Wear resistance of Zr/WC composite coatings on Cr12MoV steel surface by electric spark deposition

Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.

Microstructure of Cu-based Amorphous Composite Coatings on AZ91D Magnesium Alloy by Laser Cladding

To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8＋20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM （scanning electron microscopy）, EDS （energy dispersive X-ray spectroscopy）, XRD （X-ray diffraction） and TEM （transmission electron microscopy） techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.

Influence of Interfacial Diffusion on Mechanical Property of Vacuum Fusion Sinter (VFS) WC-Co Composite Coating

The WC-Co composite coatings bonded tightly to steel substrate have been made by vacuum fusion sinter （VFS）. The concentration distribution of some components were measured by the electron probe, and the microstructure and morphology of VFS coatings were observed and analyzed by SEM, X-ray diffractometer and microhardness tester. Diffusion coefficient of every element was calculated by using the experimental results. The influence of the interracial diffusion on the microstructure, Vickers hardness and interracial bond strength of the VFS coatings was studied in detail. The experimental results show that there is a metallurgical bond area between the VFS WC-Co coatings and the steel substrate. The VFS coatings are characterized by the gradient hardness of the interface and the high bond strength to the steel substate, both of which are beneficial to the improvement of the wear resistance and corrosion resistance.

Influence of Heat Treatment on Microstructure and Sliding Wear Behavior of Fe-Al/WC Composite Coatings

An experimental study has been carried out to investigate the influence of heat treatment at 300 ℃,450 ℃,550 ℃,650 ℃ and 800 ℃ on the microstructure and sliding wear behavior of Fe Al/WC intermetallic composite coatings produced by high velocity arc spraying (HVAS) and cored wires. The result shows, the main phases in both as sprayed and heat treated Fe Al/WC composite coatings are iron aluminide intermetallics (Fe 3Al+FeAl) and α as well as a little oxide (Al 2O 3) and carbides (WC, W 2C, Fe 2W 2C and Fe 6W 6C). After heat treated at 450-650 ℃, dispersion strengthening of Fe 2W 2C and Fe 6W 6C will lead to a rise in microhardness of the coatings. The microhardness is likely to be the most important factor which influences the sliding wear behavior of the coatings. Increasing the microhardness through heat treatment will improve the sliding wear resistance of the Fe Al/WC composite coatings.

Oxidation behavior of Fe40Al-xWC composite coatings obtained by high-velocity oxygen fuel thermal spray

The Fe40Al-xWC(x=0,10,12,15)coatings with dense structure were successfully deposited by high-velocity oxygen fuel (HVOF)spraying of a mixture of Fe,Al and WC powders.The objective of the present work is to provide insight into the oxidation behavior of the as-deposited coatings at 650℃under 0.1 MPa flowing pure O2.The present results show differences in the oxidation behavior of Fe40Al coating and Fe40Al-xWC composite coatings.The irregular Fe2O3 layer is seen on the top surface of the composite coatings.Fe40Al coating and Fe40Al-15WC composite coating both suffer a catastrophic corrosion due to the formation of a porous structure during 24 h of oxidation.However,Fe40Al-10WC and Fe40Al-12WC composite coatings show a good oxidation resistance behavior due to their dense structure.

Microstructure and property of sub-micro WC-10 %Co particulate reinforced Cu matrix composites prepared by selective laser sintering

