粉末原料粒径对WC-17Co涂层性能的影响（英文）

利用超音速火焰喷涂技术喷涂4种不同粒径的WC-17Co粉末,评价粉末粒径对涂层机械性能和抗磨粒磨损性能的影响。结果表明,粉末的粒径越小,在超音速焰流作用下获得的速度和温度越高,形成的涂层越致密,颗粒间的粘接强度越高,同时涂层的显微硬度也越高。WC-17Co粉末的粒径越小,获得涂层的孔隙直径越小,颗粒间的粘接缺陷越少,因此涂层的抗磨粒磨损性能越好。但是当WC-17Co粉末的粒径过于微小时,涂层的断裂韧性将受到影响。在本研究的4种粒径分布的WC-17Co粉末中,中间粒径且分布范围集中的粉末制得的涂层兼具良好的机械性能和抗磨粒磨损性能。     

WC-17Co 粉末尺寸对粒子飞行状态与涂层性能的影响分析

目的 提高碳化钨涂层的性能.方法 运用Fluent软件进行超音速火焰喷涂焰流的仿真模拟,得出喷涂距离-焰流速度、喷涂距离-焰流温度曲线.采用粒子飞行监测仪对三组不同粒度(粒子平均直径分别为21.72、32.92、42.56 μm)WC-17Co粉末在超音速火焰喷涂过程中的飞行状态进行监测,并得出喷涂距离-速度、喷涂距离-温度曲线,揭示喷涂过程中焰流速度、温度对粒子速度和温度的影响.通过扫描电镜观察分析不同粒度WC-17Co粉末撞击镍718合金基体后的扁平化程度,测量不同粒度WC-17Co涂层的孔隙率,比较涂层致密度的差异,同时采用压痕法测量涂层的硬度.结果 WC-17Co粒子飞行速度和温度随喷涂距离的增加呈先增大后减小的趋势,且粒子飞行速度和温度随粉末粒径的增大而减小,根据粉末粒径的不同,其速度峰值在690～810 m/s之间变化,温度峰值在1890～2050℃之间变化.直径越小的粒子撞击基体后的扁平率越高,扁平率在1.94～2.35之间.WC-17Co涂层的孔隙率随粒子直径的增大而升高,涂层的硬度与孔隙率成反比,涂层努氏硬度在1072～1284HK之间.结论 超音速火焰喷涂过程中,碳化钨粉末的飞行速度和温度呈先增大后减小的趋势,且飞行速度和温度与粒子直径大小成反比.碳化钨涂层的致密度与硬度随粒子直径的增大而减小.     

再生WC-Co复合粉及高耐磨性硬质合金涂层的制备

以WC-6Co废旧硬质合金块体和Co_3O_4粉末为原料,采用氧化-还原碳化法制备再生WC-12Co复合粉,将复合粉经过造粒和热处理制备再生热喷涂喂料,进而采用超音速火焰喷涂(HVOF)制备再生WC-Co硬质合金涂层,比较再生硬质合金涂层和商业购买热喷涂喂料制备涂层的显微组织、耐磨性及其机制。结果表明:当配碳量为16.70%(质量分数)时,再生复合粉的碳含量适中;制备的再生热喷涂喂料由WC和Co相组成,热喷喂料球形度好,粒径分布均匀,平均粒径为23μm;再生WC-12Co硬质合金涂层的结构致密,WC晶粒尺寸分布均匀。与商业化热喷涂粉制备涂层显微组织和性能相比,再生涂层的磨粒磨损性能明显优于商业喷涂粉制备涂层的,其根本原因是两者的磨损机制不同。     

超音速等离子与超音速火焰喷涂WC-10Co4Cr涂层的性能及磨损机理

采用超音速等离子喷涂和超音速火焰喷涂分别制备了WC-10Co4Cr金属陶瓷涂层,表征和分析了WC-10Co4Cr涂层的物相组成、微观组织结构,进行了硬度、孔隙率、结合强度及560和1120 r/min下的磨损对比试验。结果表明,超音速等离子喷涂制备的涂层的综合性能与超音速火焰喷涂制备的涂层性能相当。在560 r/min下磨损10 h,超音速等离子喷涂制备的涂层与基体的磨损量比为1∶122.15,超音速火焰喷涂制备的涂层与基体的磨损量比为1∶138.36,涂层的磨损机制主要表现为磨粒磨损。在1120 r/min下磨损10 h,超音速等离子喷涂制备的涂层与基体的磨损量比为1∶109.53,超音速火焰喷涂制备的涂层与基体的磨损量比为1∶127.44,涂层的磨损机制主要表现为磨粒磨损和疲劳磨损。     

