WC/Co复合涂层微观结构及磨损性能研究

采用氧-煤油超音速火焰喷涂(HVOF)设备喷涂WC/Co粉末制备高抗磨损复合涂层,表征和分析了WC/Co涂层的微观组织结构、显微硬度、孔隙率和抗磨损性能,并探讨了涂层的摩擦磨损机理。结果表明:获得的WC/Co涂层的孔隙率为0.65%,平均显微硬度达1251.5 HV0.2,涂层抗磨损性能是基体ZG06Cr13Ni4Mo不锈钢的50倍以上。WC/Co涂层具有优良的抗磨损性能的根本原因在于涂层中WC的存在,它使得涂层的显微硬度得到大幅度提高,从而提高了涂层抗磨损的性能。     

HVAP 及 HVOF 工艺制备 WC10Co4Cr 复合涂层及其性能研究

目的对比研究超音速等离子喷涂(HVAP)技术与超音速火焰喷涂(HVOF)技术制备WC10Co4Cr涂层,并根据涂层组织形貌与电化学特性判断两种工艺的优劣。方法采用SEM及XRD分析WC10Co4Cr复合涂层的微观形貌和物相,在3.5%(质量分数)Na Cl溶液中对涂层进行电化学分析。结果 WC10Co4Cr涂层由较大的WC颗粒及粘结相组成,在喷涂过程中WC颗粒不断累积形成层片状结构,涂层有较小程度的失碳,形成了具有脆性的W2C。电化学极化测试表明,超音速等离子喷涂技术制备的涂层表现出优异的抗电化学腐蚀性能。结论超音速等离子喷涂技术制备的WC10Co4Cr涂层显微硬度为1197HV,孔隙率为0.50%,腐蚀电位为-0.3947 V,腐蚀电流密度为9.19×10-7A/cm2,腐蚀速率为1.01×10-2g/(m2·h),腐蚀深度为1.09×10-2mm/a,具有与超音速火焰喷涂涂层相似的耐腐蚀性能。     

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。     

灰铸铁表面喷涂WC/Co涂层的磨损特性研究

用超音速火焰喷涂方法在灰口铸铁表面进行了WC/Co涂层的喷涂,对灰铸铁表面及在其上喷涂的WC/Co涂层摩擦磨损特性进行了研究。结果表明,灰铸铁表面用超音速喷涂涂层后,耐磨性大大提高,喷涂的WC/Co涂层磨损机理表现为微观剥落,而灰铸铁基底材料则表现为磨粒磨损。     

喷涂工艺参数对热喷涂纳米镍铬碳化钨涂层微动磨损性能的影响

以纳米NiCr/WC复合粉末(其中70%的WC与30%的NiCr)(文中含量均为质量分数)为原料,采用活性燃烧超音速火焰喷涂技术制备了纳米NiCr/WC复合涂层。利用SRV高温磨损试验机进行微动磨损试验,结果显示,在其它工艺参数相同的条件下,纳米涂层在喷涂距离为200 mm条件下的耐磨性能最差,在喷涂距离为160 mm条件下的耐磨性能最好;纳米涂层在送粉率为5 rpm条件下的耐磨性能最差,在送粉率为15 rpm条件下的耐磨性能最好。此外,与综合性能优良的渗碳轴承钢20CrNi2Mo相比,所有的纳米涂层的耐磨损性能都明显优于相同温度条件下的轴承钢的耐磨损性能。     

大气等离子喷涂和超音速火焰喷涂WC-Ni涂层组织结构和性能的对比研究

采用大气等离子喷涂和超音速火焰喷涂技术在不同工艺参数下制备WC-Ni涂层。涂层的相结构和显微组织结构分别采用X射线衍射(XRD)和扫描电镜(SEM)进行表征。涂层的显微硬度、弹性模量和断裂韧性采用显微维氏硬度计进行表征。采用销盘磨损试验对涂层的磨损性能进行表征。结果表明,较大功率下等离子喷涂的涂层较致密,WC相脱碳程度较大。超音速火焰喷涂距离较小时,制备的涂层较致密,脱碳分解程度较小。相比等离子喷涂技术,超音速火焰喷涂制备的涂层中WC相的分解更少,涂层组织结构相对致密,力学性能相对较高,耐磨粒磨损性能较好。致密度相近,但脱碳程度较小的涂层耐磨性能较好。     

