水/油润滑条件下PTFE复合材料的摩擦学性能

将碳纤维(CF)和锡青铜粉(Cu)分别添加到聚四氟乙烯(PTFE)中制备了两种PTFE复合材料,并将其与42CrMo钢环形成摩擦副,研究了两种PTFE复合材料在干摩擦、水润滑和油润滑条件下的摩擦学性能,并用扫描电子显微镜观察了两种复合材料的磨损表面形貌,分析了磨损机理。结果表明:在干摩擦和油润滑条件下,随着碳纤维含量的增加,CF/PTFE复合材料的摩擦因数增大,磨痕宽度减小;两种PTFE复合材料在干摩擦条件下的摩擦因数最大,油润滑条件下的摩擦因数最小;而且在油润滑条件下,两种PTFE复合材料的磨痕宽度最小;水润滑条件下的摩擦因数比干摩擦的的要小,但磨痕宽度比干摩擦时的要大;CF/PTFE复合材料的磨损机理主要为疲劳磨损,犁沟形貌不明显;Cu/PTFE复合材料的磨损机理主要为磨料磨损,犁沟形貌明显,伴有疲劳磨损。     

VCp/Fe复合材料的耐蚀性研究

采用原位反应铸造法制备了VCp/Fe复合材料.利用X射线衍射、X射线能谱对复合材料的相结构和微区成分进行了分析;利用金相显微镜、扫描电子显微镜对复合材料的微观组织进行了观察.通过测定复合材料及对比材料在1M H2SO4中(25℃)的阳极极化曲线,表明VCp/Fe复合材料的致钝电位Ecr与不锈钢(Cr18Ni9)接近,显著小于白口铸铁(15Cr3Mo),说明复合材料易于钝化;同时复合材料的钝化区域较宽,其钝化膜比较稳定,有较好的抗电化学腐蚀性能.98%浓硫酸和3.5%NaCl水溶液浸泡实验证明,复合材料的腐蚀速度与不锈钢相当,远小于白口铸铁,耐蚀性能优异.     

PTFE微粉/CF改性PEEK复合材料的摩擦磨损性能

为解决核电水循环系统中鼓型旋转滤网驱动装置的耐腐蚀问题,本文研究了碳纤维和聚四氟乙烯微粉改性的聚醚醚酮复合材料在干摩擦、水润滑和油润滑条件下的摩擦磨损性能.通过机械共混、高温模压的方法,制备了不同质量分数的聚四氟乙烯(PTFE)微粉/碳纤维(CF)/二硫化钼(MoS_2)/聚醚醚酮(PEEK)复合材料.采用拉伸试验机和塑料洛氏硬度计测试其力学性能,采用摩擦磨损试验机测试了复合材料在干摩擦、水润滑和油润滑条件下的摩擦磨损性能,采用扫描电子显微镜对其摩擦表面形貌进行分析.结果表明:复合材料在水润滑和油润滑时摩擦系数及磨痕宽度均较小,但水润滑时摩擦系数波动幅度较大且磨痕宽度略高;复合材料在干摩擦条件下的磨损机制以磨粒磨损为主,伴有疲劳磨损,油润滑时摩擦面可形成连续的润滑膜而保持光滑,水润滑时水流冲刷破坏了摩擦面上固体润滑膜的稳定性;CF质量分数增加时,复合材料的洛氏硬度和压缩强度递增,压缩强度达到164 MPa,PTFE微粉质量分数增加时,复合材料的洛氏硬度和压缩强度递减;CF质量分数增加时,复合材料的干摩擦系数及磨痕宽度下降,PTFE微粉质量分数增加时,复合材料的干摩擦系数下降,达到0.17.     

