载荷对MoSi_2/Si_3N_4配对副高温磨损性能的影响

在XP-5高温摩擦磨损试验机上考察了MoSi2/Si3N4配对副在1 000 ℃、0.126 m/s滑动速度以及不同载荷条件下的摩擦磨损性能,通过扫描电子显微镜(SEM)和X射线衍射仪(XRD)对MoSi2/Si3N4配对副磨损表面进行了分析.结果表明:MoSi2/Si3N4配对副在1 000 ℃高温滑动时,MoSi2的摩擦因数随载荷的增大而降低,其磨损率则呈上升的趋势;随着载荷的增加,MoSi2的磨损机制依次表现为氧化、粘着、研磨和疲劳断裂.Si3N4盘的主要磨损形式为粘着和氧化,氧化增重引起其磨损率为负值.     

碳/碳复合材料的载流摩擦磨损性能及机理

在高速载流摩擦磨损试验机上对碳/碳复合材料进行摩擦磨损试验,研究了不同电流、载荷和滑动速度下复合材料的摩擦因数、磨损率及磨损表面形貌,并分析了磨损机理。结果表明:在一定载荷作用下,随电流和滑动速度增大,碳/碳复合材料的摩擦磨损性能先保持良好而后趋于恶化;在电流和滑动速度一定的条件下,较低和较高的载荷都会恶化碳/碳复合材料的摩擦磨损性能;随着摩擦表面温度升高,碳/碳复合材料基体开始氧化流失,碳纤维脱落形成磨屑,从而导致磨粒磨损;随后摩擦表面的高温使磨屑软化,磨屑在机械应力作用下逐渐被碾压成碳膜,形成粘着磨损;磨损表面温度的进一步升高以及高速冲击的作用破坏了碳膜的完整性,从而恶化了碳/碳复合材料的摩擦磨损性能。     

复合镀层的摩擦磨损特性研究

研究了Ni-W-Co/SiC复合镀层的干摩擦滑动磨损特性,分析了载荷、滑动速度及滑动距离对磨损机制的影响。试验结果表明,磨损表面生成稳定的氧化膜将导致磨损机制发生转化。     

不同温度下MoSi2的高温磨损行为研究

采用XP-5型高温摩擦磨损试验机考察了MoSi2/Al2O3配对副在700～1100℃间的摩擦学性能.利用扫描电子显微镜和X射线衍射仪观察与分析了MoSi2的磨损表面与相组成.结果表明:MoSi2/Al2O3摩擦副低于900℃时摩擦因数随温度升高而增加,MoSi2的磨损率较低,氧化与粘着磨损是MoSi2的主要磨损形式;高于900℃时摩擦因数略有下降,但基本维持在0.6～0.8之间, MoSi2的磨损率却显著增加,这是由于塑脆转变特性的影响,MoSi2磨损表面还发生磨粒磨损、变形与断裂,粘着和氧化磨损加剧;偶件Al2O3的磨损形式为粘着磨损.     

Ekonol/石墨/MoS2填料对PTFE力学和摩擦磨损性能的影响

研究了Ekonol含量对Ekonol／石墨／MoS2／P，PTFE复合材料的力学性能、摩擦磨损性能的影响，以及滑动速度、载荷对材料摩擦磨损性能的影响；用扫描电子显微镜观察了复合材料磨损后的表面形貌，并探讨了其磨损机制。结果表明：加入填料降低了材料的拉伸强度和弯曲强度，但提高了弯曲模量和硬度；同时填料能提高材料的磨损性能，但使摩擦因数升高了；当Ekonol含量较低时，磨损机制为粘着磨损，随着填料含量的增加，Ekonol分散到基体中，起到了承载作用，阻止了PTFE基体的带状破坏，磨损机制为疲劳磨损和轻微的粘着磨损；摩擦因数随载荷的增大而减小，随滑动速度的增大而增大，在相同的滑动时间内，磨痕宽度随载荷和滑动速度的增大而增大。     

PCrNiMo材料摩擦磨损特性研究

采用自制的销盘式干滑动摩擦磨损试验机，研究了不同硬度炮钢材料PCrNiMo自配副时的摩擦磨损特性。研究结果表明：材料的磨损率随着速度、载荷的增加而增大，摩擦因数随着速度、载荷的增加而减小；低速低载条件下，接触表面以磨粒磨损为主，而在高速、高载条件下，接触表面以粘着磨损形式为主。     