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。     

超音速激光沉积Ti6Al4V涂层的微观结构及耐蚀性能

超音速激光沉积技术是将激光加热与冷喷涂同步耦合的一种新型材料沉积技术。文中利用超音速激光沉积技术在中碳钢基体上制备Ti6Al4V涂层,并采用SEM、XRD、电化学腐蚀测试等手段对涂层厚度、显微组织、相成分以及耐蚀性能进行了表征分析。结果表明,在一定的激光辐照温度（即沉积区温度）范围内,涂层沉积效率、致密性以及涂层与基体之间的结合强度均随激光辐照温度的升高而增加,当激光辐照温度为800℃时,沉积效率是冷喷涂的4倍,涂层中的孔隙率仅为4.38%,涂层与基体的结合强度达75 MPa。由于低热输入的原因,涂层的物相组成与原始钛合金粉末基本一致。随着激光辐照温度的进一步提高,涂层中有TiN相的产生,不利于粉末的沉积,涂层的沉积效率、致密性以及结合强度均下降,但是在酸性腐蚀介质中,TiN的存在提高了涂层的耐蚀性能。     

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。     

冷喷涂金属基复合涂层及材料研究进展

冷喷涂是近年来一种发展十分迅速的材料固态沉积技术,其具有喷涂温度低和颗粒沉积速度高的特点,在金属基复合涂层及材料制备方面展现出了良好的应用前景。 在大量文献整理和分析的基础上,对冷喷涂金属基复合涂层及材料的最新研究进展进行了系统的介绍。 首先归纳了机械混合法、球磨法、包覆法以及造粒法等复合粉末的制备方法及其优缺点,为复合粉末的制备和选择提供了参考;其次,分类介绍了采用冷喷涂制备的铝基、镍基、铜基、钴基以及其他金属基复合涂层及材料;再次,分析了退火、激光、搅拌摩擦焊和热机械等后续处理方法对冷喷涂金属基复合涂层及材料组织结构和性能的影响,并介绍了不同后续处理方法的优缺点;最后,总结了冷喷涂金属基复合涂层及材料的潜在应用领域和存在问题。     

20Cr2Ni4A钢表面WC增强铁基涂层耐磨性能的研究

目的 制备优异的耐磨性涂层用于机械零部件表面,可有效地提高其使用寿命,减少机械设备因磨损失效而带来的各类故障.方法 以20Cr2Ni4A合金钢为基体材料,利用激光熔覆技术,制备了铁基涂层和铁基/WC复合涂层.采用X射线衍射仪(XRD)、金相显微镜、扫描电子显微镜(SEM)、HV-1000显微维氏硬度计,分别对铁基涂层和铁基/WC复合涂层的相组成、组织形貌、显微硬度进行表征.利用HRS-2M型高速往复摩擦磨损试验机对铁基涂层和铁基/WC复合涂层的磨损性能进行研究,并分析其磨损机理.结果 两种涂层的显微硬度与基体相比改善较大,其中铁基/WC复合涂层改善最为明显,表面平均硬度值为610HV.以直径为6 mm的GCr15对磨球为摩擦副,铁基涂层的平均摩擦因数为0.53左右,磨损量为0.1432 mm3,而铁基/WC复合涂层的平均摩擦因数为0.36左右,磨损量为0.05935 mm3,与铁基涂层相比,20Cr2Ni4A合金钢表面结合铁基/WC复合涂层的硬度提高了17％左右,磨损量减小了58.6％,具有良好的耐磨损性能.结论 铁基/WC复合涂层因其表面存在W2C、WC、Fe3C等物相,能够均匀分布在铁基涂层上作为耐磨骨架,显著提高了涂层的硬度和耐磨性能.     