The WC-10%Co particulate reinforced Cu matrix composite material with a WC-Co∶Cu mass ratio of 20∶80 was successfully fabricated by selective laser sintering(SLS) process. The following optimal processing parameters were used: laser power of 700 W, scan speed of 0.06 m/s, scan line spacing of 0.15 mm, and powder layer thickness of 0.3 mm. The microstructure, composition, and phase of the laser processed material were investigated by scanning electron microscopy(SEM), X-ray diffraction(XRD), and energy dispersive X-ray(EDX) spectroscopy. The results show that the bonding mechanism of this process is liquid phase sintering. The Cu and Co act as the binder phase, while the WC acts as the reinforcing phase. The non-equilibrium effects induced by laser melting, such as high degrees of undercooling and high solidification rate, result in the formation of a metastable phase CoC0.25. The WC reinforcing particulates typically have three kinds of morphology. They are agglomerated and undissolved, incompletely separated and partially dissolved, separated and dissolved, which indicates that particle rearrangement acts as the dominant sintering mechanism for the larger WC, while dissolution-precipitation prevails for the smaller WC particles. Microhardness tester was used to determine the Vickers hardness across the cross-section of the laser sintered sample, with the average value being HV0.1268.5. However, the hardness varied considerably, which might be attributed to the WC segregation and the high solidification rate experienced by the molten pool.

Microstructure and Thermal Properties of SiCp/Cu Composites with Mo Coating on SiC Particles

SiCp/Cu composites with a compact microstructure were successfully fabricated by vacuum hot-pressing method. In order to suppress the detrimental interfacial reactions and ameliorate the interfacial bonding between copper and silicon carbide, molybdenum coating was deposited on the surface of silicon carbide by magnetron sputtering method and crystallized heat-treatment. The effects of the interfacial design on the thermo-physical properties of Si Cp/Cu composites were studied in detail. Thermal conductivity and expansion test results showed that silicon carbide particles coated with uniform and compact molybdenum coating have improved the comprehensive thermal properties of the Si Cp/Cu composites. Furthermore, the adhesion of the interface between silicon carbide and copper was significantly strengthened after molybdenum coating. Si Cp/Cu composites with a maximum thermal conductivity of 274.056 W/（m·K） and a coefficient of thermal expansion of 9 ppm/K were successfully prepared when the volume of silicon carbide was about 50%, and these Si Cp/Cu composites have potential applications for the electronic packageing of the high integration electronic devices.

激光熔覆WC/316L复合涂层结构及磨损性能

为改善激光熔覆过程中WC增强金属基复合涂层分解与分布不均匀的问题,采用激光熔覆技术制备了50%WC含量的WC/316L复合涂层,分别采用扫描电子显微镜(SEM)、显微维氏硬度计、摩擦磨损试验机表征了熔敷层的组织形貌、硬度与摩擦磨损性能。结果显示,低热输入量可以防止WC颗粒下沉,提升熔覆层厚度方向上的WC颗粒分布均匀性;但WC的平面分布均匀性较差,同时低热输入导致WC颗粒结合较弱,易发生脱落;熔覆过程中,粉末中15%的WC发生分解。研究表明,通过降低激光热输入量,可以制备WC厚度方向较为均匀的复合涂层,提升熔覆层耐磨性,但是需要优化WC平面分布均匀性与WC颗粒结合性能。

激光能量密度对65Mn钢表面Ni60A/WC复合涂层摩擦磨损性能的影响规律

目的改善旋耕刀65Mn钢的摩擦磨损性能,提高农机触土零部件的使用寿命。方法采用激光熔覆技术在65Mn钢基体表面制备Ni60A/WC复合涂层。通过改变激光功率调节激光能量密度,在不同能量密度下制备Ni60A/WC复合涂层,观察并测试不同参数下复合涂层试样的宏观形貌、微观结构、物相组成、元素分布、显微硬度及摩擦磨损特性,研究激光能量密度对Ni60A/WC复合涂层组织演变及摩擦磨损性能的影响规律和机理。结果Ni60A/WC复合熔覆层顶部主要有胞状晶和树枝晶,分布较紧密,熔覆层中部主要有树枝状晶,熔覆层底部主要为胞状晶和垂直交界面生长的枝晶,且分布均匀致密。随着激光能量密度的升高,熔覆层的熔高和熔深增加显著,WC硬质相颗粒发生分解,硬质相的数量明显减少,涂层的平均显微硬度降低。在激光能量密度为120 J/mm^(2)时,熔覆层的平均显微硬度为587.1HV1.0,相较于基体,提升了约1.8倍。此时熔覆层的平均摩擦因数最小,为0.312,相较于基体,得到显著提升,摩擦磨损机制为轻微的磨粒磨损。经田间试验测试发现,在激光能量密度为120 J/mm^(2)时制备的带有熔覆层的旋耕刀相较于无熔覆层的旋耕刀,其磨损质量降低了63%。结论通过控制激光能量密度,可以有效调控Ni60A/WC熔覆层的硬度和耐磨性,可为农机触土易磨损件的减摩耐磨表面强化改性提供理论指导。

