Dry Friction and Wear Characteristics of Rare-Earth/MoSi_2 Composite

MolybdenumDisilicide (MoSi2 )intermetallicspossessesmetallic likeandceramic likeproperties .Studyonitsfrictionandwearcharacteristicshasim portanttheoreticalandpracticalsignificance[1～ 5] .ItisusefultoreinforcetheMoSi2 materialbyusingthesec ondphaseforimprovementofthefrictionandwearcharacteristics[3 ,6] .Hawketal.[3 ] comparedthewearresistanceofMoSi2 withthatofMoSi2 Nbcomposites ,Nb ,aluminides (Fe3 Al,TiAl)andoxidationceramics(Al2 O3 andPS ZrO2 ) ,andfoundthatthewearresis tanceofMoS…     

油润滑下Al/MoSi2材料的摩擦学特性

运用M-200型磨损试验机测定了油润滑下Al/MoSi2材料的摩擦磨损性能，采用SEM和X射线观察与分析了摩擦副表面的形貌和相组成，探讨了磨损机制。结果表明：采用20#机油润滑可有效地提高Al/MoSi2材料的摩察磨损综合性能；与干摩擦状态相比，其摩擦系统和磨损率分别下降了40%和60%；油润滑时，Al/MoSi2材料的磨损机制主要表现为疲劳点蚀和磨粒磨损。     

多层石墨烯和Fe_2O_3纳米颗粒对TC11合金磨损行为的影响

通过在TC11合金摩擦界面添加机械混合的多层石墨烯和Fe_2O_3纳米颗粒,研究其对TC11合金磨损行为的影响,并与未添加及只添加多层石墨烯或Fe_2O_3纳米颗粒时进行对比。利用XRD、SEM和EDS等微观分析手段对磨损表面的物相、形貌和成分进行检测分析,并探讨摩擦层的形成过程及纳米材料的作用。结果表明:添加多层石墨烯或Fe_2O_3纳米颗粒时形成的摩擦层不能稳定存在,无法改善TC11合金较差的耐磨性。而添加机械混合的多层石墨烯和Fe_2O_3纳米颗粒时,在磨面形成同时具有良好润滑性和优异承载能力的双层摩擦层,能有效地阻止金属间相互接触,对基体起到保护作用,使得TC11合金的磨损量显著下降。     

Si和La元素对Mo丝显微组织与力学性能的影响

系统研究了La、Si单元掺杂和复合掺杂对钼丝的显微组织和力学性能的影响及其作用机制,优化出具有优异力学性能的Mo-Si-La合金丝的成分为Mo-0.15Si-(0.5～0.8)La.MoSi2与Mo原位反应生成Mo5Si3和Mo3 Si硬质相,起到良好的晶粒细化作用和弥散强化作用.La2O3颗粒通过延迟微裂纹的形成和扩...     

等离子喷涂Al_2O_3-TiO_2陶瓷涂层的显微组织及摩擦学性能

以Al_2O_3-TiO_2(x=0%,3%,13%,20%,40%,质量分数)复合陶瓷粉末为原料,采用等离子喷涂工艺在316L不锈钢基体表面制备5种陶瓷涂层。利用扫描电镜(SEM)、能谱仪(EDS)和X线衍射仪(XRD)、荧光金相显微镜分析粉末和涂层形貌、微观结构、物相组成及涂层孔隙率;利用显微硬度计及摩擦磨损试验机测试涂层力学及摩擦学性能,观察试样磨损形貌,分析磨损机理。结果表明:涂层呈典型的等离子喷涂层状堆积特征,涂层与基体结合良好。随TiO_2含量增加,涂层主相由γ-Al_2O_3向Al_2TiO_5相过渡,涂层韧性升高,硬度和孔隙率降低。在大气环境下,低TiO_2含量的涂层(Al_2O_3、AT3)发生应力疲劳磨损,高TiO_2含量的涂层(AT13、AT20和AT40)发生应变疲劳磨损;而在水环境下,5种涂层均发生应力疲劳磨损。     