Mechanical and tribological evaluation of PVD WC/C coatings

Five different WC/C coatings deposited by physical vapour deposition (PVD) on high speed-steel (HSS) have been evaluated with respect to their mechanical and tribological properties. For all coatings a chromium layer was deposited first to enhance coating adhesion. The carbide phase (WC) and the carbon (C) phase were deposited simultaneously by direct-current magnetron sputtering of a WC target and plasma-assisted chemical vapour deposition using hydrocarbon gas, respectively. The influence of the chromium interface layer thickness, the amount of WC phase and the flow of hydrocarbon gas on the mechanical and tribological properties of the coatings have been investigated. The coatings have been characterised with respect to their chemical composition (glow discharge optical emission spectroscopy), hardness (Vickers microhardness), morphology (scanning electron microscopy, SEM), roughness (profilometry), residual stress (beam bending), critical load (scratch testing) and abrasive wear resistance (the “dimple grinder test”). Furthermore, a ball-on-plate test was employed to obtain information about the frictional properties and sliding wear resistance of the coatings. The wear mechanisms and wear debris were analysed by SEM, Auger electron spectroscopy and electron spectroscopy for chemical analysis. All WC/C coatings displayed a thickness between 2 and 4 μm and a surface roughness in the range of 10 to 70 nm. The hardness varied between 1500 and 1800 HV. The coating residual stress was found to range from −2.5 to −0.5 GPa. The scratch test revealed a relatively high critical normal load, i.e., a relatively good adhesion of the WC/C coatings to the HSS. The abrasive wear resistance was found to be very high, in fact equally as high as that of PVD TiN. In the sliding wear test it could be seen that the coating containing the lowest amount of carbide phase (WC), i.e., the highest amount of carbon phase (C), and which had the highest compressive residual stress yielded the lowest friction and wear rate against steel. In addition, this coating was also found to yield the lowest wear rate of the counter material. In summary, a WC/C coating with overall good mechanical and tribological properties was obtained provided a relatively thin chromium layer was deposited first and if a relatively high acetylene gas flow was utilised during deposition of the WC/C layer.     

Hard and wear-resistant titanium nitride coatings for cemented carbide cutting tools by pulsed high energy density plasma

Hard and wear-resistant titanium nitride coatings were deposited by pulsed high energy density plasma technique on cemented carbide cutting tools at ambient temperature. The coating thickness was measured by an optical profiler and surface Auger microprobe. The elemental and phase compositions and distribution of the coatings were determined by Auger microprobe, x-photon electron spectroscope, and X-ray diffractometer. The microstructures of the coatings were observed by scanning electron microscope and the roughness of the sample surface was measured by an optical profiler. The mechanical properties of the coatings were determined by nanoindentation and nanoscratch tests. The tribological properties were evaluated by the cutting performances of the coated tools applied in turning hardened CrWMn steel under industrial conditions. The structural and mechanical properties of the coatings were found to depend strongly on deposition conditions. Under optimized deposition conditions, the adhesive strength of TiN film to the substrate was satisfactory with the highest critical load up to more than 90 mN. The TiN films possess very high values of nanohardness and Young’s modulus, which are near to 27 GPa and 450 GPa, respectively. The wear resistance and edge life of the cemented carbide tools were improved dramatically because of the deposition of titanium nitride coatings.     

Influence of laser cladding process on the magnetic properties of WC–FeNiCr metal–matrix composite coatings

Metal–matrix composite (MMC) coatings were deposited by laser cladding technique with direct injection of WC–FeNiCr powder onto N1310 nonmagnetic steel matrix. Laser cladding was conducted using a Trumpf6000 CO₂ laser. The morphology of WC–FeNiCr MMC coatings was characterized using scanning electron microscopy (SEM). Magnetic properties of WC–FeNiCr MMC coatings were examined by vibrating sample magnetometer (VSM) at room temperature. The influence of laser cladding process on the magnetic properties of coatings was investigated. It was found that the content of tungsten carbide and laser power have significant effect on the magnetic properties of composite coatings. The evolution of phase constitution at different laser power was identified by X-ray diffraction (XRD). The presence of an austenitic γ-(Fe, Ni), Cr_0.19Fe_0.7Ni_0.11, Fe₃W₃C, WC and W₂C phases were confirmed by the XRD analysis in the laser clad layer.     

