基于原位摩擦化学处理技术改善金属材料的摩擦学性能

针对摩擦磨损引起的材料失效和机械设备损坏状况,基于原位摩擦化学处理技术研制了一种抗磨、减摩和润滑性能优异的摩擦处理剂.采用四球式摩擦磨损试验机和球-盘式高温摩擦磨损试验机设计了摩擦化学处理试验,通过改变加载负荷、温度、摩擦副材质和摩擦副之间的接触形式等试验参数考察了摩擦处理剂的抗磨减摩性能,采用SEM、EDS和XPS分析了摩擦处理剂的摩擦化学作用机理.结果表明在摩擦过程中,摩擦处理剂在金属表面原位形成了含MoS2、FeS和FePO4等减摩润滑效果良好的摩擦化学反应膜,从而显著的改善了金属材料的摩擦学性能,其抗磨性能和减摩性能分别较普通油提高了38%和46%.     

45钢表面原位摩擦化学反应膜形成过程及力学性能

制备了一种用于原位摩擦化学处理技术的天然矿物微粉摩擦处理剂.采用环-块摩擦磨损试验机对其在柴油机油中的添加量进行了优化,研究了其在45钢表面的原位摩擦化学反应膜的形成过程及力学性能,探讨了形成机理.结果表明:处理剂含量为0.5 wt%时对45钢表面具有较好的优化效果,其摩擦因数和质量磨损率分别较基础油降低约19.7%和71.8%.摩擦处理表面较为光滑平整,形成了由铁的氧化物、铁镁硅酸盐及含碳化合物构成的摩擦化学反应膜,且随着时间的增加逐步由疏松多孔趋于致密连续,具有较高的力学性能,显著提高了45钢的表面强度及磨损抗力.     

含合成蛇纹石纳米管润滑油对镁合金摩擦学性能的影响EI北大核心CSCD

采用水热合成法制备具有蛇纹石结构的纳米管状羟基硅酸镁粉体,利用SRV磨损试验机考察纳米管状羟基硅酸镁粉体作为润滑油添加剂对镁合金/GCr15钢摩擦副摩擦磨损性能的影响,利用扫描电镜、X射线能谱仪、X射线光电子能谱仪、透射电镜、纳米压痕仪等表征分析镁合金磨损表面,探讨蛇纹石纳米管对镁合金的减摩自修复机理。结果表明:蛇纹石纳米管能够显著降低镁合金的摩擦因数和磨损体积,当蛇纹石添加量为0.3%、载荷为20 N、频率为20 Hz时,摩擦因数和磨损体积与基础油润滑下相比降幅最大,分别为64.07%和61.58%。摩擦过程中蛇纹石与摩擦副表面发生摩擦化学反应,在镁合金表面生成了由SiO_(2)、(Mg/Fe)_(2)SiO_(4)、MgSiO_(3)等硬质陶瓷颗粒和MgO、Fe_(2)O_(3)等金属氧化物以及石墨、ZnS、蛇纹石纳米管等组成的非晶/纳米晶结构自修复膜,自修复膜优异的力学性能显著改善了镁合金的摩擦学性能。     

纳米羟基硅酸镁的原位表面修饰和二次表面修饰

对纳米羟基硅酸镁粉体分别采用原位表面修饰和二次表面修饰进行表面化学修饰,在其表面引入众多有机短链和有机长链,使纳米羟基硅酸镁粉体在有机介质中有较好的相容性和分散稳定性。利用透射电子显微镜和傅立叶红外光谱仪分别表征了表面修饰改性前后纳米粉体的表面形貌和红外吸收光谱。结果表明:修饰剂与粉体表面发生化学吸附。未经表面修饰处理的纳米粉体呈纳米颗粒和纳米管/棒的团聚体;经过原位表面修饰处理的纳米粉体的分散性得到很大改善,呈局部分散的表面形貌;经过原位表面修饰和二次表面修饰,纳米羟基硅酸镁粉体在有机溶剂中得到有效分散。     