冷喷涂Ti/WC复合涂层的组织与耐磨性研究

为解决钛及其合金磨损性能较差的问题,采用高压冷喷涂技术在Ti6Al4V合金基体上沉积了2种不同成分的Ti/WC复合涂层,通过室温下的干滑动摩擦磨损试验分别测试了基体与复合涂层的摩擦性能,并采用扫描电镜及拉曼光谱对磨损表面进行了观察与表征。结果表明,与Ti6Al4V基体的磨损率(4.06×10-7 mm3/(N·m))相比,复合涂层的磨损率降低了一个数量级,表现出优异的耐磨性。此外,涂层内WC含量的增加,提高了涂层的显微硬度,涂层的耐磨性也随之提升。在磨损轨迹表面,由TiO2、WO3以及WC碎片构成的摩擦膜能够有效避免磨球与涂层表面的直接接触,从而降低磨损程度。因此,冷喷涂Ti/WC复合涂层在钛合金磨损防护方面具有一定的应用前景。

表面机械研磨法制备Ni+WC复合涂层的耐磨性研究

为强化TA1钛合金的组织结构并提高其耐磨损性能,采用行星式机械球磨装置,在Ni与WC 2种粉末配比分别为1∶1、2∶1、3∶1、4∶1及5∶1的5种混合型增强介质下对TA1合金进行表面机械复合强化处理,在0.05 MPa氮气气氛下,设定转速为350 r/min,时间为8 h,对TA1钛合金进行表面机械变形+固相涂层复合强化处理,这种一步法表面复合强化技术具有工艺简单、能耗少、涂层选材灵活等优势。结果显示:TA1钛合金表面形成由Ni+WC涂层+形变细晶区组成的复合强化层,涂层区厚度在40μm以上,其中Ni∶WC为3∶1时所得复合涂层内部缺陷最少,且连续均匀。在5 N、10 N载荷下Ni∶WC为3∶1摩擦系数相较于其他比例低,摩擦区间更加稳定且持续时间更长。2种载荷下磨损量均较TA1原样少,其中Ni∶WC为3∶1的强化样磨痕深度、磨损量均优异于其他4种配比,因此减摩效果最为优异。此种Ni、WC混合增强介质下表层机械复合强化工艺可大幅提升TA1钛合金表层耐磨损性。混合增强颗粒涂层具有较强的减摩效果,其磨损机制主要是磨粒磨损与氧化磨损。

