真空退火处理对掺Cr类石墨碳膜力学和摩擦学性能的影响

采用闭合场非平衡磁控溅射离子镀技术制备了掺Cr类石墨镀层,研究了真空退火温度对镀层的硬度、结合强度、摩擦系数和比磨损率的影响规律,通过X射线衍射(XRD)分析了镀层结构随退火温度的变化.结果表明:随退火温度的升高,镀层有新相生成,镀层的膜基结合强度降低,镀层硬度随温度的升高先增加后降低,退火温度为500℃时,镀层显微硬度最大;随退火温度的升高镀层摩擦系数呈现出先降低后升高的变化趋势,比磨损率逐渐增大.     

石墨靶电流对类石墨镀层摩擦性能的影响

用非平衡磁控溅射离子镀技术制备含铬类石墨镀层,研究了石墨靶电流对磁控溅射法制备类石墨镀层摩擦性能的影响.通过扫描电镜、原子力显微镜、透射电镜等分析了镀层的表面形貌与组织.结果表明:所制备镀层的硬度随着石墨靶电流的升高而增加;镀层的摩擦系数和比磨损率随靶电流的增大呈现先降后升的趋势;扫描电镜和原子力显微镜图片分析表明镀层表面呈典型的岛团状聚集态,且随着石墨靶电流增大,镀层表面岛团状尺寸变大、镀层表面粗糙度随之增大.用高分辨透射电镜分析显示:靶电流较小时碳层中出现Cr元素富集区,随着石墨靶电流的增大,表面层中的Cr弥散分布.     

磁控溅射类石墨镀层的微观组织观察与分析

利用非平衡磁控溅射系统制备了含微量Cr的类石墨镀层,使用四点探针法测量所制备镀层的电阻率,测试结果表明所制备镀层工作层为类石墨层。使用SEM观察了镀层形貌,使用TEM及HRTEM观察了镀层的微观组织并利用选区电子衍射分析了镀层相结构,观察和分析结果表明:镀层表面质量良好,镀层的纯Cr金属底层为柱状晶结构,过渡层的晶体结构为非晶相中嵌有Cr纳米晶结构;工作层为非晶结构。测定了镀层的硬度、结合力,以及在不同载荷下的摩擦因数和比磨损率,测试结果表明:所制备镀层具有高硬度、高结合力、低摩擦因数和低比磨损率,且高载下比低载下有更低的摩擦因数。分析和讨论的结果还表明:工作层的非晶结构,是使所研究镀层具有高硬度、高结合力、低摩擦因数、低磨损率低的主要原因。     

碳基非晶镀层的纳米晶诱发机理及其摩擦学性能研究

采用磁控溅射离子镀技术制备了一组不同Cr含量的碳基离子镀层,利用XRD、SEM、TEM、XPS及Raman光谱对镀层的微观结构进行了表征,并分析了微观结构对镀层的力学性能及摩擦学性能的影响。实验结果表明:随着Cr含量的增加,碳基镀层从典型的非晶结构转变为纳米晶/非晶复合结构,sp2杂化键含量逐渐增加,sp3杂化键含量逐渐减少,并且碳基镀层的硬度和内应力均随着Cr含量的增加而呈现减小的趋势。微量的金属Cr掺杂可有效地降低镀层的摩擦系数和比磨损率。过量的Cr掺杂虽有利于sp2杂化键含量的提高,但金属相的弥散分布导致了碳基镀层摩擦系数和比磨损率的增大,摩擦学性能变差。     

TC4合金表面Cu/石墨复合镀层的摩擦磨损行为

采用无氰电镀工艺在TC4合金表面制备了Cu/石墨复合镀层,研究了镀层的组织结构和摩擦磨损行为。结果表明,采用无氰电镀方法能够在TC4合金表面制备出组织致密且与基体结合紧密的Cu/石墨复合镀层,但增加镀层中石墨的含量会降低镀层与基体合金的结合强度,并导致硬度小幅下降。摩擦磨损实验结果表明,Cu/石墨复合镀层具有优良的摩擦磨损防护性能,归因于石墨有效降低了镀层的摩擦系数和磨损率;对镀层磨损形貌、磨损产物和摩擦系数的综合分析结果表明,纯铜镀层的摩擦磨损机制主要为犁削磨损、黏着磨损和剥层磨损,Cu/石墨复合镀层的磨损机制为轻微的削层磨损和疲劳磨损。     