干摩擦和水润滑条件下单晶硅的摩擦磨损性能研究

在UMT-2微摩擦试验机上,对单晶硅片进行了干摩擦和水润滑两种状态下的摩擦磨损试验,分析讨论了载荷和滑动速度对单晶硅片的摩擦因数和磨损率的影响规律;运用扫描电子显微镜,观察和分析了其磨损表面形貌。结果表明:干摩擦条件下的磨损机理主要表现为黏着磨损,水润滑条件下的磨损机理主要表现为机械控制化学作用下的原子/分子去除过程;水润滑条件下的摩擦因数和磨损量均较小,最小磨损率仅为10μm3/s;在水润滑条件下,载荷和滑动速度达到一定值时,硅片表面将发生摩擦化学反应,生成具有润滑作用的Si(OH)4膜,即机械作用在一定条件下对化学反应具有促进作用。     

往复滚动工况下车轮钢磨损机制研究

利用往复滚动试验装置,对不同制动状态和频率下的车轮钢摩擦磨损机制进行了研究.结果表明:随切向摩擦力的增加,滚动摩擦副间的相对滑动量、摩擦因数和线接触区域的拉压应变相应变大,车轮钢平面试样表面的损伤形式呈现从擦伤到磨粒磨损再到粘着和疲劳剥离的变化规律;摩擦因数一定时,随频率的增加,磨损形式由磨粒磨损逐渐向疲劳磨损转变.     

高速干滑动条件下钢/铜摩擦副摩擦磨损表面摩擦热规律研究

利用MMS-1G高温高速销-盘摩擦磨损试验机,以钢/铜摩擦副为研究对象,进行摩擦磨损试验,使用热电偶对摩擦表层进行测温,应用JSM-5610LV型扫描电子显微镜对摩擦表面进行观察,研究在高速干摩擦条件下摩擦热的影响因素及对表面磨损机制的影响。结果表明:摩擦表面的温度随着速度、载荷的增加而增加;在摩擦初期摩擦温度显著增加,摩擦因数快速下降,当达到某一数值后形成一个动态的平衡;随着摩擦温度的升高,磨损机制发生转变,由粘着磨损转变为磨粒磨损和粘着磨损共同作用。     

层状WC/TiC陶瓷刀具材料与轴承钢的摩擦磨损性能

采用雾化-喷覆液膜-干燥工艺及真空热压烧结技术制备了层状WC/TiC陶瓷刀具材料,在干摩擦条件,将其与GCr15轴承钢进行了摩擦磨损实验,研究了不同滑动速度和不同载荷对其摩擦系数和磨损量的影响规律,并对其摩擦磨损后的表面形貌进行了分析。结果表明:在相同载荷条件下,材料的摩擦系数和磨损量均随滑动速度的升高而减小,当滑动速度为12m/min时,材料的摩擦系数和磨损量最小,其值分别为0.276和0.68×10^-3mm^3;在相同滑动速度条件下,材料的摩擦系数和磨损量也均随载荷的增大而减小,载荷为120N时,材料的摩擦系数和磨损量最小,其值分别为0.157和0.58×10^-3mm^3;材料的磨损机理主要是粘着磨损和磨粒磨损。     

Effects of Normal Load,Sliding Speed,and Surface Roughness on Tribological Properties of Niobium under Dry and Wet Conditions

The effects of normal load, sliding speed, and surface roughness on the friction and wear of high-purity niobium (Nb) during sliding without and with an introduction of water were systematically investigated. Increasing the normal load or sliding speed decreased the friction of the Nb under the both dry and wet conditions because the increased wear of the Nb decreased the interfacial shear strength between the steel ball and Nb by promoting the surface roughening and the production of wear debris. However, the Nb tested at the lowest sliding speed under the lowest normal load with water exhibited the lowest friction and wear due to the formation of oxide layer on the wear track. The friction and wear of the Nb tested under the dry condition decreased with increased surface roughness because the higher interfacial shear strength between the steel ball and smoother Nb resulted in the earlier breakdown of the native oxide layer and direct contact between the steel ball and Nb. However, increasing the surface roughness of the Nb increased its friction and wear under wet conditions, probably due to the easier breakdown of the oxide layer that formed on the rougher surface during sliding. The tribological results clearly showed that the introduction of water during sliding had a significant influence on the tribological properties of the Nb.     