玻璃纤维增强聚醚醚酮复合材料在水润滑下的摩擦学性能

利用球盘式摩擦磨损试验机考察了玻璃纤维(GF)增强聚醚醚酮(PEEK)复合材料在干摩擦和水润滑条件下的摩擦磨损性能,并探讨了其磨损机理。结果表明:在干摩擦和水润滑条件下,PEEK和GF/PEEK的摩擦因数和磨损率均随载荷和对磨时间的增加逐渐增大并趋于稳定,GF的加入可以显著降低GF/PEEK复合材料的摩擦因数和磨损率;在水润滑条件下,PEEK和GF/PEEK的摩擦因数和磨损率比干摩擦下显著降低。干摩擦下,PEEK以黏着磨损和磨粒磨损的混合磨损形式为主,水润滑条件下,磨损方式主要是以轻微的黏着磨损为主;干摩擦下,GF/PEEK磨损表面有大量的微观断裂裂纹和破碎,以磨粒磨损和疲劳磨损为主,水润滑条件下,磨损表面仅有微观切削的痕迹,磨损方式以轻微磨粒磨损为主。由于水的冷却和润滑作用,使得复合材料向对偶钢球的黏着转移明显减弱,同时阻止了对偶钢球上的Fe向复合材料磨损表面转移,从而减轻摩擦、降低摩擦表面温升,显著改善复合材料的摩擦磨损性能。     

稀土改性玻璃纤维对PTFE复合材料摩擦磨损性能的影响

分别用硅烷偶联剂SG-Si900(SGS)、含SG-Si900的稀土溶液(SGS/RES)和稀土溶液(RES)对玻璃纤维进行表面改性,考察了稀土改性玻璃纤维填充的PTFE复合材料在油润滑条件下的摩擦磨损性能,并用扫描电子显微镜(SEM)分析了磨损表面形貌.结果表明:与未经表面改性玻璃纤维填充的PTFE复合材料相比,经表面改性玻璃纤维填充的PTFE复合材料的减摩耐磨性能得到提高,以RES的作用最明显,SGS/RES次之,SGS第三;在油润滑条件下,稀土改性玻璃纤维填充的PTFE复合材料只出现了轻微磨损,这是由于玻璃纤维经稀土表面改性后极大地改善了玻璃纤维与PTFE基体之间的界面结合力,使稀土改性玻璃纤维填充的PTFE复合材料具有优异的摩擦磨损性能.     

碳毡/铜复合材料的摩擦磨损特性研究

本文研究了用电沉积法制备的碳毡/铜复合材料的摩擦磨损特性。研究结果表明,在干摩擦条件下,复合材料的耐磨性主要与摩擦副间维持连续有效碳膜时间的长短有关,该时间取决于碳毡纤维的体积分数。在油润滑条件下,碳毡/铜复合材料的耐磨性与复合材料的硬度及纤维弯曲和破断所消耗能量的多少有关。在这两种条件下,复合材料的耐磨性均明显优于常用耐磨铜合金ZQSn6-6-3.     

AlNP/Al和TiB2P/Al复合材料摩擦磨损性能研究

研究了油润滑条件下两种不同铝基复合材料及其基体合金的摩擦磨损性能,分析了增强体对材料摩擦磨损性能的影响以及相应的磨损机理.结果表明:油润滑条件下,随着摩擦时间的延长,AlNP/Al复合材料的摩擦系数由小变大趋于稳定;而TiB2P/LY12复合材料的摩擦系数却是由大变小趋于稳定,这主要与其摩擦过程中形成凹坑产生润滑油膜有关.由于增强体强度的增加,50%(体积分数,下同)TiB2P/Al复合材料的摩擦系数低于50%AlNP/Al复合材料,且耐磨性优于50%AlNP/LY12复合材料.增强相的加入显著提高了材料的耐磨性,使得复合材料的抗粘着能力明显优于基体合金.     