超音速火焰喷涂碳化钨-钴涂层磨粒磨损行为

采用超音速火焰喷涂工艺在16Mn钢上制备了WC-12Co涂层,并测试了该涂层的力学性能特别是其抗磨粒磨损性能。结果表明:WC-12Co涂层的主相为碳化钨,显微硬度为(1341.0±134.3)HV,孔隙率为0.21%±0.04%。该涂层的磨损率随着磨粒硬度、磨粒粒度和加载载荷的增加而增加。当磨粒的硬度低于涂层硬度时,涂层的磨损机制以磨耗磨损为主,磨损率低;当磨粒的硬度超过涂层的硬度时,涂层的磨损以微切削为主,磨损率高。另外,WC-12Co涂层的耐磨性相对于16Mn钢也是随着磨粒的硬度变化而变化。     

镁合金表面冷喷涂纳米WC-17Co涂层及其性能

采用冷喷涂和超音速火焰喷涂(HVOF)在AZ80镁合金表面制备了纳米WC-17Co涂层。利用SEM分析了原始粉末形貌、喷涂粒子沉积行为及涂层显微结构,并采用球盘式摩擦磨损实验机考察了涂层的摩擦磨损性能。结果表明:采用冷喷涂工艺可在AZ80镁合金基体上制备出高质量的WC-17Co涂层,涂层的显微硬度为(1 380±82)HV,磨损率为9.1×10-7 mm3/Nm,其耐磨性较HVOF制备的WC-17Co涂层提高了1倍,较镁合金基材提高了3个数量级。研究表明,冷喷涂WC-17Co涂层在不对镁合金基体产生热影响的情况下,可以显著提高镁合金的表面性能,是一种新型镁合金表面强化工艺。     

等离子喷涂纳米WC-17Co涂层高温磨损性能

磨损是材料失效的主要失效形式之一,纳米WC-Co涂层技术可望成为解决重大装备关键零部件耐磨的关键技术。文中用等离子喷涂的方法制备了纳米WC-17Co涂层以及超细WC-17Co涂层,研究了涂层的高温磨损性能及失效机理。结果表明,WC-17Co纳米涂层与同成分的超细涂层相比具有较高的耐高温磨损性能。纳米涂层与超细涂层高温磨损失效机理不同,WC-17Co纳米涂层的高温磨损失效机理以磨粒磨损为主,伴随着黏着磨损,超细涂层的高温磨损失效机理以低延性开裂和黏着磨损为主,伴随有磨粒磨损。     

超音速等离子喷涂WC-17Co涂层的工艺及性能分析

以低成本压缩空气和丙烷作为工作气体,采用超音速等离子喷涂制备了WC-17Co涂层,研究了喷涂功率对涂层组织、孔隙率和相组成的影响,测试了涂层的抗压性和耐磨性.结果表明,喷涂功率显著影响粉末的熔化和脱碳程度,功率过小时,WC颗粒熔化程度低;功率过大时,WC严重脱碳生成W₂C甚至W相.喷涂功率为65 kW制备的涂层孔隙率最低（0.87%）,未出现严重脱碳产物钨,涂层具有很强的抗压入变形能力,由于高硬度WC颗粒的存在,涂层的耐磨性显著提高,其磨损量仅为基体的15%,磨损形式由基体的严重磨粒磨损+粘着磨损变为涂层的轻微磨粒磨损.     

AC-HVAF制备WC-10Co-4Cr涂层抗磨粒磨损性能研究

采用活性燃烧高速燃气(AC-HVAF)喷涂工艺制备了WC-10Co-4Cr涂层,测试了涂层的结合强度、显微硬度、气孔率以及抗磨粒磨损性能。并利用XRD对喷涂粉末及涂层进行了相结构分析,用扫描电子显微镜对喷涂粉末、磨粒磨损后的涂层表面形貌进行了观察。结果表明:在喷涂过程中,仅有很少量的WC发生合金化。涂层的结合强度和显微硬度高,组织结构致密。在相同的实验条件下,16Mn钢的磨粒磨损质量损失是WC-10Co-4Cr涂层的266倍,这表明HVAF制备的WC-10Co-4Cr涂层具有优异的抗磨粒磨损性能。     

