平整致密,无大量的气孔存在;涂层截面呈典型的层状结构,在近三分之一表面处观察到柱状晶;涂层中仅有少量的非晶相及分解相,结晶度高达90％以上.这些特征均有利于羟基磷灰石涂层在体液环境中的稳定性.结论 比较三种喷涂方法,采用微束等离子喷涂制备的羟基磷灰石涂层致密,结晶度高,杂相少,且存在择优取向的柱状晶.     

微束等离子喷涂羟基磷灰石涂层的体外生物活性研究

采用微束等离子喷涂(MPS)方法在Ti6A14V基体上制备羟基磷灰石(HA)涂层.利用扫描电镜(SEM)和x射线衍射(XRD)分析技术对HA涂层的表面形貌、相组成和结晶度进行表征,并通过模拟体液进行体外生物活性试验.结果表明,微束等离子喷涂制备的HA涂层具有一定粗糙度,存在气孔以及微裂纹.涂层存在热分解现象,涂层中含有HA、α-TCP、β-TCP和非晶相,不含CaO等杂质相.模拟体液试验表明,微束等离子喷涂工艺制备的HA涂层具有较好的生物活性和稳定性.涂层表面均有较大比例的CaP沉积层,且涂层整体保持完整,没有出现明显的剥离.     

微束等离子喷涂Mo涂层

采用微束等离子喷涂方法在Q235上制备了Mo涂层.研究喷涂电流、喷涂距离对涂层组织结构和性能的影响.采用光学显微镜观察涂层的组织结构并计算孔隙率,测试涂层的显微硬度和结合强度,并记录粉末沉积率.结果表明,在本试验条件下微束等离子喷涂电流与喷涂距离对涂层组织和性能产生较大的影响.适当工艺参数条件下粉末沉积率高于80 %,可以获得显微硬大于400 HV_(0.1),平均结合强度仍然大于40 MPa的涂层.     

微束等离子喷涂NiCrBSi涂层

采用微束等离子喷涂方法在St37低碳钢上制备了NiCrBSi涂层.研究了基材温度、等离子气体流量、喷涂距离和电流强度等工艺参数对涂层组织结构和性能的影响.采用光学显微镜观察涂层的组织结构,用Perthometers M4P 150测定涂层的表面粗糙度,以及用LECO TC316气体抽提仪检测涂层的氧含量.结果表明,在试验条件下,喷涂参数对涂层组织和性能产生较大的影响.随着电流和基材温度的增加涂层的粗糙度降低,涂层的氧含量随着基材温度和喷涂距离的增加而增加.大多数涂层的显微硬度大于600 HV0.2.尽管粒子速度较低,涂层的平均结合强度仍然大于50 MPa.     

等离子喷涂HA/(HA+TiO2)复合生物涂层的研究

用X射线衍射仪(XRD)、电子探针(EPMA)等检测手段，以大气等离子喷涂法在纯钛表面制备的羟基磷灰石HA／(HA TiO2)复合涂层及其热处理为研究对象，探讨了TiO2在羟基磷灰石复合涂层中的作用。结果表明，喷涂后的(HA TiO2)过渡层中交替分布的HA和TiO2结合致密；HA／(HA TiO2)涂层表面裂纹比对应纯HA涂层的细小，涂层内部结合致密，证实TiO2的加入具有缓和应力的作用。     

TiO2添加剂对等离子喷涂生物涂层HAP结合强度的影响

主要研究医用钛合金仿人类关节表面改性的课题。采用等离了喷涂技术,以Ｔｉ６ＡＩ４Ｖ为基体,在表面喷涂一定厚度的与肌肉容易长合的羟基磷灰石（ＨＡＰ）涂层,为了提高涂层的结合强度,加入了ＴｉＯ２添加剂。研究了不同含量的添加剂对涂层结合强度的影响,通过对涂层结合强度测试结果表明,ＴｉＯ２添加剂的加入大大提高了涂层的结合强度,而且ＴｉＯ２添加剂含量的不同,结合强度值也不同。用扫描电镜（ＳＥＭ）观察了涂层的断口形貌,发现涂层发生了部分韧化,主要是未熔的ＴｉＯ２在涂层中起到了增韧的作用。用Ｘ身线衍射（ＸＲＤ）分析了涂层的相结构,发现ＴｉＯ２添加剂直接或间接地使ＨＡＰ分解产生了新相,主要有α－ＴＣＰ等相,形成了相变韧化。     