类金刚石薄膜在干摩擦、油和脂润滑条件下的摩擦学性能分析

通过钢/类金刚石(DLC)薄膜摩擦副在干摩擦4、122油和L252脂润滑条件下的球-盘摩擦学试验,对比分析润滑条件、载荷、速度对DLC膜摩擦系数的影响,利用原子力显微镜分析膜层磨损性能,研究润滑条件对膜层磨损寿命的影响。结果表明:油、脂润滑下DLC膜最大静摩擦系数分别减小了17%和38%;从0～2000 r/min转速范围内,DLC膜摩擦系数随转速增加而减小,油润滑下相比干摩擦DLC膜摩擦系数小15%～48%,脂润滑下相比干摩擦DLC膜摩擦系数在0～500 r/min转速范围小,超过500 r/min后干摩擦DLC膜摩擦系数小;油和脂润滑条件下,DLC膜层的磨损程度明显降低,磨损率相比干摩擦条件下分别减小了7.4倍和15.5倍。     

石墨改性热塑性聚酰亚胺复合材料的摩擦磨损性能

采用热压成型工艺制备石墨填充热塑性聚酰亚胺复合材料,考察了复合材料的力学性能及干摩擦和三种油润滑条件下的摩擦磨损性能;利用扫描电子显微镜和能谱仪观察分析材料磨损表面形貌和元素分布.结果表明:石墨的加入降低了复合材料的弯曲强度和拉伸强度,干摩擦条件下复合材料摩擦系数随着石墨含量的增大稳步降低最终保持在0.1左右;石墨含量为30%时复合材料磨损率仅为纯树脂的2.9%;油润滑条件下复合材料的摩擦系数相比干摩擦降低了一个数量级;三种润滑油均能在偶件表面形成稳定吸附膜,由于润滑油性质的差异导致材料摩擦磨损性能有所不同.     

放电等离子烧结WC/Fe复合材料摩擦磨损性能

采用放电等离子烧结技术制备了WC质量分数为40%的WC/Fe复合材料,研究了不同烧结温度条件下WC/Fe复合材料的致密度、组织、硬度及干摩擦磨损性能。利用SEM和XRD分析了不同烧结温度条件下存在的物相;采用销-盘摩擦磨损试验机(盘试样选用~80μm的Al2O3砂纸,滑动距离约为950m)测量了马氏体耐磨钢和WC/Fe复合材料在不同载荷下相对磨损率;用SEM观察磨损形貌,确定WC/Fe复合材料的磨损机制。结果表明:烧结温度为1080℃时,WC/Fe复合材料实现完全致密,WC陶瓷颗粒均匀分布在基体中并与基体界面结合良好;随着WC/Fe复合材料完全致密化,其硬度及耐磨性能逐渐提高;WC/Fe复合材料的耐磨性能远优于马氏体耐磨钢。WC/Fe复合材料磨损机制主要为氧化磨损和磨粒磨损。在低载荷条件下,颗粒脱离基体造成氧化膜破裂,促使材料表面受损;较高载荷条件下,WC陶瓷颗粒破碎加速氧化膜破裂,加快了材料的磨损。     

Erosive Wear and Wear Mechanism of in situ TiCp/Fe Composites

1.IntroductionMetal-based composite is a kind of environmental ma-terial that can be reused.It combines the beneficialproperties of the metal matrix,such as ductility,goodthermal and electrical conductivity and high toughness,with those of the reforcement phase[1~3].The latter isusually a ceramic,serving to increase the elastic modu-lus,shear strength and hot strength,fatigue and wearresistance.Its development has been widely studied[4~8].Wear of metal materials causes a tremendous loss of ec…     

