4种成分车轮钢与U71Mn钢轨钢间的磨损行为

在轮轨磨损试验机上研究了热轧U71Mn钢轨钢和4种成分车轮钢间的摩擦磨损行为,分析了车轮钢化学成分、硬度对磨损行为及磨损机制的影响。结果表明:随着碳元素含量的提高,车轮钢显微组织中先共析铁素体含量显著减少,珠光体晶粒尺寸增大,珠光体中的渗碳体片层变厚,车轮钢的硬度也逐渐增大;随着车轮钢硬度的增大,车轮钢磨损量减少,其主要磨损机制由磨粒磨损和浅层剥层磨损向深层剥层磨损转变,钢轨钢磨损量增加,其主要磨损机制为浅层剥层磨损。     

两种不同组织类型相同强度级别低合金高强钢的耐磨性

利用摩擦磨损试验机和自由磨料式腐蚀磨损试验机,在不同的润滑、载荷和腐蚀条件下,对两种组织类型不同、但抗拉强度同为700 MPa级别的S700和M700低合金高强度钢的滑动耐磨性和腐蚀耐磨性进行了研究,并分析了磨损机理。结果表明:S700钢的组织为铁素体+贝氏体,M700钢的组织为铁素体+珠光体;S700钢的硬度略高于M700钢的;在相同的滑动磨损条件下,S700钢的磨损量小于M700钢的;试验钢在酸性溶液中的腐蚀耐磨性均较差;在相同的腐蚀磨损条件下,S700钢的腐蚀耐磨性优于M700钢的;两种试验钢的滑动磨损机制主要是微观切削和塑性变形,酸性条件下的腐蚀磨损形貌为大面积的腐蚀坑且伴随剥落,而碱性条件的则以微观切削为主,并伴有少许的剥落。     

45钢中渗碳体形态对耐磨性的影响

本文研究了46钢等温处理得到的片状珠光体和调质处理得到的粒状珠光体的耐磨性。试验结果表明:在相同的热处理温度或相同硬度的条件下,片状珠光体的耐磨性均高于粒状珠光体;粒状珠光体的磨损量随回火温度的变化呈马鞍形,500℃左右磨损量最少,650℃及450℃时磨损量都较大。渗碳体形态对45钢耐磨性的影响可能与片状珠光体比粒状珠光体容易氧化有关。而粒状珠光体磨损量的马鞍形是由表层塑性变形、表面裂纹的形成与扩展等因素决定的。     

材质对谐波减速器刚轮的耐磨性能影响

采用3种谐波减速器用刚轮材料——2Cr13不锈钢、40Cr中碳合金钢、45钢,通过对其显微组织、硬度、三维及二维形貌的显微磨损、摩擦因数的分析,探究不同材料耐磨性能的差异。结果表明,2Cr13、40Cr的显微组织为回火索氏体,45钢的显微组织为铁素体与珠光体。2Cr13、40Cr硬度相近且远大于45钢。2Cr13磨损形貌为黏着与剥落,磨损机制为黏着磨损;40Cr、45钢磨损形貌为犁沟与剥落、犁沟与黏着,磨损机制为磨粒磨损。3种材料的摩擦因数相差可忽略不计。2Cr13、40Cr、45钢截面的磨损面积分别为5 008、1 645、6 535μm2。硬度相近下,40Cr表现出比2Cr13更优异的耐磨性能。45钢与摩擦副材料的硬度值相差最大,耐磨性能最差。     

烧结温度对铁基粉末冶金航空刹车材料摩擦磨损性能的影响

研究了不同烧结温度(900,930,950,980,1020℃)对飞机铁基粉末冶金刹车材料材料显微组织、致密化和摩擦磨损性能的影响。借助于材料组织结构、摩擦试验后的材料表面观察及理论分析,阐述了材料组织结构及摩擦磨损变化的机制。结果表明:900℃的试样由于烧结不够充分,材料密度较低,珠光体的数量较少,硬度低,耐磨性差,经过摩擦试验后,摩擦材料表面大面积剥落和点蚀比较严重,材料磨损量较大,磨屑以大块状及条状为主;930℃试样的材料密度增加,珠光体数量增加,硬度及耐磨性增加,经摩擦试验后,试样表面比较光滑,但仍有大量的点状剥落,材料磨损量较900℃的试样有所降低;当烧结温度由950℃升高至1020℃时,由于原子扩散的加剧,材料的基体具有足够强度,珠光体的数量显著增加,显著提高了材料的耐磨性,经摩擦试验后,材料表面生成了完整的氧化膜,材料的磨损量变化不大,相对于950℃和980℃的试样而言,1020℃时的材料摩擦表面出现更少的点状脱落并形成了多层叠加的工作层。     