Development of multimaterial coatings by cold spray and gas detonation spraying

The basic objective is the development of multifunctional multimaterial protective coatings using cold spraying (CS) and computer controlled detonation spraying (CCDS).As far as CS is concerned, the separate injection of each powder into different zones of the carrier gas stream is applied. Cu-Al, Cu-SiC, Al-Al₂O₃, Cu-Al₂O₃, Al-SiC, Al-Ti and Ti-SiC coatings are successfully sprayed. As to CCDS, powders are sprayed with a recently developed apparatus that is characterized by a high-precision gas supply system and a fine-dosed twin powder feeding system. Computer control provides a flexible programmed readjustment of the detonation gases energy impact on powder thus allowing selecting the optimal for each component spraying parameters to form composite and multilayered coatings. Several powders are sprayed to obtain composite coatings, specifically, among others, WC-Co-Cr + Al₂O₃, Cu + Al₂O₃, and Al₂O₃ + ZrO₂.     

Effect of steam treatment during plasma spraying on the microstructure of hydroxyapatite splats and coatings

The major problems with plasma sprayed hydroxyapatite (HA) coatings for hard tissue replacement are severe HA decomposition and insufficient mechanical properties of the coatings. Loss of crystalline HA after the high-temperature spraying is due mainly to the loss of OH⁻ in terms of water. The current study used steam to treat HA droplets and coatings during both in-flight and flattening stages during plasma spraying. The microstructure of the HA coatings and splats was characterized using scanning electron microscope, Raman spectroscopy, Fourier transform IR spectroscopy, and x-ray diffraction. Results showed that a significant increase in crystallinity of the HA coating was achieved through the steam treatment (e.g., from 58 to 79%). In addition, the effects were dependent on particle sizes of the HA feedstock, more increase in crystallinity of the coatings made from smaller powders was revealed. The Raman spectroscopy analyses on the individual splats and coatings indicate that the mechanism involves entrapping of water molecules by the individual HA droplets upon their impingement. It further suggests that the HA decomposition has already taken place before the impingement of the droplets on precoating or substrate. The improvement in crystallinity and phases, for example, from tricalcium phosphate and amorphous calcium phosphate to HA, was achieved by reversing the HA decomposition through providing extra OH⁻. Furthermore, the steam treatment during the spraying also accounts for remarkably increased adhesion strength from 9.09 to 23.13 MPa. The in vitro testing through immersing the HA coatings in simulated body fluid gives further evidence that the economic and simple steam treatment is promising in improving HA coating structure. This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials Park, OH, 2006.     

Cold gas dynamic spraying of iron-base amorphous alloy

This paper describes recent efforts to synthesize iron-base amorphous alloys coatings using cold gas dynamic spraying. Characterization of the gas-atomized iron-base (Fe-Cr-Mo-W-C-Mn-Si-Zr-B) powder shows that the powder is fully amorphous when the particle diameter is below 20 μm. The coatings produced were composed of the same microstructure as the one observed in the feedstock powder. The overall deformation suggests the occurrence of a localized deformation process at the particle/particle boundary and a possible adiabatic deformation softening inside the powder particles during splat formation. The synthesis of fully amorphous, porous-free coatings using cold gas dynamic spraying was demonstrated in this work. This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials Park, OH, 2006.     

