爆炸喷涂WC-12Co/MoS_2复合涂层的摩擦磨损性能

为进一步提高爆炸喷涂WC-12Co涂层的耐磨性,在WC-12Co合金粉末中添加不同比例的MoS2粉末,利用爆炸喷涂技术在Q235钢表面制备了系列WC-12Co/MoS2复合涂层.采用金相显微镜、扫描电子显微镜、X射线衍射仪、显微硬度计及摩擦磨损试验机对WC-12Co/MoS2复合涂层的微观组织形貌、结构、显微硬度、摩擦磨损性能进行了研究.结果表明,MoS2均匀的分布于复合涂层中,当MoS2含量为2%时,复合涂层的硬度、致密度变化不大,但摩擦系数和磨损率大幅度下降,分别为WC-12Co涂层的50%和36%.随着MoS2含量的增加,复合涂层的摩擦系数和磨损率均呈上升趋势.     

Structure, morphology and chemical composition of sputter deposited nanostructured Cr-WS2 solid lubricant coatings

WS₂ and Cr-WS₂ nanocomposite coatings were deposited at different Cr contents (approximately 15-50 at.%) on silicon and mild steel substrates using an unbalanced magnetron sputtering system. X-ray diffraction (XRD) was used to study the structure of Cr-WS₂ coatings and the bonding structure of the coatings was studied using X-ray photoelectron spectroscopy (XPS). The characterization of different phases present in Cr-WS₂ coatings was carried out using micro-Raman spectroscopy. The XPS and Raman data indicated the formation of a thin layer of WO₃ on the surface of Cr-WS₂ coatings and the intensity of the oxide phase decreased with an increase in the Cr content, which was also confirmed using energy-dispersive X-ray analysis results. The surface morphologies of WS₂ and Cr-WS₂ coatings were examined using field emission scanning electron microscopy (FESEM) and atomic force microscopy. It has been demonstrated that incorporation of Cr in WS₂ strongly influences the structure and morphology of Cr-WS₂ coatings. The XRD and FESEM results suggested that increase in the Cr content of Cr-WS₂ coatings resulted in a structural transition from a mixture of nanocrystalline and amorphous phases to a complete amorphous phase. The cross-sectional FESEM data of WS₂ coating showed a porous and columnar microstructure. For the Cr-WS₂ coatings, a mixture of columnar and featureless microstructure was observed at low Cr contents (≤ 23 at.%), whereas, a dense and featureless microstructure was observed at high Cr contents. Detailed cross-sectional transmission electron microscopy (TEM) studies of Cr-WS₂ coatings prepared at Cr content ≤ 23 at.% indicated the presence of both nanocrystalline (near the interface) and amorphous phases (near the surface). Furthermore, high-resolution TEM data obtained from the nanocrystalline region showed inclusion of traces of amorphous phase in the nanocrystalline WS₂ phase. Potentiodynamic polarization measurements indicated that the corrosion resistance of Cr-WS₂ coatings was superior to that of the uncoated mild steel substrate and the corrosion rate decreased with an increase in the Cr content.     

Al_2O_3/MoS_2复合涂层的制备及摩擦磨损性能

以大气等离子喷涂工艺制备的Al_2O_3陶瓷涂层为模板,利用陶瓷涂层中存在的孔隙和微裂纹,采用水热反应在其内部原位合成具有润滑特性的MoS_2,制备出Al_2O_3/MoS_2的复合涂层。结果表明,通过水热反应在陶瓷涂层原有的微观缺陷中成功合成了MoS_2,合成的MoS_2固体粉末呈类球形状,并且这球状的粉末是由纳米片层状的MoS_2搭建组成的。摩擦试验结果表明,与纯Al_2O_3涂层相比,复合涂层中由于MoS_2润滑膜的形成,其摩擦因数和磨损率都显著降低,且载荷越大,复合涂层的摩擦性能越好。     

MoS2颗粒表面包覆Al2O3及其在镀层中的应用

采用非均匀形核法将Al2O3包覆到MoS2颗粒表面,提高颗粒的亲水性能。研究了溶液pH值、Al(NO3)3的摩尔浓度和预处理工艺对包覆率的影响;采用SEM及EDS分析了包覆前后MoS2颗粒的微观形貌和表面成分;通过测量接触角研究了颗粒表面的亲水性。结果表明,颗粒表面均匀包覆了一层Al(OH)3;溶液pH值对包覆率的影响最大,Al(NO3)3的摩尔浓度次之。最佳工艺为:溶液pH值为5.5,Al(NO3)3浓度为0.15mol/L,预处理过程不添加表面活性剂。随着包覆率的提高,MoS2颗粒的亲水性提高。利用包覆Al2O3的MoS2制得了Ni-P-MoS2化学复合镀层,提高了镀层中沉积粒子的均匀致密性。     