碳纳米管复合镀层在不同摩擦组合下的摩擦学行为

对CVD法制备的碳纳米管进行了表面改性和修饰,然后通过化学共沉积方法制备了高硬度的碳纳米管复合镀层,并研究了碳纳米管复合镀层在不同摩擦组合下的摩擦学行为.结果表明:经过改性处理后的碳纳米管表面拥有丰富的表面官能团,这使大量的碳纳米管复合于镀层中,从而导致了镍磷复合镀层的硬度显著提高,达到946 HV.摩擦实验得出,在润滑状态下以钢环为摩擦副,碳纳米管增强的镍磷复合镀层比传统耐磨材料SiC增强的镍磷复合镀层具有更低的摩擦系数和磨损率.此外,不同摩擦组合下的摩擦结果表明,SiC复合镀层相互摩擦时尽管拥有较低的磨损率,但其摩擦系数仍然较高,而碳纳米管复合镀层相互摩擦时表现出最低的摩擦系数和磨损率,其摩擦系数和磨损率分别为0.108 7和1.49×10-3 g/m.     

Mo含量对CrMoAlN薄膜微观结构和摩擦磨损性能的影响

采用非平衡磁控溅射离子镀技术在M2工具钢和单晶Si表面沉积多元CrMoAlN纳米多层薄膜.利用EDS,SEM,XRD,XPS,纳米压痕仪和销盘磨损试验仪研究Mo含量对CrMoAlN薄膜成分、表面和截面形貌、相结构、化学价态、显微硬度和摩擦性能的影响.结果表明,不同Mo含量的CrMoAlN薄膜均为fcc结构,Mo代替了Cr Al N晶格中部分Cr或Al的位置,形成了以fcc-Cr N相为基础的CrMoAlN置换固溶体.随着Mo含量提高,CrMoAlN薄膜表面颗粒尺寸明显减小,截面柱状晶结构逐渐消失.CrMoAlN薄膜的显微硬度和弹性模量随着Mo含量的增加而提高,摩擦系数和磨损率随着Mo含量的提高而降低.Mo含量为19.47%(原子分数)时,显微硬度与弹性模量均达到最大值29.70 GPa和427.53 GPa,摩擦系数和磨损率达到最小值0.271和1.2×10-16m3/(N·m).     

石墨对镍基固体润滑涂层组织与性能的影响

采用超音速火焰喷涂技术在45钢表面制备了含石墨和MoS2双组元润滑剂的Ni基固体润滑涂层,研究加入石墨(含量0%～9wt%)对涂层组织和性能的影响及双组元润滑剂在涂层中的相互作用.结果表明,随着石墨含量的增加,涂层中的孔隙增加,结合强度降低,摩擦系数和磨损率先下降后上升.石墨含量为3.0%时,石墨与MoS2的协调作用有利于保障涂层摩擦表面润滑相的连续形成,涂层摩擦系数为0.26,磨损率为0.82×10-3 mg·s-1,减磨性最优.     

碳靶电流对掺铬类石墨镀层结构和性能的影响研究

目的采用物理气相沉积磁控溅射方法,通过控制碳靶电流改变掺铬类石墨镀层的碳含量,在高速钢基体上制备不同厚度的掺铬类石墨镀层,以探究碳含量对掺铬类石墨镀层结构和性能的影响。方法采用压痕法和划痕法对镀层的膜基结合强度进行评价。采用维氏显微硬度计对镀层的硬度进行分析。采用ST-2258A四探针测试仪测量镀层的电导率。使用扫描电子显微镜对镀层的微观结构进行分析。使用摩擦磨损仪对镀层的摩擦学性能进行探究。结果随着碳靶电流的增加,掺铬类石墨镀层的截面柱状化现象越来越明显,表面团簇颗粒直径越来越大。碳靶电流为1 A时,镀层的截面形貌为细晶团簇结构;碳靶电流为3 A时,镀层截面产生柱状结构。镀层的复合硬度随着镀层碳靶电流的增加逐渐增大,在碳靶电流为3 A时,镀层的维氏硬度最大,为436HV。随着碳靶电流增加,镀层电导率逐渐上升。结论随着碳靶电流的增大,镀层致密度逐渐下降,镀层的电导率逐渐增加,镀层的摩擦系数逐渐减小,适当的碳靶电流能使类石墨镀层在功能化与力学性能上达到最佳效果。     