铝合金表面蛇纹石复合微弧氧化膜层的制备及摩擦学性能北大核心CSCD

采用微弧氧化技术,在电解质溶液中添加蛇纹石微纳米颗粒,在ZL109铝合金表面原位生长陶瓷层。对未添加和添加蛇纹石微纳米颗粒制得的微弧氧化陶瓷膜层进行扫描电镜(SEM)、能谱(EDS)及X射线衍射(XRD)分析,并与铸铁试样进行摩擦磨损试验,探究蛇纹石微纳米颗粒对铝合金微弧氧化陶瓷膜层成分及摩擦学性能的影响。结果表明:在电解液中添加蛇纹石微纳米颗粒改变了微弧氧化陶瓷膜层的元素组成和相成分,在摩擦磨损试验中,微弧氧化膜层中的蛇纹石在摩擦能的作用下诱发了铸铁销表面的内氧化反应,在摩擦接触微区形成了Mg Si O3、Fe2O3及Fe3O4复合陶瓷表面自修复层,提高了铸铁销表面显微硬度,降低了摩擦磨损过程中的摩擦系数和铸铁销的磨损率。     

激光诱导表面改性制备铜基非晶-纳米晶粉末冶金摩擦材料

为改善铜基粉末冶金摩擦材料的摩擦磨损性能,研究了激光诱导表面改性制备铜基非晶-纳米晶粉末冶金摩擦材料方法.采用扫描电镜、透射电镜、X射线衍射仪及硬度计等对粉末冶金摩擦材料层微观组织及性能进行了表征,结果表明:由于激光的急速加热和冷却以及以小质点杂质形式分布于α-Cu基体中的Zn,Sn和Pb元素抑制了再结晶的形核及长大,导致铜基非晶一纳米晶粉末冶金摩擦材料的形成.同时激光表面改性处理后,α-Cu相的晶粒尺寸减小了35%,二类应变均方根值增大39%,位错密度增加97%.聚合生长状态的α-Cu产生边缘溶解,大体积α-Cu枝解细小化.摩擦材料表观硬度提高了12.7%,α-Cu相显微硬度提高了14%.耐磨性能提高45%,摩擦系数升高1%.     

化学织构化45#钢表面涂覆MoS2薄膜的摩擦学性能

目的提高干摩擦条件下45~#钢表面的减摩耐磨性能。方法采用FeCl_3与HCl混合刻蚀液对45~#钢表面进行化学织构化处理,并在织构表面涂覆MoS_2形成复合润滑薄膜。通过摩擦磨损实验,评价了表面织构以及复合润滑薄膜的减摩耐磨特性,并通过扫描电子显微镜对磨痕进行分析。结果进行化学织构化处理后,45~#钢表面形成了均匀的微坑结构及由点蚀产生的孔洞结构,表面粗糙度Ra上升到了0.89μm,与未刻蚀的样品相比,刻蚀后表面的摩擦系数降低了23%,其摩擦过程也更稳定。这可能是由于刻蚀后产生的微坑与点蚀孔洞结构能够捕获磨屑,减少磨粒磨损。在经化学刻蚀后的织构表面上构筑了MoS_2薄膜,与未刻蚀的样品相比,这种表面的摩擦系数得到了极大的降低,能达到0.1左右,其耐磨寿命也得到了极大的延长,磨痕宽度也有了明显的降低。其主要原因可能是由于刻蚀后产生的微坑与点蚀孔洞结构存储的固体润滑剂,在摩擦过程中由对偶件带入摩擦区域进行了有效润滑。结论化学刻蚀形成的表面织构能够在一定程度上提高45#钢表面的摩擦学性能,涂覆MoS_2形成的复合润滑膜能够极大地降低45#钢表面的摩擦系数并大大延长其耐磨寿命。     

