B和MoS_2添加量对Ni-Cr合金基材料高温摩擦、磨损行为的影响

本文以Ni-Cr高温合金粉为基,其间添加Mo,B和少量MoS_2。用粉末冶金热压法制备了含不同B和MoS_2添加量的Ni-Cr合金基自润滑材料。借助X射线衍射仪分析了材料结构,用布氏硬度计测试了材料硬度。以研制材料为销样,Al_2O_3陶瓷为盘样,在销-盘式高温摩擦试验机上考察材料在20～700℃温度范围内的摩擦磨损行为。试验结果表明,研制材料主要由Ni基固溶体、Cr_3S_4和MoB 3种相组成。材料硬度随B含量的增加而增加,但高温下其摩擦因数也随之增加。MoS_2添加量为4％(质量分数)的研制材料在20～700℃温度范围内有最佳减摩耐磨综合性能。     

铜银合金线材载流摩擦磨损行为研究

在改造过的MS-T3000摩擦磨损试验机上,以黄铜为摩擦副对热型连铸技术制备的铜银合金线材进行载流摩擦磨损试验,研究了电流对铜银合金导线载流摩擦磨损行为的影响.结果表明,电流强度对铜银合金干摩擦磨损行为有显著影响.电流在0～15 A范围内,随着电流的增加,摩擦系数与磨损率变化基本一致,呈现先减少后增加的趋势.电流较小时,接触电阻也比较小且较稳定;电流高时,接触电阻比较大,波动剧烈,而且有电弧出现.铜银合金导线在带电条件下的主要磨损形式为磨粒磨损、粘着磨损以及以电化学作用为主的氧化磨损或腐蚀磨损.     

W-4.9Ni-2.1Fe 高比重合金的摩擦磨损行为

采用高能球磨和放电等离子体烧结技术制备W-4.9Ni-2.1Fe高比重合金,研究不同球磨时间对合金显微组织结构和摩擦磨损行为的影响. 结果表明:当球磨时间较短（2 h）时,合金粉末中Ni、Fe元素仍以单质的形式存在;随着球磨时间的延长,Ni(Fe)溶入W晶格中形成W的过饱和固溶体,W衍射峰强度逐渐变弱,峰形明显宽化,合金试样的相对密度呈下降趋势;适量的球磨时间（24 h）,既可以保证合金中黏结相的含量和均匀分布,又不至于引入过量的杂质元素而引起合金成分改变,合金拥有最优的耐摩擦磨损性能.      

数值模拟计算在高温合金中的应用

采用热力学动力学和有限元等有关数值模拟方法对高温合金中的若干问题进行了模拟计算,通过计算,给出了高温合金设计、工艺预测及合金发展的理论方向.     

钨铼合金的600℃高温摩擦磨损性能研究

以粉末冶金法制备的W5Re、W25Re合金为研究对象,通过高温摩擦磨损试验,得到材料的高温摩擦磨损性能,利用电子探针、LEICA三维光学显微镜、SEM、EDS等分析手段得到磨损面以及磨损截面的成分、粗糙度、显微组织.结果显示W25Re合金具有优异的耐高温摩擦磨损性能.     

热喷涂Fe基非晶合金涂层的微观结构与摩擦磨损行为

分别采用超音速火焰喷涂工艺和爆炸喷涂工艺,在Q235不锈钢基体上制备Fe基非晶合金涂层,对比研究这2种非晶合金涂层在室温下的干摩擦磨损特性,并探讨摩擦磨损机理.结果表明,与超音速火焰喷涂工艺制备的Fe基非晶合金涂层相比,采用爆炸喷涂工艺制备的涂层更致密,孔隙率为2.1％,显微硬度更高,平均硬度高达1 095.6 HV,且耐磨性更好;并且涂层摩擦因数增至稳定值的时间较短,具有更稳定的摩擦磨损行为.超音速火焰喷涂涂层的磨损形式主要以疲劳磨损为主,而爆炸喷涂涂层的磨损形式为粘着磨损和磨粒磨损的综合作用,并以粘着磨损为主.     

钢中摩擦磨损白层的研究现状

综述了国内外对白层的研究现状,指出了当前白层研究中存在的分歧和争论,分析归纳了表面白层的特征和形成机制,重点讨论了钢轨运行过程中白层的组织结构及形成机制,提出了今后的研究方向.同时用扫描电镜对车轮钢切削白层和钢轨钢中的白层进行观察分析.结果表明,车轮钢切削加工和钢轨运行时,表面组织均发生动态的塑性变形和再结晶,原奥氏体晶粒细化,在随后的冷却的过程中形成马氏体.     

