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。     

Particle Size Distribution of the Filling Powder in Cored Wires: Its Effect on Arc Behavior, In-Flight Particle Behavior, and Splat Formation

The filling powder, as a part of the feedstock in cored wires, directly influences the particle formation, in-flight particle behavior, the coating microstructure, and consequently the behavior of the desired coating, produced by twin wire arc spraying (TWAS). In this work, the effect of the particle size distribution of the filling powder in cored wires was studied. The process parameters were changed for different intervals of particle size distributions. Arc fluctuations were measured and found to be higher at smaller particle sizes. The in-flight particles showed a higher velocity when powders with smaller grain sizes were used and higher particle temperature when bigger grain sizes were used. The splats tended to form a regular disk shape in the case of smaller grain sizes. This investigation studied the important effect of using cored wires and the filling powders grain sizes on the TWAS process.     

Particle In-Flight and Coating Properties of Fe-Based Feedstock Materials Sprayed with Modern Thermal Spray Systems

New developments in the field of thermal spraying systems (increased particle velocities, enhanced process stability) are leading to improved coatings. Innovations in the field of feedstock materials are supporting this trend. The combination of both has led to a renaissance of Fe-based feedstocks. Using modern APS or HVOF systems, it is now possible to compete with classical materials for wear and corrosion applications like Ni-basis or metal-matrix composites. This study intends to give an analysis of the in-flight particle and spray jet properties achievable with two different modern thermal spraying systems using Fe-based powders. The velocity fields are measured with the Laser Doppler Anemometry. Resulting coatings are analyzed and a correlation with the particle in-flight properties is given. The experiments are accompanied by computational fluid dynamics simulations of spray jet and particle velocities, leading to a comprehensive analysis of the achievable particle properties with state-of-the-art HVOF and APS systems.     

Ni基复合WC粉末钎涂层组织及性能研究

采用气体保护的方式进行低碳钢Ni-WC涂层钎涂工艺试验;选用Ni60为基体,添加不同含量的WC颗粒(WC含量为5％、15％、25％),基体为Q235,进行磨粒磨损试验、硬度测试、金相观察及扫描电镜观察.实验结果表明:添加WC颗粒的涂层中,随着WC含量的增多,合金涂层的硬度、耐磨性有明显的提升,但不呈线性关系;当WC含量达到Ni60合金质量的15％时,硬度和耐磨性都达到最高值;超过15％后,硬度和耐磨性都会下降.     

WC颗粒尺寸对WC-CoCr涂层组织与性能的影响

喷涂粉末颗粒尺寸是影响碳化钨涂层性能的关键因素。采用HVOF工艺制备3种不同WC颗粒尺寸的WC-CoCr涂层,利用扫描电镜、X射线衍射仪、显微硬度计和颗粒冲蚀磨损试验机等对涂层的组织结构及性能进行分析,系统研究了WC颗粒尺寸对涂层组织及性能的影响。结果表明:FN-WC涂层中碳化钨分解严重,PN-WC及M-WC涂层中碳化钨颗粒少量分解。FN-WC、PN-WC及M-WC涂层孔隙率分别为2.1%、2.0%和2.3%,硬度分别为1 254、1 241和1 229HV0.3,结合强度分别为68.7、73.5和72.9 MPa。15°攻角下FN-WC、PN-WC及M-WC涂层的抗冲蚀磨损阻力Re分别为9.3×104、15.5×104和10.74×104 g/cm3,90°攻角下的抗冲蚀磨损阻力Re分别为4.68×104、4.70×104和4.26×104 g/cm3。PN-WC涂层组织更均匀,WC相分解轻微,涂层硬度分布更集中,结合强度最高,在15°攻角下表现出最好的耐冲蚀性,综合性能优异。     

氩弧熔覆Mo—Ni-Si复合涂层组织与性能的研究

以Mo、Ni、Si粉末为原料,利用氩弧熔覆技术,在廉价的Q235钢材表面原位合成了MoNiSi/Ni3Si金属硅化物复合涂层.应用扫描电镜﹑X射线衍射仪﹑显微硬度计对复合涂层的组织和性能进行了观察和分析.结果表明:熔覆层与基体呈冶金结合,且整个涂层组织均匀,无气孔和裂纹等缺陷;涂层由初生相MoNiSi﹑共晶相MoNiSi/Ni3Si和α-Fe组成;涂层的显微硬度可达1 050～1 100 HV.     

Novel Online Diagnostic Analysis for In-Flight Particle Properties in Cold Spraying

In cold spraying, powder particles are accelerated by preheated supersonic gas stream to high velocities and sprayed on a substrate. The particle velocities depend on the equipment design and process parameters, e.g., on the type of the process gas and its pressure and temperature. These, in turn, affect the coating structure and the properties. The particle velocities in cold spraying are high, and the particle temperatures are low, which can, therefore, be a challenge for the diagnostic methods. A novel optical online diagnostic system, HiWatch HR, will open new possibilities for measuring particle in-flight properties in cold spray processes. The system employs an imaging measurement technique called S-PTV (sizing-particle tracking velocimetry), first introduced in this research. This technique enables an accurate particle size measurement also for small diameter particles with a large powder volume. The aim of this study was to evaluate the velocities of metallic particles sprayed with HPCS and LPCS systems and with varying process parameters. The measured in-flight particle properties were further linked to the resulting coating properties. Furthermore, the camera was able to provide information about variations during the spraying, e.g., fluctuating powder feeding, which is important from the process control and quality control point of view.     