High-Performance Molybdenum Coating by Wire–HVOF Thermal Spray Process

Coating deposition on many industrial components with good microstructural, mechanical properties, and better wear resistance is always a challenge for the thermal spray community. A number of thermal spray methods are used to develop such promising coatings for many industrial applications, viz. arc spray, flame spray, plasma, and HVOF. All these processes have their own limitations to achieve porous free, very dense, high-performance wear-resistant coatings. In this work, an attempt has been made to overcome this limitation. Molybdenum coatings were deposited on low-carbon steel substrates using wire–high-velocity oxy-fuel (W-HVOF; WH) thermal spray system (trade name HIJET 9610^®). For a comparison, Mo coatings were also fabricated by arc spray, flame spray, plasma spray, and powder-HVOF processes. As-sprayed coatings were analyzed using x-ray diffraction, scanning electron microscopy for phase, and microstructural analysis, respectively. Coating microhardness, surface roughness, and porosity were also measured. Adhesion strength and wear tests were conducted to determine the mechanical and wear properties of the as-sprayed coatings. Results show that the coatings deposited by W-HVOF have better performance in terms of microstructural, mechanical, and wear resistance properties, in comparison with available thermal spray process (flame spray and plasma spray).     

Investigation and characterization of Cr3C2-based wear-resistant coatings applied by the cold spray process

The purpose of this study was to explore the potential of the cold spray (CS) process in applying Cr₃C₂-25wt.%NiCr and Cr₃C₂-25wt%Ni coatings on 4140 alloy for wear-resistant applications. This article discusses the improvements in Cr₃C₂-based coating properties and microstructure through changes in nozzle design, powder characteristics stand off distance, powder feed rate, and traverse speed that resulted in an improved average Vickers hardness number comparable to some thermal spray processes. Cold spray process optimization of the Cr₃C₂-based coatings resulted in increased hardness and improved wear characteristics with lower friction coefficients. The improvement in hardness is directly associated with higher particle velocities and increased densities of the Cr₃C₂-based coatings deposited on 4140 alloy at ambient temperature. Selective coatings were evaluated using x-ray diffraction for phase analysis, optical microscopy (OM). and scanning electron microscopy (SEM) for microstructural evaluation, and ball-on-disk tribology experiments for friction coefficient and wear determination. The presented results strongly suggest that cold, spray is a versatile coating technique capable of tailoring the hardness of Cr₃C₂-based wear-resistant coatings on temperature sensitive substrates.     

等离子体增强磁控溅射TiN涂层与铝对摩时的摩擦磨损行为∗

铝挤压模具表面的摩擦磨损行为是影响铝制品质量和模具寿命的重要因素。为了进一步优化铝挤压模具表面耐磨涂层的沉积工艺，以 TiN 涂层为例，采用等离子体增强磁控溅射方法分别在基体偏流为 0.1 A、1.5 A、3.0 A 和 4.5 A 条件下制备 TiN 涂层，利用 XPS、SEM、AFM 和 XRD 分别测量 TiN 涂层的化学成分、表截面微观结构和相组成，利用纳米压痕仪和旋转式球-盘摩擦磨损试验机分别考察 TiN 涂层试样的综合力学性能和与铝对摩时的摩擦磨损行为。结果表明：基体偏流增加对 TiN 涂层的化学组成影响较小。随着基体偏流的增加，TiN 涂层的横截面形貌逐渐细化。涂层表面具有由岛状微凸起组成的微结构，随着基体偏流的增加，微凸起尺寸和数量逐渐减小，表面粗糙度逐渐降低。不同基体偏流条件下制备的涂层均具有明显的 TiN(111)择优生长趋势。当基体偏流从 0.1 A 增加到 1.5 A 时，TiN 涂层的晶粒尺寸明显减小，涂层的综合力学性能得到显著提高。TiN 涂层试样与铝对摩过程中主要发生粘着磨损和磨料磨损，涂层试样对铝的减摩抗磨性能与对摩过程中的铝粘着面积呈负相关。结论：基体偏流对等离子体增强磁控溅射 TiN 涂层的表截面微观结构、力学性能和摩擦磨损行为影响显著，基体偏流为 1.5 A 时制备的 TiN 涂层具有最低的摩擦因数和磨损率，分别为 0.41×10^?15 和 3.03×10^?15 m³ / (N·m)。研究结果对铝成型模具表面高性能长寿命防护涂层的研究开发具有一定的理论意义和实用价值。     