超音速激光沉积Cu-Al_(2)O_(3)-石墨复合涂层微观结构及耐磨损性能

目的研究不同石墨含量对超音速激光沉积Cu-Al_(2)O_(3)-石墨复合涂层的微观组织、显微硬度、耐磨损性能的影响。方法利用扫描电子显微镜、能量色谱仪、维氏硬度计、激光共聚焦扫描显微系统、X射线衍射仪、摩擦磨损测试对复合涂层的微观组织、显微硬度、耐磨损性能及磨损机制进行分析。结果随着原始粉末中镀铜石墨质量占比的增加,Cu-Al_(2)O_(3)-石墨复合涂层的沉积效率逐渐降低。基于Al_(2)O_(3)颗粒的原位喷丸效应及激光辐照的加热软化效应,复合涂层具有致密的微观组织,且复合涂层与基体界面结合良好。单一添加Al_(2)O_(3)颗粒可以将Cu涂层的硬度从108.19HV0.2提高至121.82HV0.2。随着石墨含量的增大,涂层的显微硬度逐渐降低,镀铜石墨在原始粉末中的质量分数从5%增至15%,Cu-Al_(2)O_(3)-石墨复合涂层的硬度从116.09HV0.2降至94.17HV0.2。添加石墨能够在复合涂层表面形成固体润滑层,降低复合涂层的摩擦因数,提升涂层的耐磨损性能。CuAlGr10复合涂层具有最优的耐磨损性能,磨损率为0.7×10^(−4)mm^(3)/(N·m)。此外,由于激光辐照促进了复合涂层内部颗粒间的界面结合,均匀分散在石墨润滑相中的Al_(2)O_(3)颗粒作为负载支撑和耐磨相,可进一步降低复合涂层的磨损率。结论Cu-Al_(2)O_(3)-石墨复合涂层优异的耐磨性能是润滑相石墨颗粒和硬质增强相Al_(2)O_(3)颗粒共同作用的结果,石墨的添加能够降低复合涂层的摩擦因数,提升涂层的耐磨损性能,但过量的石墨颗粒会对涂层产生割裂作用,导致增强相Al_(2)O_(3)颗粒脱离涂层,从而加剧涂层的磨损。

激光熔覆Ni/WC梯度复合涂层的组织与性能研究

目的减少涂层内部缺陷,提高Cr12MoV模具钢表面的显微硬度及耐磨性。方法采用激光熔覆技术在Cr12MoV钢上逐层制备Ni60-Ni60/25%WC(Ni/WC)梯度复合涂层。借助X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、显微硬度计、摩擦试验机和冲击试验机,研究梯度复合涂层的物相组成、微观组织、显微硬度、耐磨性与冲击韧性。结果在Cr12MoV的基体上制备Ni/WC梯度复合涂层,Ni60层与Ni60/25%WC冶金结合理想。Ni/WC梯度复合涂层的表面主要物相为γ-(Fe,Ni)、FeNi_(3)、CrB、Cr_(7)C_(3)、Cr_(23)C_(6),从Ni60层底部到顶部依次为胞状晶、柱状晶、细小的等轴枝晶。Ni/WC梯度复合涂层硬度呈梯度分布,涂层的平均硬度达到698.5HV,相较于基体提高了约55.2%。与基体相比,Ni/WC梯度复合涂层表现出更好的耐磨性能,摩擦系数和磨损率分别下降了40.92%和28.6%,其中基体表现为黏着磨损,然而涂层整体表现为磨粒磨损。但较基体而言,Ni/WC梯度复合涂层的冲击韧性值降低了32.48%,复合涂层区域表现为脆性断裂。结论Ni/WC梯度复合涂层冶金结合良好,同时与基体相比,Ni/WC梯度复合涂层可以有效提高硬度及耐磨性,但冲击韧性有所降低。

A method for preparing composite diffusion coating alloy on ceramic surface

Metallization of the ceramic surfaces of Si3N4 and Al2O3 was carried out in a composite diffusion coating vacuum furnace using a Ti-Cu composite target. The experimental process and influencing factors were discussed. Optical microscope （OM） , energy dispersive spectroscopy （EDS） , scanning electron microscopy （SEM） , X-ray diffusion （XRD） and sound emissive scratch test （SEST） were applied to evaluate the alloy layer formed on the ceramic surface. It was indicated that the diffusion coating alloy layer contained Cu, Ti, Fe, Al and Si etc. XRD result indicated that the diffusion coating alloy layer was composed of CuTi2, Cu, Si2 Ti and CuTi, Al2 TiO5 , Ti3O5. It was found that the diffusion coating alloy layer got bonded with ceramic well, and no spaUation occurred under the maximum load of 100 N. Deposited Si3N4 ceramic was welded with Q235 and the joining quality was examined. Robust joint was formed between Si3N4 ceramic/Q235. This present method has advantages in high efficiency and low cost and provides a new approach for producing ceramic and metal bond.