Reactive plasma spraying of wear-resistant coatings

A method for producing wear-resistant, carbide-reinforced coatings has been investigated. A conventional low-pressure plasma gun has been modified with a downstream reactor into which carbon-containing gases are mixed, heated, and disassociated. The disassociated gas ions—H* and C* —are subsequently brought into contact with heated, molten metal matrix powders. Experiments with NiCr/Ti blends and W powders have shown that uniformly dispersed carbides such as, TiC, Cr^Cy, WC, and W2C were formed in situ on the metal precursor powders during deposition. The in situ formed particles, being formed directly from the matrices, show excellent matrix cohesion and lead to high and uniform deposit microhardnesses. The process is described and several evaluations of materials, reactive gases, and spray conditions are reported. Microanalysis of the coatings are presented, microhardness values are reported, and XRD identifies the in situ formed phases.     

Characterization of nanostructured TiN coatings fabricated by reactive plasma spraying

The nanostructured TiN coatings are fabricated by means of reactive plasma spraying micrometers titanium powders in the atmosphere, and the microstructure and performance of the coatings are analyzed by XRD, SEM and TEM. The experimental results show that the coatings are mainly composed of TiN and Ti₃O phases, and the coatings have the typical sprayed lamellae structures. In parallel to substrate surface direction, the nanoscale grains with particle diameters ranging from 60 to 120nm are observed in the coatings, and both fine equiaxed and columnar grains are found in some zones of the nanostructured TiN coatings. But in vertical to substrate surface direction, the contrary is the case. Thus it can be concluded that the TiN coatings are composed of the columnar grains, and the columnar grains are nanostructural equiaxed grains in their cross-section. In addition, a large number of deformation twins caused by the stresses concentration are found in TiN coatings. Meanwhile, the nanostructured TiN coatings have a higher bonding strength and better fracture toughness than other observed as-sprayed coatings.     

WC-based cermet coatings produced by cold gas dynamic and pulsed gas dynamic spraying processes

Due to their mechanical properties, WC-based cermet coatings are extensively used in wear-resistant applications. These coatings are usually produced using thermal spray processes. However, due to the nature and the environment of these spraying processes, the feedstock powder structure and properties suffer from decomposition, which subsequently degrade the performance of the coatings produced. The cold gas dynamic spraying process appears to be a promising alternative technique to preserve the properties of the feedstock powder during the coating preparation. Although the latter technique can minimize or eliminate the degradation of the sprayed material, the deposition of cermet using this technique is a difficult task. In this study, two types of cermet powders, the nanocrystalline (WC-15Co) and the conventional (WC-10Co4Cr) powders were deposited using the cold gas dynamic spraying and the pulsed gas dynamic spraying processes. The feedstock powders and coatings microstructures were investigated by OM, SEM and XRD, as well as their hardness. The results revealed the possibility of depositing cermet coatings onto aluminum substrates using both processes without any degradation of the carbide phase of the feedstock powder. The cold gas dynamic spraying process experienced difficulty in depositing and building up dense coatings without major defects. The pulsed gas dynamic process produced thick cermet (conventional and nanocrystalline) coatings with low porosity as long as the feedstock powder was preheated above 573 K.     

晶化处理对HA/(HA+TiO2)涂层组织结构的影响

用X射线衍射仪（XRD）、电子探针（EPMA）等检测手段，以晶化处理对大气等离子喷涂法在纯钛表面制备的HA／（HA＋TiO2）复合涂层为研究对象，探讨了晶化处理对HA／（HA＋TiO2）涂层组织结构和成分分布的影响。结果表明：晶化处理后HA／（HA＋TiO2）涂层结晶度明显提高；（HA＋TiO2）过渡层中交替分布的HA和TiO2结合致密；涂层表面裂纹比对应纯HA涂层细小，涂层内部结合致密，证实TiO2的加入具有缓和应力的作用。     

Preparation of thermal barrier coatings by ultrasonic plasma spraying

Modulated plasma arc not only can heat the powder, but also can excite ultrasonic of different frequencies and different powers. The principles and characters of the plasma arc-excited ultrasonic were described, and the ultrasonic plasma spraying was compared with normal plasma spraying. Zirconia thermal barrier coatings (TBCs) were fabricated with two kinds of method. The TBCs were studied by the optical microscope observation, SEM observation and bonding strength experiment. The results show that suitable ultrasonic changes the performance and microstructure of TBCs in evidence. And the mechanism of ultrasonic influencing the TBCs was also discussed.