Improvement of wear resistance of wire drawing rolls with Cr-Ni-B-Si + WC thermal spraying powders

In wire drawing process, wear of rolls must be considered because of wear that influences the economics of the forming process. In this study, a nickel based matrix reinforced with WC was deposited by low cost powder welding method on low carbon steel substrates in order to determine the wear resistance of wire drawing rolls. Powder welding method includes, contrary to plasma and high velocity oxyfuel (HVOF) spraying methods, the advantages such as the single operation of powder application-fusion, simplicity, cheapness, and the ease of application. Blends of NiCrBSi and WC powders were prepared in weight proportions of WC of 40%, 45%, 50%, 55%, and 60%, respectively. Wear performance of these coatings was investigated by the dry sliding wear experiments. The wear resistance of the metal matrix composite coatings is dependent on the amount of WC. From 40% to 60%, the increase of WC is very effective on the wear resistance. The coatings with 55% and 60% of WC were worn less than the other coatings. From 55% to 60%, further increase of WC was found not to be effective for the best wear resistance. The microscopic studies of WC particles and Ni-based matrix were characterized by the scanning electron microscopy (SEM). The SEM analysis on the worn surface of coated samples shows that the matrix is considerably worn while WC particles are not considerably worn at the beginning of the wear testing. Additionally, WC particles effectively provide protection for achievement of the wear resistance at advanced periods of the wear testing.     

Cold spray deposition of a WC-25Co cermet onto Al7075-T6 and carbon steel substrates

This work focussed on the deposition of wear-resistant and corrosion-resistant WC-25Co cermet powders on carbon steel and aluminium (Al7075-T6) substrates by cold gas spraying (CGS). The unique combination of mechanical, physical and chemical properties of WC-Co cermets has led to their widespread use for the manufacture of wear-resistant parts. X-ray diffraction tests were run on the powder and coatings to determine possible phase changes during the spraying process. The bonding strength of the coatings was measured by adhesion tests (ASTM C633-08). The sliding (ASTM G99-04) and abrasive (ASTM G65-00) wear resistance of the coatings were also studied. Corrosion resistance was determined by electrochemical measurements and salt fog spray tests (ASTM B117-03). CGS achieved thick, dense and hard WC-25Co coatings on both aluminium alloy Al7075-T6 and carbon steel substrates, with excellent tribological and electrochemical properties. We thus conclude that this method is very competitive compared with conventional thermal spraying techniques, giving thick, dense and hard coatings on both aluminium alloy Al7075-T6 and carbon steel substrates, with excellent tribological and electrochemical properties.     

超音速等离子喷涂WC/Co纳米结构涂层性能研究

采用超音速等离子喷涂设备分别制备了含纳米结构和普通结构的WC／Co涂层。研究了2种涂层的结合强度、显微硬度和摩擦磨损性能，并用扫描电镜(SEM)和透射电镜(TEM)对涂层喂料(纳米WC／Co粉体)、涂层表面形貌和晶粒结构进行了分析。结果表明：含纳米结构涂层的性能优于普通的WC／Co喷涂涂层，纳米晶粒细晶强化是涂层性能提高的主要原因。