氧燃比对爆炸喷涂WC-17Co涂层组织和性能的影响

选用WC-17Co喷涂粉末,采用爆炸喷涂工艺,通过改变乙炔和氧气流量等喷涂参数在316L钢基体上制备了4种WC/Co涂层.采用X衍射仪、扫描电镜对对涂层的相结构和微观组织进行了研究;采用灰度法测试了涂层的气孔率;采用拉伸法测试了涂层的结合强度;采用小负荷维氏硬度计测试了开裂韧性;最后采用湿砂橡胶轮磨粒磨损试验机对各涂层磨粒磨损行为进行了研究.结果显示:随着氧燃比的增加,涂层中的WC分解程度增加,涂层的硬度增加,韧性、气孔率和抗磨粒磨损性能都是先增加后降低.氧燃比为1.5时,涂层具有最优的综合力学性能.     

Effect of Atmospheric Plasma Spraying Power on Microstructure and Properties of WC-(W,Cr)2C-Ni Coatings

WC-(W,Cr)₂C-Ni coatings were prepared by atmospheric plasma spraying (APS) with different spraying powers. The effect of spraying power on microstructure, phase composition, hardness, fracture toughness, and oscillating dry friction and wear behaviors of the coatings were studied. Simultaneously, the microstructure and properties of the as-sprayed coatings were compared with those of WC-17Co coating prepared under the optimal spraying power. It was found that spraying power had significant effect on the molten degree of feedstock powder and phase composition as well as microstructure and properties of WC-(W,Cr)₂C-Ni coatings. WC-(W,Cr)₂C-Ni coating deposited at a moderate spraying power of 22.5?kW had the highest fracture toughness and the best wear resistance. WC-17Co coating obtained under the moderate spraying power had poor fracture toughness and wear resistance. Moreover, the four kinds of coatings were all dominated by subsurface cracking and removal of materials when sliding against Si₃N₄ ball under unlubricated conditions.     

Effect of Particle and Carbide Grain Sizes on a HVOAF WC-Co-Cr Coating for the Future Application on Internal Surfaces: Microstructure and Wear

The use of nanoscale WC grain or finer feedstock particles is a possible method of improving the performance of WC-Co-Cr coatings. Finer powders are being pursued for the development of coating internal surfaces, as less thermal energy is required to melt the finer powder compared to coarse powders, permitting spraying at smaller standoff distances. Three WC-10Co-4Cr coatings, with two different powder particle sizes and two different carbide grain sizes, were sprayed using a high velocity oxy-air fuel (HVOAF) thermal spray system developed by Castolin Eutectic-Monitor Coatings Ltd., UK. Powder and coating microstructures were characterized using XRD and SEM. Fracture toughness and dry sliding wear performance at three loads were investigated using a ball-on-disk tribometer with a WC-Co counterbody. It was found that the finer powder produced the coating with the highest microhardness, but its fracture toughness was reduced due to increased decarburization compared to the other powders. The sprayed nanostructured powder had the lowest microhardness and fracture toughness of all materials tested. Unlubricated sliding wear testing at the lowest load showed the nanostructured coating performed best; however, at the highest load this coating showed the highest specific wear rates with the other two powders performing to a similar, better standard.     

PREPARATION AND ITS WEAR RESISITANCE OF WC-Co/NiCrBSi METALLURGICAL BONDED COMPOSITE COATING

1-IntroductionModernengineeringaPplicationsshowthatagreatamountofdamageisrelatedtosurfaCewear.Itispossibletoprotectitagainstwearbyusingcoatingtechniques.Theadvanagesofcoatingarealongerperformancelifetimeresultingfromoptimizedmateria1combinationsandaconsequelltreductionofcost-Thesurfacepropertiesofstructuralcomponentshavesostronginfluenceontheirperformancethatseveralsurfacetechniqueshavebeenwidelyusedinindustries,suchasthermalspraying,surfaceoverlaying,deposition(PVD,CVD)[','j,andsoon-Therm…     

Effect of Feedstock Size and its Distribution on the Properties of Detonation Sprayed Coatings