不同类型颗粒混合增强铁基复合材料的磨损性能

采用电流直加热动态热压烧结工艺制备陶瓷颗粒增强铁基复合材料,研究高体积分数(25%,30%,35%)下,单一类型颗粒(SiC,TiC,TiN)及混合类型颗粒(TiC+TiN,SiC+TiN,SiC+TiC)作为增强相对铁基复合材料磨损性能的影响。结果表明:单一类型粒子强化时,TiNP/Fe复合材料的耐磨性最好,TiCP/Fe次之,SiCp/Fe最差。混合粒子作为增强体时,(TiC+TiN)P/Fe复合材料磨损性能显著优于其对应的单一颗粒增强材料;其中粒子含量为30%时,(TiC+TiN)P/Fe复合材料磨损性能提高最大,其磨损量比TiCP/Fe降低了51.9%,比TiNp/Fe复合材料降低了44.1%,体现出可贵的混合增强价值。(SiC+TiC)_P/Fe和(SiC+TiN)P/Fe复合材料的磨损性能分别处于对应的两个单一颗粒增强材料之间。磨损表面观察表明,耐磨性好的(TiC+TiN)P/Fe复合材料的磨损机理为磨粒磨损,而(SiC+TiC)_P/Fe和(SiC+TiN)P/Fe复合材料除磨粒磨损外还存在明显的疲劳磨损现象。     

TiC增强复合材料在不同条件下的磨损行为

研究了TiC/NiCrMoAlTi金属陶瓷、TiC/NiMo金属陶瓷和钢结TiC硬质合金的磨损行为,结果表明:在平稳加载条件下,金属陶瓷的耐磨性优于钢结TiC硬质合金;而在冲击载荷条件下,钢结硬质合金的室温耐磨性优于金属陶瓷,但在高温下金属陶瓷的耐磨性又转为优于钢结硬质合金,与室温相比TiC/NiCrMoAlTi和TiC/NiMo的耐磨性分别提高31%和79%,而钢结TiC硬质合金则下降52%.初步分析了不同粘结相的TiC增强复合材料的磨损机制以及加载率和温度对磨损行为的影响.TiC增强复合材料的磨损行为与其使役条件密切相关.     

Ti诱导反应熔体无压浸渗法制备(W,Ti)C/Fe复合材料

研究了一种Ti诱导反应熔体无压浸渗制备复合材料的方法: 通过凝胶注模成型工艺, 以蔗糖为造孔剂制备了多孔Ti-WC陶瓷骨架预制体, 真空状态下, 在1370℃以Fe-Cr-C合金熔体无压浸渗该预制体, 经过原位反应制备了(W,Ti)C/Fe复合材料。利用SEM-EDS、 XRD对复合材料的组织结构、 元素组成及相组成进行了测试和分析。采用旋转圆盘式摩擦试验机以SiC砂浆为磨料研究了(W,Ti)C/Fe复合材料的耐磨性。结果表明: 在浸渗过程中骨架中的Ti元素的溶解析出与C元素的原位反应促进了浸渗过程的进行, 在1370℃保温1 h, 金属液即渗透整个多孔骨架, 并且在浸渗过程中仍然维持着骨架的形状, 浸渗过程中Ti-C-WC原位反应生成具有芯-壳结构的中间富Ti、 边缘富W的(W,Ti)C增强相。摩擦磨损实验结果表明, (W,Ti)C/Fe复合材料具有优异的抗磨粒磨损性能, 其耐磨性优于工业用耐磨铸铁。     

Microstructure and abrasive wear behaviour of iron base hardfacing

Abstract

The influence of the composition and heat treatment of overlays on the abrasive wear resistance of iron base hardfacing alloy overlays is reported. Overlays were deposited using a shielded metal arc (SMA) welding process on structural steel using two commercial hardfacing electrodes, i.e.Fe – 6%Cr – 0.7%C (H₁) and Fe – 32%Cr – 4.5%C (H₂). Abrasive wear resistance of overlays in as welded and heat treated conditions was tested using a pin on disc system against a 300 grade waterproof SiC polishing paper at different normal loads (1 – 4 N) and constant sliding speed 2.0 m s^-1. Optical microscopy was used to study the microstructure of overlays in as welded and heat treated conditions. SEM studies of wear surfaces were carried out to analyse wear mechanisms. It was found that the wear resistance of the high Cr – C coating is better than the low Cr – C hardfacing under identical conditions. Significant variation in hardness was noticed across the interface, indicating the effect of dilution. Hardness of the coating adjacent to the interface was found to be comparatively lower than the coating further away from the interface. Post-weld heat treatment enhanced the abrasive wear resistance.     