WC/Cu复合材料组织及烧结过程研究

研究了粉末冶金冷压—烧结法制备的WC/Cu复合材料在不同温度和时间烧结时的组织变化及WC含量对烧结过程的影响 ,分析了该材料的烧结过程。结果表明 ,WC颗粒推迟了烧结进程。烧结过程中烧结体无明显收缩 ,WC颗粒显著阻碍了晶粒长大。WC/Cu复合材料的烧结过程可分为粘结、烧结颈长大、闭孔球化。

WC/Cu复合材料制备及其高温性能

用机械合金化法结合冷变形 ,制备了WC/Cu复合材料 ,研究了冷变形后复合材料的组织特征和高温退火时的性能变化。结果表明 :烧结后的材料经冷变形 ,组织呈显著纤维状 ,WC颗粒弥散分布 ,密度明显提高 ,达到理论密度的 99 2 % ;复合材料经 6 0 0～ 90 0℃高温退火 ,强度和硬度略有下降 ,塑性则有大幅提高 ;90 0℃退火时未发生明显的再结晶 ,界面结合良好 ;

高能球磨制备纳米级WC/Cu复合粉末的研究

利用XRD、SEM等分析研究了高能球磨时间对WC/Cu复合粉末结构、形貌及相的影响。结果表明 ,随球磨时间的延长复合粉末发生细化达到纳米级粒度 ,球磨 2 4h可获得稳定晶粒尺寸 ,最小晶粒尺寸为 2 1 5nm。其中WC粉末晶粒细化速率较Cu的慢 ;球磨过程中 ,有少量的WC固溶于Cu中 ,形成Cu(WC)

激光熔覆Cu/WC_P复合涂层

采用激光熔覆表面改性方法 ,在 45号钢基体上表面熔覆Cu/WCP 复合涂层。试验研究了WC含量对熔覆复合涂层的组织特点和耐摩擦磨损性能的影响规律。研究结果表明 ,通过调整WC的加入量可获得α -Cu固溶体 +WC双相组织 ;当WC的加入量超过 30 %时 ,熔覆层中出现小圆点状的WC颗粒 ,表明WC有一定程度的熔化和溶解 ;Cu/WCP 复合熔覆层与基体金属之间存在过渡区 ,其组织为钢基体 +WC混合组织。采用 40Cr磨轮对Cu/WCP 熔覆层进行摩擦磨损试验 ,结果表明 ,WC加入量为 10 %时 ,摩擦系数与磨损量最小 ;采用硬质合金磨轮进行磨损试验 ,当WC加入量为 30 %时 ,摩擦系数最小 ,而加入量为 10 %时 。

WC/Cu大电流滑动电接触材料的研究

为了提高电接触材料的导电、导热等性能,笔者采用粉末冶金溶渗技术制备出WC/Cu滑动电接触材料,并对其显微组织和性能进行了系统研究。结果表明:WC60～90/Cu滑动电接触材料随着WC含量的增加,材料的密度由11.508 g/cm3增加到13.305 g/cm3,硬度由HB187增加到HB477,导电率由14.6 m/(Ω.mm2)下降到10.6 m/(Ω.mm2)。耐磨性随着WC含量的增加显著提高,但高Cu含量的孕育期较长。磨损机制以磨粒磨损和表面接触疲劳为主。建议使用含量为WC70/Cu30～WC80/Cu20的滑动电接触材料。

Al_2O_3/Cu-WC复合材料热变形行为及热加工图

在Gleeble 1500D热模拟机上对Al2O3/Cu-WC复合材料进行热压缩实验,研究变形温度为350-750℃、应变速率为0.01-5 s 1条件下的热变形行为。结果表明:Al2O3/Cu-WC复合材料高温流变应力—应变曲线主要以动态再结晶软化机制为特征,峰值应力随变形温度的降低或应变速率的升高而增加;热变形过程中的稳态流变应力可用双曲正弦本构关系式来描述,其激活能为229.17 kJ/mol。根据材料动态模型,计算并建立Al2O3/Cu-WC复合材料的热加工图,据此确定热变形流变失稳区及热变形过程的最佳工艺参数,其热加工温度为650-750℃,应变速率为0.1-1 s 1。