铝合金表面MoS2/Al2O3复合涂层制备及减摩性能研究

铝合金表面减摩涂层设计和制备是改善铝合金构件摩擦性能的关键技术之一。对于目前铝合金结构件易磨损的问题,本研究采用微弧氧化一步法在6063铝合金表面原位合成纳米MoS2,制备具有减摩作用的MoS2/Al2O3复合陶瓷涂层;讨论了硫盐浓度对涂层成分、形貌及摩擦性能的影响,分析了涂层减摩机理。结果表明：通过微弧氧化在6063铝合金表面成功制备出了含有MoS2的自润滑复合陶瓷涂层;涂层的摩擦系数随着硫盐浓度的升高呈现先下降后上升的趋势,当电解液中硫盐浓度为15g/L时涂层的摩擦系数为0.15,较常规微弧氧化涂层降低了76%。涂层中的MoS2分布在涂层的表面和内部,在与摩擦副接触与挤压的作用下形成均匀分布的MoS2润滑膜,表现出良好的减摩性能。     

Microstructure and mechanical properties of Al2O3-Cr2O3 composite coatings produced by atmospheric plasma spraying

Al₂O₃, Al₂O₃-Cr₂O₃ and Cr₂O₃ coatings were deposited by atmospheric plasma spraying. Phase composition of powders and as-sprayed coatings was determined by X-ray diffraction. Electron probe microanalyzer was employed to investigate the polished and fractured surface morphologies of the coatings. Mechanical properties including microhardness, fracture toughness and bending strength were evaluated. The results indicate that the addition of Cr₂O₃ is conducive to the stabilization of α-Al₂O₃. Compared with the pure Al₂O₃ and Cr₂O₃ coatings, Al₂O₃-Cr₂O₃ composite coatings show lower porosities and denser structures. Heterogeneous nucleation of α-Al₂O₃ occurs over the isostructural Cr₂O₃ lamellae and partial solid solution of Al₂O₃ and Cr₂O₃ might be occurring as well. Furthermore, grain refining and solid solution strengthening facilitate the mechanical property enhancement of Al₂O₃-Cr₂O₃ composite coatings.     

添加CeO_2对MoS_2基复合涂层摩擦学性能的影响

针对MoS_2基复合涂层耐磨性差和承载能力低的问题,以不同含量(质量分数)的CeO_2作为添加剂,采用喷涂法在GCr15钢表面制备MoS_2基复合涂层。利用摩擦磨损试验机和划痕仪分别研究涂层摩擦磨损性能和结合强度,并借助金相显微镜对涂层磨损形貌进行表征。结果表明:添加适量CeO_2可以改善涂层的摩擦磨损性能,其最佳含量为2%,此时摩擦因数和磨损量均最小,分别为0.232和0.011 3 mm~3;同时结合强度从22 N提高到28.29 N。涂层磨损量随载荷的增大而增大;而载荷小于8 N时,涂层的摩擦因数随载荷的增大而减小,当载荷大于8 N时,摩擦因数又有回升趋势。添加稀土后涂层的承载能力有明显提高。未添加稀土时,涂层产生严重剥离,并发生磨粒磨损;添加2%CeO_2后,涂层发生轻微磨粒磨损,耐磨性得到显著提高。     

Evaluation of adhesion and fatigue of MoS2-Nb solid-lubricant films deposited by pulsed-dc magnetron sputtering

The thin film deposition for tribological applications becomes more and more widespread. The tribological performance of the overlay coatings correlates with coating-substrate adhesion. Hence, it is important to measure adhesive strength. The scratch adhesion test for thin films is extensively used. In this work, MoS₂-Nb coatings deposited by closed-field unbalanced magnetron sputtering (CFUBMS) have been scratch tested in two modes. A multi-mode operation was used as sliding-fatigue, like multi-pass scratching in the same track at different fractions of critical load (unidirectional sliding) and a standard mode using progressive load operation. Failure mechanisms are discussed according to examination of response of very dense microstructure and the adhesion value. The critical load to the first failure (L_C1) was 15 N but the final adhesion value from the film and substrate interface was 120 N (L_C2) as function of the coating thinning. The coefficient of friction (COF) from the multi-scratch for MoS₂-Nb started at a very high value of around 0.067, 0.073, and 0.093 under 5, 8, and 15 N loads respectively and then drops to 0.006, 0.035, and 0.065 at the end of the 1000 cycles. The most significant finding in the test is that when the multi-scratch passes reached to 1000 cycles, micro scale fatigue failures disappeared.     