高硫合金钢/N80钢在水介质中的摩擦性能学研究

利用MG-200型摩擦磨损试验机研究了高硫合金钢(HS钢)和N80钢的摩擦学性能,用XJP-3A光学显微镜分析了其显微组织及试样磨损后表面形貌,用HV-1000A型显微维氏硬度计分析了其磨损前后的表面硬度.结果表明,HS钢的平均摩擦因数较低,摩擦因数随着时间呈波动特性,并逐渐趋于稳定;HS钢中硫化物致密均匀地呈球状、棒状及网络状向基体延伸,基体为细层片状珠光体加少量马氏体;HS钢表现为微磨粒磨损及轻微的黏着磨损,N80钢呈现机械抛光磨损特征,且两摩擦面上均有黑色物质附着;HS钢在磨损过程中发生轻微的表面加工硬化.     

DH36高强度船板钢的动态CCT曲线

利用Gleeble-2000D型热模拟试验机对DH36高强度船板钢的动态CCT曲线进行了研究。结果表明:当冷速小于1℃.s-1时,DH36钢的组织为铁素体和珠光体;冷速在3～13℃.s-1范围内,得到铁素体、贝氏体和少量珠光体组织;当冷速达到15℃.s-1时,组织为贝氏体和少量铁素体;当冷速达到30℃.s-1时,有马氏体组织生成;DH36钢的显微硬度随着冷速的提高而增大,当冷速达到30℃.s-1时,显微硬度明显增大。     

超声表面滚压处理对45钢摩擦学性能的影响及机理

采用超声表面滚压处理(USRP)技术对45钢表面进行强化处理,通过表面形貌和表层显微组织观察、表面粗糙度和摩擦磨损性能测试,研究了USRP对该钢摩擦学性能的影响及机理。结果表明:USRP试样的表面粗糙度由未处理试样的3.2μm降低到0.23μm;显微组织得到了细化,晶粒取向趋于随机分布,有大角度晶界出现;表面显微硬度比未处理试样的提高约56%,强化层厚度达到400μm;USRP试样的摩擦因数小于未处理试样的,磨损量为未处理试样的1/4;未处理试样磨损过程中表面材料呈"片块状"脱落,磨损机制为黏着磨损,USRP试样磨损表面上存在犁皱形成的沟槽,磨损机制为磨粒磨损。     

新型CL60钢地铁车轮摩擦磨损试验研究

为了提高地铁车轮的服役性能,对车轮用CL60钢材料中Si、Mn、Cr等元素的质量分数进行重新设计和优化,研发新型CL60钢地铁车轮,通过GPM-60摩擦磨损试验机模拟轮轨磨损试验,研究原CL60钢车轮与新型CL60钢车轮在实验室条件下的磨损特性。基于赫兹模拟准则设计计算了模拟试验采用的轮轨试样尺寸、施加的载荷和转速;通过不同载荷工况下的摩擦磨损试验和轮轨材料微观组织分析,研究2种轮-轨试样的磨损量、磨损率、塑性变形及表面形貌的变化规律及特征,对新型CL60钢车轮的使用性能进行评价。结果表明：与原CL60钢车轮相比,在不同载荷下新型CL60钢车轮试样磨损量、轮-轨试样总磨损量、磨损率及摩擦表面塑性变形层厚度均大大降低,其抗磨损性能和塑性变形能力得到了改善。     

退火温度对无铝超高碳钢组织及性能的影响

对名义成分为Fe-1.58C-1.97Cr-0.26Si-0.73Mn-0.09Mo的一种无铝超高碳钢在800~1 100℃进行了退火处理,利用物相分析、显微组织观察、力学性能测试等方法研究了退火温度对该钢显微组织和力学性能的影响。结果表明:退火温度为800℃时,试验钢组织中存在大量的网状碳化物;当退火温度升至860℃时,网状碳化物消失,获得由细小均匀分布的碳化物加珠光体组成的组织;当退火温度进一步升至1 000℃以上时,试验钢中的珠光体组织变得粗大,且再次析出了网状碳化物;随退火温度的升高,试验钢的抗拉强度和冲击功先增大后减小,且均在860℃时达到最大,分别为1 017 MPa和15J。     