添加La_2O_3对尼龙1010复合材料的硬度和摩擦磨损性能的影响

采用热挤压方法制备了含不同 L a2 O3添加量的尼龙 10 10 (PA10 10 )复合材料。测定了复合材料的密度和硬度。在 MM- 2 0 0型环 -块实验机上考察了复合材料分别与黄铜和 45 #钢配摩的摩擦磨损性能。研究结果发现 ,填充 15 % (质量分数 ) L a2 O3的 PA10 10复合材料硬度最高 ;摩擦学性能显著改善。摩擦系数降低为原来未填充L a2 O3的 PA10 10的一半 ,磨损体积降低 1个数量级左右。 PA10 10复合材料与 45 #钢配摩的摩擦系数和磨损量均低于和黄铜配摩 ,这是其与钢配摩比与黄铜配摩的转移膜更加均匀、致密的结果     

Effect of La_2O_3 on microstructure and high-temperature wear property of hot-press sintering FeAl intermetallic compound

FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders.Effect of La2O3 on microstructure and high-temperature wear property of the sintered FeAl samples was investigated in this paper.The results showed that 1 wt.% La2O3 addition could refine the microstructure and increase the density of the FeAl intermetallic compound,and correspondingly improved the high-temperature wear resistance.SEM and EDS analyses of the wo...     

干摩擦条件下SiC/MoSi_2与WC-Co对磨时的磨损特性研究

采用扫描电镜和能谱仪观察和测定了SiC/MoSi2复合材料与WC-Co对磨试样的磨损表面和磨屑的形貌及成分,研究了SiC/MoSi2复合材料与WC-Co摩擦副的干摩擦磨损性能和磨损机理。研究结果表明:SiC/MoSi2复合材料与WC-Co摩擦副的主要磨损机制在初始磨损阶段主要由微观断裂机制控制,并伴有粘着磨损、磨粒磨损和氧化磨损;在稳定磨损阶段由粘着磨损机制控制,并伴有微观断裂和氧化磨损。SiC/MoSi2复合材料与硬度较大的WC-Co磨轮对磨时的磨损率比与硬度较小的CrWMn钢磨轮对磨时的磨损率低。     

Tribological properties of Cu-La_2O_3 composite under different electrical currents

A new type of Cu-La2O3 composite was fabricated by internal oxidation method using powder metallurgy.Sliding wear behavior of the Cu-La2O3 composite was studied on a pin-on-disc wear tester under various electrical currents and applied loads.The worn surfaces were characterized using scanning electron microscopy and energy dispersive spectroscopy to probe the wear mechanisms.The results indicated that applied load had a significant effect on the wear rate of the Cu-La2O3 composite pins.The wear rate displayed the minimum value at the load of 50 N during electrical sliding processes.The corresponding wear mechanism was identified to be adhesive wear,abrasive wear,oxidation wear and arc erosion.     

Influence of La2O3 addition on microstructure and wear resistance of Fe-Cr-C cladding formed by arc surface welding

The Fe-Cr-C claddings formed by arc surface welding with different La2O3 additions were investigated. The microstructures were observed by optical microscopy (OM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The phase structures were measured by X-ray diffraction (XRD). The wear resistances of the claddings were tested by friction and wear experiment. On this basis, the carbide refinement mechanism by inclusion enriched with La was discussed theoretically. The results showed that, the microstructure of the Fe-Cr-C cladding consisted of primary (Cr,Fe)7C3 carbides and eutectic (γ-Fe+(Cr,Fe)7C3 ) structure. With La2O3 addition increasing, the primary carbides were refined, and the mass loss of the cladding decreased gradually. The Fe-Cr-C cladding with 4wt.% La2O3 addition had a best wear resistance behaviour. The RE inclusion LaAlO3 as heterogeneous nuclei of the primary M7C3 was medium effective, and could refine the M7C3 carbides. Besides, the wear resistance could be improved by adding La2O3 in the claddings.     