Mechanical and tribological properties of sputter deposited nanostructured Cr-WS2 solid lubricant coatings

Solid lubricant coatings of WS₂ and Cr-WS₂ (15-50 at.% Cr) prepared using an unbalanced magnetron sputtering system were evaluated for their mechanical and tribological properties. Nanoindentation results indicated that addition of Cr helped in improving the mechanical properties and the elastic recovery ability of Cr-WS₂ coatings. The adhesive strengths of Cr-WS₂ coatings were evaluated using a nanoscratch tester and from the nanoscratch profiles, critical load values and optical images, it was evident that the adhesion of Cr-WS₂ coatings increased with an increase in the Cr content. Further analysis of the nanoscratch data indicated that WS₂ coatings exhibited large amount of plastic deformation compared to Cr-WS₂ coatings which showed a combination of elastic-plastic deformation. However, micro-tribometer measurements at a load of 2 N showed that the tribological properties of Cr-WS₂ coatings deteriorated with an increase in the Cr content. For example, Cr-WS₂ coatings prepared at Cr content ≥ 33 at.% failed after a sliding distance of 1 m. On the other hand, WS₂ and Cr-WS₂ coatings prepared at low Cr contents (15-23 at.% Cr) exhibited a stable friction coefficient (50-60% relative humidity) in the range of 0.10-0.13 for a sliding distance of 14 m. Micro-Raman spectroscopy data of the worn films taken after a sliding distance of 14 m indicated the presence of WS₂ transfer films for WS₂ and Cr-WS₂ coatings prepared at low Cr contents. For Cr-WS₂ coatings with Cr content ≥ 33 at.%, the worn films consisted predominantly of WO₃. After an extended sliding distance of 50 m, Cr-WS₂ coatings (15-23 at.% Cr) outperformed WS₂ coating which failed after 20 m. Further, the coatings prepared at low Cr contents did not show any failure even after a sliding distance of 200 m. At a higher load of 7 N, Cr-WS₂ coating with 15 at.% Cr exhibited the best performance with a friction coefficient of 0.07 up to a sliding distance of 72 m. These results indicate that the amount of Cr in the WS₂ matrix needs to be controlled judiciously to obtain improved mechanical and tribological properties in Cr-WS₂ solid lubricant coatings.     

Mechanical and tribological performance of Al2O3-TiO2 coatings elaborated by flame and plasma spraying

Mechanical properties and wear rates of Al₂O₃-13 wt.% TiO₂ (AT-13) and Al₂O₃-43 wt.% TiO₂ (AT-43) coatings obtained by flame and atmospheric plasma spraying were studied. The feed stock was either ceramic cords or powders. Results show that the wear resistance of AT-13 coatings is higher than that of AT-43 and it seems that the effect of hardness on wear resistance is more important than that of toughness. Additionally, it was established that, according to conditions used to elaborate coatings and the sliding tribological test chosen, spray processes do not seem to have an important effect on the wear resistance of these coatings.     

In-situ TiB2 and Al2O3 formation by DC plasma spraying

In-situ plasma spraying (IPS) is a promising process to fabricate composite coatings with in-situ formed thermodynamically stable phases. In the present study, mechanically alloyed Al-12Si, B₂O₃ and TiO₂ powder was deposited onto an aluminum substrate using atmospheric plasma spraying (APS). It has been observed that, during the coating process, TiB₂ and Al₂O₃ are in-situ formed through the reaction between starting powders and finely dispersed in hypereutectic Al-Si matrix alloy. Also, obtained results demonstrate that in-situ reaction intensity strongly depends on spray conditions.     

等离子喷涂Cu-Al2O3梯度涂层的组织与耐磨性分析

针对纯陶瓷涂层由于结合强度低、孔隙率高、影响涂层耐磨性的实际,用等离子喷涂法制备了Cu-Al2O3梯度涂层,用电子扫描显微镜(SEM)、金相显微镜等手段对涂层进行微观组织和成分分析,用自制销盘式固定磨料磨损试验机,检测了Cu-Al2O3梯度涂层的耐磨料磨损性能.结果表明,采用等离子喷涂法制备的Cu-Al2O3梯度涂层无明显的组织突变和宏观层间界面,涂层的组织表现出宏观不均匀性和微观连续性分布特征;梯度涂层中当Al2O3含量(质量分数,%)达到80%时(GC6),涂层的耐磨性最高,约为基体的3倍,随着Al2O3含量继续增大,纯陶瓷涂层(GC7)的耐磨性有所下降.     