Si对原位自生镁基复合材料摩擦磨损性能的影响

采用原位法制备Mg2Si/AM60复合材料,研究了不同质量分数的Si粉对Mg2Si/AM60复合材料摩擦磨损性能的影响。结果表明,Si质量分数增加,复合材料硬度增加,其磨损量随之减小,磨损性能得到显著加强。外加载荷增大,复合材料磨损量持续增加。与基体AM60相比,Mg2Si/AM60复合材料有效推迟微量磨损向严重磨损转变的时间。     

表面修饰纳米铜颗粒的制备及摩擦学性能研究

采用乳液法在水-甲苯体系中原位合成了含硫、氮有机物修饰的铜纳米微粒,用透射电镜(TEM),红外光谱(FTIR)表征了纳米颗粒的尺寸、形貌和结构,在四球摩擦磨损试验机上考察了纳米铜添加剂在石蜡基础油中的抗磨减磨性能,最后分别采用扫描电子显微镜(SEM)和X光电子能谱仪(XPS)分析了磨斑的表面形貌及其化学组成.结果表明:铜纳米微粒添加剂能够显著提高基础油的极压性能,同时具有良好的抗磨性能;发现在摩擦过程中铜纳米微粒在表面形成沉积膜,这种沉积膜与表面修饰层形成的摩擦化学反应膜产生协同作用,从而表现出优良的极压抗磨性.     

Si对原位自生Mg2Si/AM60复合材料组织及性能的影响

采用原位合成技术制备Mg2Si/AM60复合材料,研究不同Si含量对其组织及性能的影响.结果表明:镁合金中加入结晶Si后,出现短棒状及中国汉字状的Mg2Si相;当Si含量较高时,中国汉字状的Mg2Si相消失,变成不规则的块状.制备过程中对复合材料进行机械搅拌,Mg2Si相的分布较未搅拌更加均匀、弥散.复合材料的抗拉强度、硬度随Si含量的增加呈上升趋势,延伸率则下降.当Si量为1.0%(质量分数,下同)时,强度较基体提高12%,含量为5%时,硬度较基体提高48.6%.     

On The Enhancement of Wear Resistance of Hardened Carbon Tool Steel （AISI 1095） With Cryogenic Quenching

Many experimental investigations reveal that it is very difficult to have a completely martensitic structure by any hardening process. Some amount of austenite is generally present in the hardened steel. This austenite existing along with martensite is normally referred as the retained austenite. The presence of retained austenite greatly reduces the mechanical properties and such steels do not develop maximum hardness even after cooling at rates higher than the critical cooling rates.Strength can be improved in hardened steels containing retained austenite by a process known as cryogenic quenching.Untransformed austenite is converted into martensite by this treatment. This conversion of retained austenite into martensite results in increased hardness, wear resistance and dimensional stability of steel. Wear can be defined as the progressive loss of materials from the operating surface of a body occurring as a result of relative motion at the surface. Hardness, load,speed, surface roughness, temperature are the major factors which influences wear. Many studies on wear indicate that increasing hardness decreases the wear of a material. With this in mind, to study the surface wear on a surface modified (Cryogenic treated) steel material an attempt has been made in this paper. In this study as a Part -I Hardening was carried out on carbon tool steel (AISI 1095) of different L/D ratio with conventional quenchants like purified water, aqueous solution and Hot mineral oil. As a Part -II hardening was followed by quenching was carried out as said in Part- I and the hardened specimen were quenched in liquid Nitrogen which is at sub zero condition. The specimens were tested for its microstructure, hardness and wear loss. The results were compared and analyzed. The alloying elements increases the content of retained austenite hence the material used was AISI 1095 (Carbon 0.9%, Si 0.2%, Mn0.4% and the rest Iron)     