The wear resistance and worn metallography of pearlite,bainite and tempered martensite rail steel microstructures of high hardness

In order to find out whether it is worthwhile to produce premium rail steels harder than 36–39 HRC and to discover the best microstructure for wear-resistant rail an experimental Cr-Mo alloy rail steel was heat treated to pearlite, bainite and tempered martensite. Each microstructure was prepared at hardness levels of 38, 42 and 45 HRC. These were tested in a dual disk-on-disk machine that closely simulates wheel-rail contact in curves at 1/10 scale. Wear rates were established for dry, grease-sand and pure grease environments. Dry wear rates decreased significantly with increasing hardness in high rails with tempered martensite or bainite microstructures but were almost independent of hardness for pearlite in the range tested. Lubrication reduced the wear rates by up to two orders of magnitude for all microstructures. It is concluded that pearlite gives the best dry wear performance, and there is no advantage in increasing the hardness beyond 38–40 HRC. The superior performance of pearlite in dry wear appears to be due to a very pronounced work hardening near the wearing surface. Electron microscopy reveals a marked refinement in the pearlite microstructure near the wearing surface, and this may explain the high work hardening observed.     

Wear behaviour of forging steels with different microstructure during dry sliding

Sliding wear behaviour of two types medium carbon microalloyed steels containing various microstructures was investigated on a 320 mesh SiC paper at a sliding speed of 0.33 m/s with a load of 6 N and sliding duration of 4 min under dry sliding conditions (the sliding distance, 80 m). The experimental results showed that the different microstructures cause a great influence on the wear resistance performance of the steels. Water quenched samples with martensite structure have the highest hardness and wear resistance performance. That is because, water cooled samples contained higher amount of carbon in the solid solution. On the other hand, air or sand cooling from forging temperature results in a decrement of hardness and wear resistance in steel-1 and steel-2. However, air cooled samples showed slightly higher wear resistance than sand cooled samples due to finer grain sizes and the larger pearlite and/or precipitation contributions.     

Frictional hardening and softening of steel 52100 during dry sliding

The behavior of frictional hardening and softening of steel 52100 with different microstructures during dry sliding was studied based on dynamic metallographic analysis. It was demonstrated that such frictional behavior significantly affected wear resistance of the steel. The results showed that anti-softening microstructures exhibited a rather better wear resistance; the difference in the wear resistance of various steels with different microstructures was caused by the difference in the energy consumption in surface layers during wear. These results indicate that the original structures and properties of steels should not be taken as the only criterion for judging the wear resistance. It is necessary to consider the influence of dynamic microstructural changes under specific wear conditions in order to evaluate the wear resistance.     

Effect of Titanium and Nitrogen Additions on the Microstructures and Three-Body Abrasive Wear Behaviors of Fe–B Cast Alloys

This study investigates the effect of titanium and nitrogen elements on the microstructures and wear behaviors of medium carbon Fe–B cast alloy. The as-cast microstructures of Fe–B cast alloy consist of the eutectic boride, pearlite, and ferrite. Moreover, the as-cast eutectic boride structures are greatly refined when titanium and nitrogen are added. The boride area fraction, average boride area, Rockwell hardness, etc., are also investigated systemically. The wear behaviors of medium carbon Fe–B cast alloy are studied by a three-body abrasive wear tester. The results show that the wear weight loss of Fe–B cast alloy with titanium and nitrogen elements is lower than that of the ordinary Fe–B cast alloy. Meanwhile, the wear mechanism of Fe–B cast alloy with different titanium and nitrogen concentrations is described and analyzed.     

Investigations on Microstructures and Two-body Abrasive Wear Behavior of Fe–B Cast Alloy

The microstructures of Fe–B alloys containing different carbon and boron concentrations have been investigated. The solidification microstructures of Fe–B alloy consist of the eutectic boride, pearlite, and ferrite. Borides precipitate along the grain boundary during the formation of eutectic. After heat treatment, the phases in Fe–B alloy are composed of the boride and martensite. With increase of carbon and boron concentrations, the Rockwell hardness of Fe–B alloy becomes larger. Meanwhile, by using a pin-on-disk abrasion tester, the effects of carbon and boron concentrations on the wear behaviors including ploughing depth, roughness, and wear weight loss under different loads have been studied. The results show that the wear resistance of Fe–B alloy with higher carbon and boron concentrations is comparable with the high chromium white cast iron.     