Effect of artificial tribological layer on sliding wear behavior of H13 steel

An artificial tribological layer was formed on the worn surface during sliding, through supplying MoS2 , Fe2 O 3 or their equiponderant mixtures onto the sliding interface of H13/GCr15 steels.The effect of this tribological layer on the wear behavior of H13 steel was studied.The worn surfaces and subsurfaces of H13 steel were thoroughly characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS); the wear mechanisms were explored.The research results demonstrated that tribological layer did not exist during sliding of H13 steel with no additive, but it formed with the addition of MoS2 , Fe2 O 3 or their equiponderant mix-tures.When there was no tribological layer, the wear rate rapidly increased with an increase of the load.In this case, adhesive and abrasive wear prevailed.As the additives were supplied, the artificial tribological layer was observed to be immediately formed and stably existed on worn surfaces.This tribological layer presented an obvious protective function from wear and friction.Hence, the wear rate and friction coefficient were significantly decreased.MoS2 as tribological layer seemed to present more obvious protective function than Fe2 O 3 .By supplying their mixture, the artificial tribological layer possessed not only the load-carrying capacity of Fe2 O 3 , but also the lubricative capacity of MoS2 .These two simultaneous capacities could improve the friction and wear properties of H13 steel further.     

Catalytic Reduction of SO2 on CeO2-La2O3 Rare Earth Mixed Compounds

Adding rare earth oxide CeO2 with variable valences to La2O3 formed a mixture of rare earth oxides. By means of dipping CeO2, La2O3 and their mixture, whose carriers were all γ-Al2O3, were used as the catalyst for the reduction of SO2 by CO. The activation process of this catalyst and the impact of temperature and reactant concentration on the activation process were investigated. Using X-ray diffraction, the structure characteristics of catalyst before and after reaction were analyzed to reveal the change of phase structure. The result shows that the rare earth oxide mixtures composing of CeO2 and La2O3, as the catalyst for the reduction of SO2 by CO, diminish activation temperature 50～100℃ less and have higher activity than a single oxide CeO2 or La2O3. The reason possibl is that La2O3 goes into in the lattice of CeO2 to form solid phase complex CeO2-La2O3 and increases the capability of CeO2-La2O3/γ-Al2O3 catalyst to store oxygen, which supplies the redox of CeO2 reaction with a better condition. At the same time, elemental sulfur formed in the redox reaction impels La203 to be transformed to activation phase La2O2S in a lower temperature, which can be explained with the synergism between redox reaction and COS intermediate mechanism reaction.     

Effect of Volume Fraction of Particle on Wear Resistance of Al2O3／Steel Composites at Elevated Temperature

Inpreviouswork,heat resistingsteelwithlow carboncontentandhighoxidationresistanceatele vatedtemperaturewastakenasthematrixmaterial. AndAl2O3ceramicparticleswereutilizedasrein forcedphasefortheirgreatstabilityandhighrigidi tyatelevatedtemperature.Inorde…     

����������La2O3-Al2O3-CaF2����������Ũ��ģ��

In order to accurately control the rare earth content in liquid steel in electroslag remelting (ESR) process, according to the ion and molecule coexistence theory (IMCT) of slag structure and corresponding phase diagrams, a thermodynamic calculating model for the evaluation of mass action concentrations (designated by Ni for structure unit i) for La2O3-Al2O3-CaF2 slag system was formulated. The results show that the calculated values of NLa2O3 are in good agreement with the reported measured values, indicating that this calculating model can wholly embody the characteristics of the slag system. The activity of La2O3 decreases with the increasing of the Al2O3 and CaF2 content, and Al2O3 is stronger than CaF2 in decreasing the activity of La2O3. But the activity of La2O3 increase with the increasing in temperature at the composition range of 30% La2O3, 20% Al2O3, 50% CaF2. Above all, the activity of La2O3 in La2O3-Al2O3-CaF2 slag system can be quantitatively analyzed by this thermodynamic model, and this model can provide a theoretical basis for precisely controlling the lanthanum content in molten steel in ESR process.     

Effect of Microstructures on Resistance of a Hot Elevated-Temperature Wear Working Die Steel

 Elevated-temperature wear tests under atmospheric conditions at 400 ℃ were performed for a hot working die steel H21 on a pin-on-disk wear tester. The phase and morphology of worn surfaces were examined using XRD and SEM, and the relation of wear resistance to tempered microstructures was studied for H21 steel. XRD patterns exhibit that oxidative wear is a predominated wear mechanism with Fe3O4 and Fe2O3 on worn surfaces. It is found that with increasing normal load, obvious plastic deformation of substrate appears on worn surfaces. Microstructures start to affect apparently wear resistance of the steel with an increase of load. Under loads of 50-100 N, wear losses of steel retain low values and relatively approach for steels with various microstructures. As loads are increased to 150-200 N, wear losses of steel start to increase obviously and present apparent difference for steel with various microstructures. Wear resistance is found to increase in the sequence as follows: tempered sorbite, tempered martensite, tempered troostite without secondary hardening and tempered troostite with secondary hardening or upcoming one. Higher strength and microstructural stability are required for steels with excellent wear resistance.     