热处理对Fe基非晶合金涂层的相组成及摩擦磨损行为的影响

采用爆炸喷涂技术在Q235不锈钢基体上制备Fe基非晶合金涂层,在500~700℃下对涂层进行热处理,研究热处理温度对涂层的相组成和摩擦磨损性能的影响。结果表明:随热处理温度升高,涂层中非晶相含量明显减少,700℃热处理后,非晶相含量(体积分数)由热处理前的85.54%降至38.94%;热处理后涂层结构变得更致密;喷涂态涂层的平均显微硬度为1 095.6 HV0.05,500℃热处理后硬度变化不大,随热处理温度升高呈缓慢上升的趋势;与喷涂态涂层相比,500和600℃热处理后涂层的平均摩擦因数稍有增加,而700℃热处理后平均摩擦因数减小15%;热处理温度为600℃时涂层的磨损量较热处理前降低20%,耐磨性能最好,而热处理温度为700℃时涂层的质量磨损增大到热处理前的3倍以上,主要是涂层晶化相明显增加,氧化物含量增多,涂层变脆所致;磨损机制为则由喷漆态的粘着磨损向磨粒磨损,再到二者混合机制磨损转变。     

时效处理对粉末高温合金惯性摩擦焊接头室温拉伸行为的影响

对惯性摩擦焊扩散连接的FGH96合金试样经时效处理前后的室温拉伸行为进行了研究,并对其失效机制进行了评估.结果表明,对于焊接态(原状态)FGH96合金试样,由于焊缝区和热影响区的γ'相综合强化效果弱,晶界平直化,导致焊缝区和热影响区的强度低于基体,在室温拉伸过程中塑性应变量大:由于热影响区的晶粒尺寸大,晶界强化效果弱,...     

7075铝合金板材热冲压成形中的高温摩擦

采用自制的板带高温摩擦试验机模拟实际固溶–冲压–淬火一体化热成形工艺下7075铝合金的高温摩擦过程,分别对上下摩擦头进行冷却和加热以模拟实际热冲压过程对模具和压边圈的冷却和加热,分析了下模加热温度、法向载荷和滑动速度对7075铝合金摩擦行为及磨损机理的影响。结果表明:铝合金摩擦系数随着下模加热温度的升高而增大,磨损机制由300 ℃时的黏着磨损转变为500 ℃时的黏着磨损、氧化磨损和磨粒磨损;施加法向载荷越大,摩擦系数越大,不同载荷下磨损机制均为黏着磨损及轻微的磨粒磨损,且随着载荷增大,黏着磨损程度有所加深;高滑动速度导致了磨损表面局部氧化物的生成,使摩擦系数随着滑动速度增大而减小,滑动速度为30 mm·s?1时,磨损机制主要是氧化磨损、磨粒磨损和黏着磨损。      

High-temperature friction of refractory compounds

The paper overviews long-term studies into the behavior of metallic (carbides, borides, and nitrides of transition metals), and nonmetallic (boron and silicon carbides, aluminum nitride) refractory compounds as well as composite materials based on them in high-temperature friction in vacuum and air. The friction characteristics (wear rate and friction coefficient) are indicated as a function of temperature in the range from room temperature up to 1000–1400 °C. Data of x-ray examination and electron microscopy of friction surfaces are cited. The fracture mechanism for contacting surfaces of materials in friction is considered. __________ Translated from Poroshkovaya Metallurgiya, Vol. 47, No. 1–2 (459), pp. 167–178, 2008.     

Grain boundary segregation of an Al-Zn-Mg ternary alloy

Auger electron spectroscopy (AES) has been used to measure the grain boundary concentration profiles of alloy additions in an A1-5.5 pct Zn-2.5 pct Mg ternary in as-quenched, under-, peak-, and over-aged conditions. The AES depth profiles show marked segregation of Mg and Zn to the grain boundary, in contrast to that reported previously on similar A1 alloys. It is found that this apparent contradiction can be resolved by exploiting the plasmonloss features of the AES spectra to help elucidate the grain boundary segregation. With the AES/plasmon-loss measurements, one can determine not only the concentration of Mg and Zn at the grain boundary, but also the metallurgical environments surrounding the alloy additions. It is shown that, for over-aged specimens of the Al alloy, only a fraction of the total Mg at the grain boundary is incorporated in MgZn₂ precipitates, the remainder being segregated to within a few atomic layers of the boundary.     

High-temperature friction of alloys of the TiNx-TiB2 system

Conclusions It has been established that the highest transverse rupture strength and wear resistance combined with the lowest coefficient of friction are shown by alloys of eutectic composition. In alloys of the TiN_0·9-TiB₂ system higher ductility during friction is exhibited by the boride phase, whose substructure experiences greater changes compared with the nitride phase. The greatest deformation during friction characterizes the phases in the TiN_0·73-TiB₂ alloy. The strengthening and strength loss processes at temperatures of 20–400°C are determined by the strength loss processes occurring in the boride phase, and those above 400°C, by the strengthening and strength loss processes taking place in the nitride phase.Translated from Poroshkovaya Metallurgiya, No. 2(242), pp. 70–76, February, 1983.     

Comparison of the corrosion and stress-corrosion behavior of a ternary Al-Zn-Mg alloy

A comparison has been made of the corrosion and stress-corrosion behavior of an aged Al-5.3 wt pet Zn-2.5 wt pct Mg alloy in aqueous chloride solutions of varying pH (i.e., 1 to 6.2). It is found that lowering the pH to values 〈4 accelerates corrosion in the absence of stress, due to enhancement of the overall cathodic process, and accelerates the propagation of stress-corrosion cracks. However, the pH dependence of cracking is not as marked as the pH dependence of corrosion rate, and this difference has been explained in terms of local variations in pH within the crack. It is concluded that the present observations are consistent with the view that the propagation of stress-corrosion cracks in this metal-environment system involves localized anodic dissolution of the plastically deforming solid solution within the precipitate-free zone.