铁含量对钒钛铁精矿原位合成铁基摩擦材料的影响

以钒钛铁精矿和石墨为原料,在真空条件下采用原位碳热反应加烧结工艺制备了铁基摩擦材料,研究了铁含量(66wt%~82wt%)对铁基摩擦材料微观组织、相对密度、硬度、摩擦系数、磨损率、导热系数和压缩强度等性能的影响。结果表明:利用钒钛铁精矿可制备出性能良好的铁基摩擦材料。随铁含量增加,材料孔隙率逐渐减小,材料微观组织里出现层片状珠光体的趋势先增强后减弱。材料相对密度、布氏硬度、导热系数和压缩强度均随铁含量的增加而增大,但对磨损率而言,当铁含量从66wt%增加到78wt%时,磨损率从2.27×10~(-7)cm~3/J逐渐增大到3.82×10~(-7 )cm~3/J。当铁含量再增大到82wt%时,磨损率反而快速降低至1.06×10~(-7)cm~3/J。综合来看,当铁含量在70wt%~74wt%内时制备的铁基摩擦材料有较适中的摩擦系数、磨损率和导热系数。     

The conversion of chromium oxide to chromium carbide

The thermodynamic equilibria between chromium oxide, chromium carbide, and a CO-CO₂ mixture was calculated for various conditions. Experimental results on the rate of the Cr₂O₃ conversion to chromium carbide in CO-CO₂ mixtures at 1200°C are reported. The conversion rate was low and was strongly dependent on the carbon activity.     

Process of pulse electrodeposition nanocrystalline chromium from trivalent chromium bath

Nanocrystalline chromium coating was prepared by pulse electrodeposition from trivalent chromium bath containing carboxylate-urea as complexing agent. The effects of electrodeposition parameters such as current density, bath temperature and solution concentration on the thickness and electrodeposition velocity of Cr deposited films were investigated. The crystallographic structures, morphology and chemical composition of Cr deposited films were analyzed by means of XRD, SEM and EDS. The results indicate that the deposited films with thickness up to 11.2 μm possess a smooth and clean appearance, and the grain size is less than 100 nm. The coating is pure chromium and the Cr deposit has face-centered cubic （fcc） structure and exhibits a （210） growth preference. Both the electrodeposition velocity and thickness exist maximum under different concentration complex agents, ureas, acetates, different temperatures and current densities. Compared with direct current electrodeposition, the thicker coating and finer grains can be obtained at lower temperature and current density by pulse electrodeposition. The electrodepostion velocity is about 0.24 μm/min, which is faster than that by direct current electrodeposition. In l mol/L H2SO4, 3.5% NaCl and 10% NaOH solution, corrosion potential of Cr pulse-deposited film is about 100 mV higher than that of direct current. Corrosion and passivation current densities are lower and the nanocrystalline exhibits better corrosion resistance.     

Synthesis of chromium carbide by reduction of chromium oxide with methane

In the present work, production of the chromium carbide was investigated by reduction of chromium oxide with methane-containing gas mixture. The experiments were conducted on the chromium oxide powder and methane gas at different temperatures, times, and gas mixtures. X-ray diffraction (XRD) analysis was used to characterize the products at different stages of reduction. The morphology of the starting chromium oxide powder and Cr₃C₂ were studied by electron microscopy technique. The results showed that the minimum temperature and time for carbide formation in 30%-methane gas mixture is about 850 °C and 20 min, respectively. X-ray diffraction analysis showed that Cr₃C₂ is the only carbide product. The formation of chromium carbide in 30%-methane gas mixture was completed at 1000 °C and 60 min.     

Effect of chromium content and heat treatment on creep of chromium bronze

Conclusions At testing temperatures below 0.5T_m the structure of the alloy affects the creep resistance in the same way as during tensile strength tests. The more dispersed (but less stable) structure ensures higher strength and a lower steady creep rate.At temperatures above 0.5T_m the less dispersed (but more stable) structure of the bronze is responsible for the lower creep rate.State Scientific-Research and Design Institute of Alloys and Treatment of Nonferrous Metals. Translated from Metallovedenie i Termicheskaya Obtabotka Metallov, No. 11, pp. 61–63, November, 1982.     

Electrodeposition of chromium from trivalent chromium urea bath containing sulfate and chloride

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