原位自生TiC颗粒增强金属基复合材料涂层的组织与性能

以Ni60A、Ti粉和C粉为原料，采用高频感应熔覆技术。在16Mn钢表面原位合成了TiC颗粒增强镍基复合材料涂层。借助扫描电镜、透射电镜、X射线衍射仪、显微硬度计对复合涂层的组织、结构和性能进行了分析。结果表明，熔覆层与基体呈冶金结合，无裂纹、气孔等缺陷；熔覆层组织由γ-Ni、M23C3、TiC组成，TiC大部分呈方块状，少部分呈花瓣状，颗粒尺寸为0.5-1.0μm，均弥散分布于熔覆层中，涂层的显微硬度可达980-1000HV0.2。     

Microtomographic Analysis of Splat Formation and Layer Build-Up of a Thermally Sprayed Coating

Thermal spraying is a material processing technique, which is based on the combination of thermal and kinetic energy. The used feedstock is melted in a hot flame. The melt is atomized and accelerated by means of atomization or process gases. As the formed particles hit a pre-treated substrate they are rapidly solidified and consolidate to form splats. The splats pile one-on-top-of-other forming lamellas creating the final coating. In the work presented here a combination of cored wire (WC as filling powder) and massive wire (copper) were simultaneously sprayed using the twin wire arc spraying process. 3D micro tomography was used in order to gain knowledge about splat formation and layer build-up. Due to the high attenuation coefficient of tungsten in comparison with copper and carbon, tungsten-rich particles and splats can easily be spotted in the tomogram of the coating layer. It turns out that besides irregular formed flat splats also ball-shaped particles exist in the coating layer which suggests that the spherical particles impacted on the substrate in an un-molten state. By 3D data processing tungsten-rich particles were visualized to analyze their spatial distributions and to quantify their geometric parameters. This work aims at contributing to the understanding of spraying processes.     

Latest Researches Advances of Plasma Spraying: From Splat to Coating Formation

The plasma spray process with solid feedstock, mainly ceramics powders, studied since the sixties is now a mature technology. The plasma jet and particle in-flight characterizations are now well established. The use of computer-aided robot trajectory allows spraying on industrial parts with complex geometries. Works about splat formation have shown the importance of: the substrate preheating over the transition temperature to get rid of adsorbates and condensates, substrate chemistry, crystal structure and substrate temperature during the whole coating process. These studies showed that coating properties strongly depend on the splat formation and layering. The first part of this work deals with a summary of conventional plasma spraying key points. The second part presents the current knowledge in plasma spraying with liquid feedstock, technology developed for about two decades with suspensions of particles below micrometers or solutions of precursors that form particles a few micrometers sized through precipitation. Coatings are finely structured and even nanostructured with properties arousing the interest of researchers. However, the technology is by far more complex than the conventional ones. The main conclusions are that models should be developed further, plasma torches and injection setups adapted, and new measuring techniques to reliably characterize these small particles must be designed.     

Study of the Splat Microstructure, Splat-Substrate Interface, and the Effects of Substrate Heating on the Splat Formation for Ni-Cr Particles Plasma Sprayed on to Aluminum Substrates

Roughening of the substrate, for instance by grit-blasting or etching, is often used before plasma spraying in order to provide a high degree of roughness that promotes mechanical interlocking of the sprayed coating and consequently improved adhesion. This study investigates the morphology and microstructure of NiCr splats formed on such rough Al substrates, where roughness was generated by a number of methods including grinding and etching. Cross sections of the splats and the splat-substrate interface were examined using a range of electron microscopy techniques. Localized substrate melting and chemical mixing with the splat material was observed, forming very particular structures. The formation of various oxides phases and voids was also noted and found to increase, along with the degree of the substrate melting, with increasing substrate roughness. The structures observed were related to the spray conditions and substrate morphology.     

激光熔覆混合粉末涂层的组织相容性研究

用5kW CO2激光器在16Mn钢表面激光熔覆铜基 钴基混合合金粉末、铜基 铁基混合合金粉末.观察了熔覆层的显微组织,研究了粉末配比、熔覆道次和激光功率等参数对熔覆层组织结构的影响.结果表明,一般情况下,铜基合金与其他合金粉末混合得到的熔覆层组织呈现两种完全不相容的组织形态,只有在适当的工艺参数下可以获得一定相容性的复合涂层.     