The detonation spraying is one of the most promising thermal spray variants for depositing wear and corrosion resistant coatings. The ceramic (Al₂O₃), metallic (Ni-20 wt%Cr) , and cermets (WC-12 wt%Co) powders that are commercially available were separated into coarser and finer size ranges with relatively narrow size distribution by employing centrifugal air classifier. The coatings were deposited using detonation spray technique. The effect of particle size and its distribution on the coating properties were examined. The surface roughness and porosity increased with increasing powder particle size for all the coatings consistently. The feedstock size was also found to influence the phase composition of Al₂O₃ and WC-Co coatings; however does not influence the phase composition of Ni-Cr coatings. The associated phase change and %porosity of the coatings imparted considerable variation in the coating hardness, fracture toughness, and wear properties. The fine and narrow size range WC-Co coating exhibited superior wear resistance. The coarse and narrow size distribution Al₂O₃ coating exhibited better performance under abrasion and sliding wear modes however under erosion wear mode the as-received Al₂O₃ coating exhibited better performance. In the case of metallic (Ni-Cr) coatings, the coatings deposited using coarser powder exhibited marginally lower-wear rate under abrasion and sliding wear modes. However, under erosion wear mode, the coating deposited using finer particle size exhibited considerably lower-wear rate.     

Wear,erosion and corrosion resistance of HVOF-sprayed WC and Cr3C2 based coatings for electrolytic hard chrome replacement

Thermally sprayed carbide-based coatings are nowadays extensively considered as an alternative to electrolytic hard chrome (EHC) coatings to reduce the environmental impact and the overall cost associated with EHC process. In this investigation, high-velocity oxy-fuel (HVOF) spray process was employed to prepare coatings using the traditional carbide powders namely the WC-10Co4Cr, the Cr₃C₂-25NiCr and a new type of mixed carbide powder WC-40Cr₃C₂-25NiCr. The Powder deposition rate, basic mechanical properties, abrasive wear, slurry erosion and corrosion resistance of the three coatings were then compared with the EHC coating. The results show that WC-10Co4Cr coating exhibited the highest hardness, abrasive wear and slurry erosion resistance followed by WC-40Cr₃C₂-25NiCr, EHC, and Cr₃C₂-25NiCr coating. The deposition efficiency of the powders as per hierarchy was found to be WC-40Cr₃C₂-25NiCr > WC-10Co4Cr > Cr₃C₂-25NiCr and all the HVOF sprayed coatings exhibited higher corrosion resistance than EHC coating. The highest powder deposition efficiency coupled with low density, acceptable tribo-corrosion performance, as well as low post processing cost makes the HVOF sprayed WC-40Cr₃C₂-25NiCr coating a potential candidate to replace the EHC coating.     

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。     

A Comparison of Mechanical and Tribological Behavior of Nanostructured and Conventional WC-12Co Detonation-Sprayed Coatings

In the present study, WC-12Co coatings were deposited by detonation-spraying technique using conventional and nanostructured WC-12Co feedstock at four different oxy/fuel ratios (OF ratio). The coatings exhibited the presence of phases like W₂C and W due to the decarburization of the WC phase, and the proportions of these phases were higher in the nano WC-12Co coatings compared with conventional WC-12Co coatings. Coating hardness and fracture toughness were measured. The tribological performance of coatings was examined under dry sand rubber wheel abrasion wear, and solid particle erosion wear conditions. The mechanical and wear properties of coatings were influenced by degree of decarburization and more so in the case of nanostructured WC-Co coatings. The results indicate that the extent of decarburization has a substantial influence on the elastic modulus of the coating which in turn is related to the extent of intersplat cracking of the coating.     

Effect of Nozzle Geometry on the Microstructure and Properties of HVAF-Sprayed WC-10Co4Cr and Cr<Subscript>3</Subscript>C<Subscript>2</Subscript>-25NiCr Coatings

Thermally sprayed hard metal coatings are the industrial standard solution for numerous demanding applications to improve wear resistance. In the aim of improving coating quality by utilising finer particle size distributions, several approaches have been studied to control the spray temperature. The most viable solution is to use the modern high velocity air-fuel (HVAF) spray process, which has already proven to produce high-quality coatings with dense structures. In HVAF spray process, the particle heating and acceleration can be efficiently controlled by changing the nozzle geometry. In this study, fine WC-10Co4Cr and Cr₃C₂-25NiCr powders were sprayed with three nozzle geometries to investigate their effect on the particle temperature, velocity and coating microstructure. The study demonstrates that the particle melting and resulting carbide dissolution can be efficiently controlled by changing the nozzle geometry from cylindrical to convergent–divergent. Moreover, the average particle velocity was increased from 780 to over 900 m/s. The increase in particle velocity significantly improved the coating structure and density. Further evaluation was carried out to resolve the effect of particle in-flight parameters on coating structure and cavitation erosion resistance, which was significantly improved in the case of WC-10Co4Cr coatings with the increasing average particle velocity.