CuInSe2 nano-crystallite reaction kinetics using solid state reaction from Cu2Se and In2Se3 powders

The reaction mechanism and CuInSe₂ formation kinetics using a solid state reaction from Cu₂Se and In₂Se₃ powders synthesized using a heating up process were investigated using X-ray diffractomy (XRD) and transmission electron microscopy (TEM). It was observed that the CuInSe₂ phase increased gradually, accompanied with a decrease in γ-In₂Se₃ with no intermediate phase as the calcination temperature and soaking time were increased. The reaction kinetics was analyzed using the Avrami and polynomial kinetic model, suggesting that CuInSe₂ formation from Cu₂Se and In₂Se₃ powders follows a diffusion-controlled reaction with an apparent activation energy of about 122.5-182.3 kJ/mol. Cu₂Se and In₂Se₃ phases react and directly transform into CIS without the occurrence of any intermediate phase and the size of the newly formed CuInSe₂ crystallites was close to that of the Cu₂Se reactant particle based on the TEM results, which indicated that the solid reaction kinetics may be dominated by the diffusion of In³⁺ ions.     

Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere

Solid-lubricant MoS₂ coatings have been successfully applied in high vacuum and aerospace environments. However, these coatings are very sensitive to water vapor and not suitable for applications in moist environments. In this work, Cr- and T-doped MoS₂ composite coatings were developed. The results demonstrated that these composite coatings are promising for applications in high humidity environments.MoS₂-Cr and MoS₂-Ti composite coatings with different Cr or Ti content were deposited on high speed steel substrate by unbalanced magnetron sputtering. The composition, microstructure, and mechanical properties of the as-deposited MoS₂-metal composite coatings were analyzed by energy dispersive analysis of X-ray (EDX), X-ray diffraction (XRD), and nanoindentation experiments. The tribological properties of the coatings were evaluated against an alumina ball under different relative humidity atmosphere using a ball-on-disc tribometer. The MoS₂-Cr and MoS₂-Ti coatings showed a maximum hardness of 7.5 GPa and 8.4 GPa at a dopant content of 16.6 at.% Cr or 20.2 at.% Ti, respectively. The tribological test results showed that, with a small amount of Cr and/or Ti doping, the tribological properties of MoS₂ coatings under humid atmosphere could be significantly improved. The optimum doping level was found to be around 10 at.% for both MoS₂-Cr coatings and MoS₂-Ti coatings to show the best tribological properties, with both the lowest friction coefficient and wear rate. The excellent tribological properties of the MoS₂-Cr and MoS₂-Ti coatings with an appropriate metal doping level in moist atmosphere are found due to their ability to form stable transfer layer on the surface of the counterbody, which supplies lubrication for the contact surface.     

脉冲磁控溅射MoS2涂层的组织结构及摩擦学性能

采用单极性脉冲磁控溅射技术在A286基体表面制备MoS₂低摩擦系数涂层(LFC)。利用XRD、SEM等手段表征涂层的成分与微观组织;采用原位纳米力学测试系统、球-盘式摩擦磨损试验机分析涂层的力学和摩擦学性能,并探讨了脉冲偏压对涂层结构、力学和摩擦学性能的影响。结果表明,脉冲偏压由300V增加到600V,MoS₂涂层择优取向发生了(002)向(100)转变,当脉冲偏压增至800V时又恢复(002)择优取向,;随着脉冲偏压的增加,涂层的硬度及弹性模量出现先减少后增大趋势,摩擦系数在0.065~0.076范围内波动,呈现出先增加后减小趋势;偏压为800V的涂层摩擦学性能最佳,其磨损率仅为基体的13.5%。     

Study of Al2O3 coatings on AISI 316 stainless steel obtained by controlled atmosphere plasma spraying (CAPS)

The tribological behaviour of Al₂O₃ coatings on AISI 316 stainless steel, obtained by the process of controlled atmosphere plasma spraying (CAPS), is studied in this work. Atmospheric plasma spraying (APS) and high pressure plasma spraying (HPPS) were applied in order to produce these coatings. The APS coatings exhibited lower microhardness values compared to the values of HPPS coatings. Regarding the HPPS coatings it was found that plasma composition, through its heat capacity, does influence the heat transfer to particles, and, consequently, their flattening and densification process, which govern coating properties. It was revealed that tribological behaviour of coatings was influenced by the applied spraying method too. Coatings from HPPS under high-enthalpy conditions led to worst wear behaviour. In general, properties, such as microstructure, microhardness, coefficient of friction and wear resistance depended on the processing conditions such as pressure and composition of the spraying chamber atmosphere.     