Study of the Splat Microstructure and the Effects of Substrate Heating on the Splat Formation for Ni-Cr Particles Plasma Sprayed onto Stainless Steel Substrates

The plasma spraying process is still poorly understood in term of the processes by which the coating is built up, especially coating interactions with the substrate. This present study enhances this understanding by studying, through a range of electron microscopy techniques, single NiCr splats plasma sprayed onto stainless steel substrates, which were first exposed to different heat treatments. The microstructure of the splats, particularly the splat-substrate interface, was characterized, and the formation of the observed features is discussed. Evidence of localized substrate melting and inter-mixing with the splat material was found, showing metallurgical bonding. The structures observed were also correlated to the treatment of the substrate, demonstrating how such treatments can influence the properties of the fully deposited coating by modifying the splat formation process. Most notably, heating the substrate during spraying was found to significantly modify splat formation by reducing splashing and increasing the extent of substrate melting.     

WC含量对激光熔覆NiCrBSi-WC复合涂层显微结构及力学性能的影响

目的 为盾构、勘探及采矿等高载荷严苛磨损条件下的构件表面防护提供一种新的涂层方法。方法 以激光熔覆技术为手段,在NiCrBSi粉末中混入30%~80%（体积分数）的球形WC颗粒,用以制备NiCrBSi-WC复合涂层。研究了WC颗粒含量对涂层显微组织形成、硬度、断裂韧性和耐磨性的影响规律。采用SEM分析了涂层的显微组织;通过显微维氏硬度计测试涂层的硬度;通过压痕法测试涂层的断裂韧性;采用磨粒磨损试验表征涂层的耐磨性。结果 当WC颗粒体积分数低于60%时,熔融金属的黏度较低,密度更大的WC颗粒会沉淀,导致涂层表层的WC颗粒含量较低;当WC颗粒体积分数介于60%~80%时,WC颗粒在涂层内均匀分布,涂层内无气孔及裂纹等缺陷。当WC颗粒体积分数达到80%时,熔体黏度过大,使气体难以及时逸出,在涂层内形成大量气孔。随着WC体积分数由30%上升到80%时,涂层的平均硬度由67HRC提高到85HRC。涂层的断裂韧性随WC含量的提高,出现先升高后下降的反常现象。60%WC含量的复合涂层表现出最佳的耐磨性,比滚刀常用材料H13钢提高约9倍。结论 采用常规激光熔覆技术时,添加40%~60%范围内的硬质陶瓷颗粒,可获得硬质颗粒分布均匀且耐磨性与抗冲击性能优异的复合涂层。     

化学镀Ni—P—SiC复合镀层的组织性能

对Ni-P-SiC化学复合镀层的组织性能进行了详细地研究。首先,用EDS-SEM研究了复合镀层的成分及形貌;用XRD分析了热处理后复合镀层的相组成,然后对复合镀层的硬度和耐磨性进行了系统的测定与分析。结果表明:镀液中适量的SiC及400C×1h热处理,可使复合镀层具有最大的显微硬度和最佳的耐磨性。     

Ni基高温自润滑涂层的显微结构及磨损性能

通过高能球磨、冷等静压及高频感应烧结在Ni基合金圆棒上成功制备HFIS304高温自润滑涂层。HFIS304成分(质量分数,下同)为NiCr(80/20)合金(60%),Cr2O3(20%),Ag(10%)和共晶BaF2/CaF2(10%)。HFIS304涂层组织致密,3种润滑相尺寸细小。研究表明,在室温到600℃的范围内,HFIS304涂层的耐磨性优于PS304涂层。     

激光熔覆原位析出增强颗粒热力学及显微组织研究

把理论与试验相结合,通过热力学理论计算,选择出合理的激光熔覆涂层体系,利用横流CO2激光器在铜合金表面激光熔覆Ni基复合材料涂层,原位自生陶瓷颗粒增强相.通过对激光熔覆涂层反应体系△GT的计算及XRD分析得知:TiB增强颗粒可以原位生成.利用OM、SEM和显微硬度计,分析测定涂层的显微组织形貌和截面显微硬度分布情况.结果表明:熔覆层与基体具有良好的结合界面,涂层内枝晶组织细小均匀.熔覆层平均显微硬度比基体显著提高,约为基体平均硬度值的3倍.     

超声雾化NiCoCrAITaY合金粉末微观结构及涂层高温抗氧化性能

采用超声气体雾化技术制备了ＮｉＣｏＣｒＡＩＴａＹ合金粉末,结果表明： 该合金粉末呈球形,平均粒度为３２μｍ,颗粒组织由α－Ｃｒ＋γ双相组成;采用真空等 离子喷涂方法制备的该合金粉末涂层,具有良好的抗高温氧化性能,１０００℃和 １１００℃,２００小时的静态氧化增重分别为０．３ｍｇ／ｃｍ２和０．３５ｍｇ／ｃｍ２。     

自动化纳米电刷镀复合镀层的组织和性能

采用自制的自动化电刷镀系统制备了n-Al2O3/Ni复合电刷镀层,对比研究了手动和自动纳米电刷镀镀层的组织和性能.结果表明,自动化纳米电刷镀效率高,镀层组织更致密,纳米颗粒在复合刷镀层中均匀弥散分布;镀层硬度和耐磨性能等与手动纳米刷镀层性能相近,但是,其性能分布更均匀.这是由于自动化电刷镀过程避免了人为因素影响,使得镀层金属和纳米颗粒的共沉积过程更加连续一致.