Characteristics of Extrusive Wear and Transition of Wear Mechanisms in Elevated-Temperature Wear of a Carbon Steel

The dry sliding wear of a medium carbon steel with different microstructures was measured under the normal load range of 50–150 N at 400°C by a pin-on-disc high-temperature wear setup. The wear behavior and wear mechanism were systematically studied; in particular, the characteristics of extrusive wear and the transition of wear mechanisms were investigated. Under low normal loads, the wear is oxidative type wear. Once the normal load reached a critical value, a mild-to-severe wear transition occurred, and subsequently an extrusive wear prevailed. The mild-to-severe wear transition depended on the microstructure of matrix; the critical normal load of the transition was 112.5 N for tempered sorbite, 125 N for lamellar pearlite, and 137.5 N for tempered martensite and tempered troostite. As oxidative wear prevailed, a thick oxide layer about 20–30 μ m and a plate-like wear debris with regular outline were recognized. However, as the extrusive wear occurred, the wear rate abruptly increased but the friction coefficient was reduced. The extrusive wear predominated due to thermal softening of the matrix and presented a superthin oxide layer (less than 0.5 μ m) and low oxide content on worn surfaces, accompanied by the appearance of ribbon-like wear debris.     

铝合金表面Ni-SiC复合镀层的摩擦磨损性能

通过复合电沉积技术,在铝合金表面得到了不同SiC粒子含量的Ni-SiC复合镀层,研究了在干摩擦和液态石蜡润滑摩擦条件下载荷与SiC粒子体积分数对Ni-SiC复合镀层摩擦磨损性能的影响。结果表明:无论在干摩擦或润滑摩擦条件下,加入SiC粒子后的复合镀层其耐磨性均优于纯镍镀层,并随载荷的提高耐磨性下降。在干摩擦条件下,镀层中的SiC粒子体积分数在5.8％时复合镀层耐磨性最好;在润滑摩擦条件下,随镀层中SiC粒子体积分数提高,复合镀层耐磨性均提高。     

Erosion of AISI 4140 steel

The erosion behavior of AISI 4140 steel under various heat treatment conditions was investigated. A variety of microstructures, such as the primary and tempered martensites, varying proportions of martensite and bainite, cementite spheroids embedded in a ferrite matrix and ferrite and pearlite were obtained. The erosion tests were performed in a sand-blast-type test rig. Except in the region where temper embrittlement occurred, the erosion decreased with increasing tempering temperatures. Erosion decreased with the increasing percentage of bainite in the austempered condition and also with increasing tempering time during spheroidization. From the point of view of the mechanical properties, erosion decreased with increasing ductility and decreasing hardness or ultimate strength. The abraded surfaces were also studied using scanning electron microscopy.     

激光强化参数对40Cr钢表面组织及摩擦性能影响的研究

采用CO2横流式激光器对40Cr材料进行表面强化处理研究;使用S-360型扫描电镜观察激光硬化区金相组织及成分并观察金属表面磨损形貌;采用CHX-1超显微硬度计测量激光强化区断面的显微硬度;然后在MPX-2000盘销式摩擦磨损实验机上进行干摩擦和油润滑实验。结果表明:激光参数对表面硬度和硬化层深度有很大影响,较大的功率可使奥氏体转变充分而获得更多的马氏体,激光扫描速度越快,功率越大,显微硬度越高,硬化层越深;少量针状马氏体组织化引起表层强化,经激光硬化的表面其耐磨性可大大提高;40Cr在干摩擦条件下的平均磨损量是润滑时的5倍,40Cr和20MnSiV的磨损主要以磨粒磨损为主,同时也有粘着磨损。     

Effect of phosphide and matrix microstructures on the dry sliding wear of grey cast iron

The effect of a continuous phosphide network in matrices of pearlite, ferrite, martensite, and tempered martensite has been investigated on the dry wear of a grey iron, sliding at a speed of 1.5 m s⁻¹ with stresses of 0.5 and 2.0 MPa against cast iron. A running-in period was observed with a 0.2% P iron, whereas no running-in was observed with the 1.0% P irons. The presence of a continuous phosphide network reduced the wear rate of the pearlite iron by a factor of 0.25. In the weaker matrices (pearlite, ferrite, and tempered martensite) the phosphide network stiffened the matrix, fractured, and formed a particulate composite of phosphide in the deformed surface which resisted deformation. The wear rates and wear mechanisms of the irons are presented and discussed.