Micro-scale sliding contacts on Au and Au-MoS2 coatings

The microtribological properties of Au and Au-MoS₂ coatings were examined using a nanoindentation instrument. MoS₂ was chosen for this study as an additive to Au due to its positive influence on the mechanical and tribological properties. Reciprocating microscratch tests were performed using a diamond indenter with a tip radius of 50 μm and a range of normal loads between 0.2 mN and 5.0 mN. The friction and wear results, with respect to the two coatings, were correlated to different velocity accommodation modes and levels of adhesion. It was found that the addition of 20 mol% MoS₂ to Au reduced the adhesion and limiting friction and also improved the wear resistance significantly. This coating shows potential for applications in microcomponents and microswitches due to its wear resistance, relatively low friction and good electrical conductivity.     

过渡材料对等离子喷涂Al2O3梯度陶瓷涂层性能影响

针对Al2O3陶瓷涂层结合强度低、孔隙率高的实际,选择NiAl金属间化合物和金属铜粉作为过渡材料,利用等离子喷涂制备Al2O3梯度陶瓷涂层,并对梯度涂层进行组织形貌观察,测试结合强度和孔隙率.结果表明,梯度涂层的组织表现出宏观的不均匀性和微观连续性的分布特征,NiAl和Cu是金属基体与Al2O3涂层之间过渡层的理想材料,可以有效地提高涂层的结合强度,而Cu-Al2O3梯度涂层又比NiAl-Al2O3梯度涂层结合强度高;梯度涂层的孔隙率远低于双涂层的孔隙率,在Cu-Al2O3梯度涂层中随Al2O3含量的增加,涂层的孔隙率降低,而且孔隙率低于NiAl-Al2O3梯度涂层.     

NiCrFeAl/h-BN.SiO2可磨耗封严涂层抗冲刷性能研究

利用METCO 6P-Ⅱ火焰喷涂制备NiCrFeAl/h-BN.SiO₂可磨耗封严涂层,采用SiO₂对NiCrFeAl/h-BN进行改性,改善涂层的可磨耗性。采用不同氧气/乙炔流量比(氧燃比)制备可磨耗封严涂层,并对涂层抗冲刷性能进行评价。结果显示：NiCrFeAl在喷涂过程中熔化并包覆h-BN和SiO₂粒子;随氧燃比的升高,金属相熔化更加充分,h-BN和SiO₂粒子在涂层中分布的均匀性提高,涂层表面洛氏硬度由50.8 HR15Y提高到70.3 HR15Y,结合强度升高;涂层冲刷后形貌表现出粘着磨损和磨粒磨损特征,冲刷表面粗糙度随氧燃比升高而降低,金属相对非金属相的充分包裹提高了涂层的内聚力,涂层质量损失降低,抗冲刷性能提高。     

TC4钛合金表面微弧氧化原位生长自润滑MoS2/TiO2膜层研究

钛合金表面减摩涂层的设计和制备是提升钛合金构件耐磨性能、保障服役安全的重要技术之一。针对于目前钛合金减摩涂层中减摩剂分散不均匀,易于团聚导致膜基结合力差等问题,本论文采用一步微弧氧化技术在TC4合金表面原位生长纳米MoS2颗粒,制备具有减磨作用的MoS2/TiO2复合陶瓷膜层;讨论了原位反应中硫源添加量对膜层微观结构及耐磨性能的影响。结果表明：以Na2S和Na2MoO4分别为硫源和钼源在TC4合金表面通过微弧氧化制备出了MoS2/TiO2复合陶瓷膜层;通过控制Na2S浓度可以原位生成具有小尺寸、均匀化分布的纳米MoS2颗粒,并实现对MoS2含量和形态的调控。随着Na2S浓度的增加,膜层结构逐渐致密化且表面粗糙度较低,当添加量到达60g/L时,由于硫沉淀作用导致膜层开始疏松,粗糙度增加。由于膜层表面和内部均存在均匀化分布且具有自润滑作用的MoS2颗粒,所得膜层耐磨性较传统微弧氧化膜层或直接添加MoS2颗粒所得膜层分别提高了395.4%、129.4%;同时,膜基结合力较传统微弧氧化提高了87.1%,达到了723.8N,说明了该技术在保证良好的自润滑效果同时改善了膜基结合力。该研究结果可以为钛合金耐磨涂层设计和制备提供新思路和研究方法。