3Cr2W8V钢高温高载下的干摩擦滑动磨损特性

对３Ｃｒ２Ｗ８Ｖ钢高温高载下的干摩擦滑动磨擦滑动磨损性及磨损面形貌、磨损面表层和次表层的组织和硬度进行了试验和分析。结果表明：高载下３Ｃｒ２Ｗ８Ｖ钢的力学性能是决定材料磨损特性的低载下磨损面上形成氧化物磨屑的覆盖,而在国高载和高温下都未形成氧化物磨屑的覆盖;高温高载下,主要因３Ｃｒ２Ｗ８Ｖ钢本身承能力下降,氧化物磨屑未能覆盖于磨损面上,故对磨损面起不到保护作用。     

Al_2O_3La_2O_3Y_2O_3/Cu复合材料的电弧侵蚀特性研究

采用喷射沉积和内氧化法制备出Al2O3La2O3Y2O3/Cu复合材料,研究该材料在直流20 V/20 A的工作条件下触点的电弧侵蚀特性,并与Al2O3/Cu材料进行了对比分析.利用电子天平、扫描电镜等方法分析电弧侵蚀后触点的质量变化和表面微观结构.结果表明,通过添加Y2O3、La2O3稀土氧化物颗粒,可有效降低触头材料的材料转移量.Al2O3La2O3Y2O3/Cu材料的抗熔焊性和抗烧损性优于Al2O3/Cu材料的性能.在直流阻性负载条件下Al2O3La2O3Y2O3/Cu阳极触头表面形成凹坑,阴极触头表面形成凸起,触点表面显示出浆糊状凝固物和喷发坑等电弧侵蚀形貌特征.     

La_2O_3掺杂对V_2O_5-WO_3/TiO_2催化剂SCR性能的影响

通过共沉淀法将La组分掺入到TiO_2载体中,采用浸渍法将V和W组分负载到La_2O_3-TiO_2复合氧化物上,制备出V2O5-WO3/La_2O_3-TiO_2催化剂。考察不同La_2O_3掺杂量对其NH3催化还原NO性能的影响,同时通过多种物理化学手段进行表征分析。XRD,NH_3-in situ DRIFTS,H_2-TPR,XPS和UV-vis DRS测试结果表明,元素La与Ti以La-O-Ti键相互作用,生成高度分散的镧物种,也使得TiO_2具有更好的热稳定性,但由于LaO_x物种与VO_x物种和WO_x物种之间的相互作用,降低了催化剂的氧化还原性和表面Brnsted酸数量,从而降低了其催化活性。     

Si_3N_(4(p))/SiC_((w))强韧化MoSi_2基复合材料的显微组织与力学性能

采用热压工艺制备了不同Si3N4(p)和SiC(w)体积含量的MoSi2基复合材料,通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、维氏硬度计、电子万能材料试验机等研究了复合材料的显微组织、硬度、断裂韧度和抗弯强度,并对其强韧化机理进行了初步探讨。结果表明,复合材料结构致密,强化相与MoSi2之间没有新相生成,力学性能较纯MoSi2得到大幅度提高,其中MoSi2-20%Si3N4(p)-20%SiC(w)复合材料具有最好的抗弯强度和断裂韧度,分别为427MPa和10.4MPa.m1/2。复合材料的强化机制为细晶强化和弥散强化,韧化机制为细晶韧化和裂纹偏转与分支韧化。     

Mo-La2O3烧结坯的韧化机制研究

通过扫描电镜，定点探针分析，X射线衍射分析及俄歇电子能谱分析研究了Mo-La2O3烧结坯的韧化机制，结果表明：La2O3的加入提高了烧结钼坯的横向断裂强度和韧性，Mo-La2O3O烧结坯的韧化机制源于间隙杂质在La2O3粒子表面的吸附作用。