喷涂工艺对超音速火焰喷涂Al-Cu-Fe-Si准晶合金涂层性能的影响

目的使用活性燃烧高速燃气喷涂(AC-HVAF)方法制备高质量的Al-Cu-Fe-Si准晶涂层,研究喷涂工艺对涂层性能的影响。方法采用气雾化Al-Cu-Fe-Si准晶合金粉末,利用AK02T型AC-HVAF喷涂系统制备Al-Cu-Fe-Si准晶涂层材料。通过X射线衍射及扫描电镜观察分析准晶合金粉末和涂层的组织与结构,通过电化学工作站、显微硬度计和接触角测试仪等手段分析准晶合金涂层的耐蚀性、显微硬度及抗粘性能。结果对气雾化准晶Al-Cu-Fe-Si合金粉末的研究发现,冷却速率显著影响准晶合金粉末的组织,在冷却速率较快的粉末中形成胞状晶组织,准晶I相含量较高。对准晶合金涂层进行热处理,高温退火显著提高了涂层的硬度,950℃退火12 h后,硬度值达到(724±153)HV0.1。分别对准晶合金涂层和基体45~#钢的接触角进行测量,准晶合金涂层的接触角最大为95°,而45~#钢的仅为79°。通过电化学工作站测试比较涂层的耐蚀性,发现在3.5%(质量分数)的Na Cl溶液中,喷涂在45~#钢和5052铝合金基体上的涂层腐蚀电流密度J_(corr)分别为6.8×10~(-6),2.0×10~(-7)A/cm~2。结论不同粒径的气雾化准晶合金粉末的相组成不同,选择合适的粒径是保证铝基准晶合金涂层质量的前提。对涂层进行合适的热处理可以有效地提高涂层的显微硬度,铝基准晶合金涂层的接触角较45~#钢的高,提高了基体的抗粘性。不同基体上制备的准晶合金涂层的耐蚀性有很大差异,5052铝合金基体上的准晶涂层耐蚀性优于喷涂在45~#钢基体上的涂层。     

Mechanisms governing tribochemical reduction of metals and non-metals from their oxides

The paper describes the physical and chemical mechanisms governing the tribochemical reduction of metals and non-metals from their oxides. The reduction was started by a tribochemical activation of initial constituents in a vibrating mill used as a reactor. Powders of oxides of copper, iron, molybdenum, tungsten, vanadium, titanium and boron and also such chemically pure metals as magnesium, aluminium and titanium were used as reaction constituents. The triboactivation energy contribution needed to start the explosive mechanism reduction is found to increase as the heat of reaction decreases and the heat of formation of the associated product rises. Introducing oxygen into the reactor during the tribochemical activation of powders of oxides together with magnesium causes the intense oxidation of magnesium and stimulates the reduction process. To increase the yield of tungsten monocarbide from tungsten concentrate, the reduction process should be implemented in an atmosphere of hydrogen or hydrocarbons.     

Lubricity of volatile lubricants in sheet metal rolling

A series of experiments is carried out by using a rolling type tribometer to investigate the lubricity of the volatile lubricants at high speed forming. The roll material is the die steel alloy SKD11, and the workpiece material is the mild steel SPCE with a rough surface and the aluminum alloy A3004 with a smooth surface. Experimental results show that the friction coefficient decreases with increasing working velocity for both SPCE and A3004, in any lubricant. With an increase of reduction in thickness, the friction coefficient decreases for SPCE, but increases for A3004. Some volatile lubricants have the same lubricity as the generally used mineral oil with low-viscosity by judging from the value of friction coefficient, the surface appearance of rolled workpiece and the roll surface damage.     

SiC表面合金化ZG45钢的组织观察

以SiC粉末为主要原料制成涂料涂覆在EPS泡沫塑料模样的表面上.采用EPC真空消失模铸造方法浇注ZG45钢液,从而制备出SiC表面合金化ZG45钢基材料.采用光学显微镜、扫描电镜 (SEM) 和EDS观察和分析了材料的显微组织.结果表明:材料由表及里明显地由3个区域组成,即:表面合金化层、中间过渡层和内部基体层.在表面合金化层中,SiC颗粒已全部发生分解,组织由片状石墨+碳化物+富Si铁素体+珠光体组成;过渡层组织在靠近表面合金化层时全部由珠光体组成,而在靠近基体区域时组织由铁素体+珠光体组成,并且可以观察到部分晶粒中有少量的碳化物和富Si铁素体存在;基体由铁素体+珠光体组成.     