白炭黑的功能化改性及其改性橡胶基复合材料的制备与表征

利用沉淀法白炭黑生产工艺,在相同的条件下,选用不同质量分数的羟基羧酸酯作为改性剂进行湿法改性,研究了白炭黑/天然橡胶(NR)复合橡胶的力学性能、动态性能以及动态生热性能。结果表明:制备的白炭黑均为非晶态白炭黑,采用质量分数为6%的羟基羧酸酯改性的白炭黑,其分散性好,颗粒分布均匀,呈近球状,经羟基羧酸酯改性后的白炭黑有效的去除了部分亲水基团,改善了其在NR中的分散性。随着白炭黑用量的增加,分散性变差,损耗因子和动态温升均有所提高,Payne效应增大。当白炭黑用量达到临界值(白炭黑与NR质量比为40∶100)时,白炭黑/NR复合材料表现出较好的性能,改性白炭黑/NR复合材料比未改性白炭黑/NR复合材料的硬度、拉伸强度、断裂伸长率有所提高,而磨耗体积和动态生热则有所下降。动态力学性能测试结果表明,改性白炭黑与天然橡胶的质量比为40∶100时,改性白炭黑/NR复合材料的60℃滚动阻力损耗因子由0.123降到0.104。SEM结果表明,改性白炭黑在橡胶基体中的分散性优于未改性白炭黑,与NR基体界面结合的更加紧密。     

Effects of particulate reinforcement and heat treatment on the hardness and wear properties of AA 2024-MoSi2 nanocomposites

In this study, nanocomposites of AA 2024 aluminum alloy matrix reinforced with different volume fractions of nanometric MoSi₂ intermetallic particles ranging from 0 to 5%, were produced using mechanical alloying technique. For comparison, samples without reinforcing particles and mechanical alloying and a sample with micrometric MoSi₂ particles were also synthesized. The prepared composite powders were consolidated by cold and hot pressing and then heat treated to solution and aged condition (T6). The effects of MoSi₂ particle size, volume fraction and also heat treatment on the hardness and wear properties of the composites were investigated using Brinell hardness and pin-on-disc wear tests. The results indicated that although T6 heat treatment increases the hardness of all samples compared to as hot-pressed (HP) condition, the age-hardenability (aging induced hardness improvement) decreases after mechanical alloying and with increasing MoSi₂ volume fraction due to the high dislocation density produced during mechanical alloying. With increasing the volume fraction of nano-sized MoSi₂ particles up to 3–4%, the hardness of the composites continuously increases and then declines most probably due to the particle agglomeration. The wear sliding test disclosed that the wear resistance of all specimens in T6 condition is higher than that of HP condition and increases with increasing MoSi₂ content. Scanning electron microscopic observation of the worn surfaces was conducted and the dominant wear mechanism was recognized as abrasive wear accompanied by some adhesive wear mechanism.     

Influence of plasma nitriding on rolling–sliding wear of Fe–Mo sintered steels

Abstract

Dry rolling-sliding tests were carried out on plasma nitrided and heat treated Fe–Mo–C sintered alloys. Whereas the heat treated alloy undergoes oxidative wear independently of the load condition and duration of the test investigated, the plasma nitrided alloys show distinct wear stages characterised by different wear rates. In particular, while the white layer is able to remain in place the wear rate is lower than that shown by the reference heat treated material. The durability of the white layer increases on decreasing the applied loads and/or submitting the materials to heat treatment before plasma nitriding, to improve the load bearing capacity of the subsurface layers. Fatigue cracks nucleate in the subsurface layers because of the stress concentrating effect of pores, but no fatigue wear was observed during the tests. After loss of the white layer due to oxidation or microcracking, the wear rate increases because both oxidation and plastic shearing control the wear behaviour.

MST/2067