Microstructure and corrosion resistance of Ti-Ni/steel composite materials

Ti-Ni composite sub-micron powders with different compositions were prepared by vacuum melting and atomization technology. These powders, after being mixed with a solution of phenolic resin and alcohol, were applied on the mold cavity wall, by which a casting-infiltration layer was introduced on the surface of ZG45 steel via reactions between the powders and molten steel under the heat released by solidification. The effects of the powders’ composition and pouring temperature on the corrosion resistance of the casting-infiltration layer were studied. An optimal casting-infiltration layer with a thickness of ∼7 mm was obtained by infiltrating the Ti-Ni composite powders containing 35wt.% Ti to ZG45 steel pouring at 1,650 °C. The casting-infiltration layer has a good metallurgic bonding with the matrix, and is mainly composed of Fe₂Ti phase and continuous γ-(Fe, Ni) solid solution. In the corrosive H₂SO₄ solution, the corrosion potential of the casting-infiltration layer is lower than the matrix, tending to form a passivation film, which lowers the dissolution rate especially when the potential rises to 0.50 V. After dipping in the 10wt.% NaCl solution for 480 h, a lot of corrosion holes appear in the ZG45 steel matrix, while there are no obvious traces of corrosion on the casting-infiltration layer.

     

Niobium Powders of Mesoporous Structure

The mesoporous structure of niobium powders of specific surface areas from 32 to 150 m²/g obtained through reduction of niobium-oxide compounds by magnesium vapors has been investigated. A doubling of the specific surface area of magnesium-thermic niobium powders in comparison to tantalum powders has been shown to be caused by the larger volume and smaller size of pores. For a powder with a specific surface area of 150 m²/g, 90% of the surface is governed by pores of sizes smaller than 5 nm. Although the X-ray pattern of the powder corresponds to the metal niobium, 96.5% of this powder weight consists of a natural surface-oxide film, according to the TGA data. The thickness of this oxide decreases in comparison with the surface oxide on the compact metal depending on the powder mesoporous structure.     

Einfluß der Luftfeuchtigkeit auf den Gleitverschleiß metallischer Werkstoffe

Influence of atmospheric moisture on gliding wear of metallic materials A study on gliding wear has been undertaken using a Siebel-Kehl machine and – without lubrication – iron and steels (couples of identical materials), brass (Ms 58) and cast bronze (G Sn Bz 10), coupled with steel C 45, in air of different humidities and water vapour concentrations, and under vacuum. With these conditions, tribochemical reactions and the metal oxide layers formed thereby in the gliding surface, as well as their adhesion, play a vital part. In the range of severe wear the wear-preventing oxide formation is enhanced by dry air, while it does not come to bear generally in moist air, although there may be a transition to an oxidic mechanism even there. Experiments made in water vapour atmosphere and under vacuum have confirmed this fact. The effect of the formation of oxide and protective layers is considerable in the case of the ferrous metals, in particular soft iron, quite in contrast to the conditions prevailing with bronze and brass. The influence of the humidity of the act in the mild wear range is inverse to that in the severe wear range. The action of water vapour on the boundary faces is greatly exeeded by the influence of the tribochemical reactions, at least with the ferrous materials.     

采用表面处理工艺解决CA6140车床方刀架故障

传统车床方刀架在使用中经常出现偏移现象,存在小滑板上销孔套筒磨损过大的问题,影响了加工精度,降低了工作效率。以CA6140车床为例,经研究分析,其销孔套筒的材料为45号钢,按传统热处理方式对其进行处理后耐磨度不够。探讨了采用现代表面处理工艺强化45号钢耐磨性能的可行性,并对实际生产中车床方刀架的故障进行了处理。