Influence of Sliding Speed on the Tribological Characteristics of Si3N4-hBN Ceramic Materials

The influence of sliding speed on the unlubricated tribological behaviors of silicon nitride–boron nitride (Si₃N₄-hBN) composites was investigated with two modes in air by a pin-on-disc tribometer. Using the upper disc–on–bottom pin test mode, as the sliding speed increased, the friction coefficient of the sliding pairs showed an upward trend; for example, from 0.18 at the sliding speed of 0.40 m/s to 0.54 at the sliding speed of 1.31 m/s for the Si₃N₄/Si₃N₄–20% hBN pair. The surface analysis indicated that a tribochemical film consisting of SiO₂ and H₃BO₃ formed on the wear surfaces of the Si3N4/Si3N4–20% hBN sliding pair at sliding speeds of 0.40 and 0.66 m/s. Moreover, the formation of this film lubricated the wear surfaces. At the sliding speed of 1.31 m/s, no tribochemical film formed on the wear surfaces, most likely due to the increase in surface temperature. In the upper pin–on–bottom disc test mode, the wear mechanism was dominated by abrasive wear, and no tribochemical products could be detected on the wear surfaces. The increase in sliding speed weakened the degree of abrasive wear, leading to a decrease in the friction coefficients.     

M35与GCr15干摩擦磨损性能的研究

在HT-1000型高温摩擦磨损试验机上,对M35高速钢进行干滑动摩擦磨损试验,利用SEM(扫描电镜)观察并分析摩擦面磨损形貌及磨损机理。结果表明,M35高速钢在与GCr15滚动轴承合金钢配副干摩擦条件下,随着速度的增加,摩擦因数先降低后升高,然后再降低。当摩擦热累积达到一定值后,摩擦表面产生严重塑性变形和化学变化,摩擦副表面产生氧化磨损、粘着磨损、磨粒磨损和犁沟磨损,形成转移润滑膜,此时摩擦因数较低,磨损率也相对较低。     

Wear of Unlubricated Steel Surfaces in Sliding Contact

Observations have been made of the wear from an SAE 1113 steel pin specimen rubbing on a SAE 113 steel disk in a normal laboratory atmosphere in relation to normal load (0.5–10.4 lbf), slidinq speed (21–188 ft/sec), sliding distance and track history. As a function of sliding distance, three regions are observed; (i) initial severe wear, (ii) mild wear resultinq from the formation of oxide layers on both the pin specimen and transferred particles adhering to the track, (iii) a milder wear, due to the attainment of a uniform track condition. The wear rate measured in (ii) is observed to be proportional to normal load for constant (normal load)^1/2 × (sliding speed) provided that the magnitude of this parameter is insufficient to cause periodic removal of the surface film. This conclusion is shown to be compatible with earlier theoretical predictions when the presence of an oxide layer was pre-supposed. Unlike the coefficient of friction which is primarily determined by the pin surface condition only, the pin wear rate depends on the conditions of both the pin and track surface.     

青铜-石墨热喷涂层在干摩擦和水润滑条件下的摩擦磨损性能

在MM-200摩擦磨损试验机上研究了青铜-石墨热喷涂层在干摩擦和水润滑条件下的摩擦磨损性能,采用扫描电镜(SEM)对磨损表面形貌进行了观测和采用X射线能谱分析(XPS)分析了涂层成分。结果表明,在水润滑条件下涂层摩擦因数和磨损率均低于干摩擦条件下;在水润滑条件下磨损机制为轻微磨粒磨损和犁削磨损,在干摩擦下主要是较为严重的粘着磨损和犁削。这是由于水润滑降低了摩擦副界面温度,提高了石墨润滑膜的韧性,改善了润滑效果,从而阻止了粘着磨损的发生,水还促进了钢偶件表面致密氧化膜的形成,从而减轻磨损。因此水润滑对涂层磨损性能有较大影响。     

Formation of Cylindrical Sliding-Wear Debris on Silicon in Humid Conditions and Elevated Temperatures

The present study investigates the mechanics of roll formation between sliding bodies at elevated temperatures and humid conditions. Silicon is used as the model material for reciprocating linear sliding tests. The evolution of tribological rolls initially involves the rapid oxidation of silicon wear debris by water, the deformation of SiO₂ particles into platelets, and then the compaction of these particles into a film deposited on the wear surface. The formation of compacted silica film requires minimum adsorption of water which enhances the adhesion between silica platelets. The stress cycle imposed on the film leads to the delamination of platelets near the sliding surface. The delaminated debris cluster into multiple aggregates that are subsequently rolled into dense cylindrical particles so as to relieve the interfacial shear stress. When the film and rolls are formed, the friction and wear rate is maintained at low steady state values.     

Reciprocating sliding wear of 9% Cr steel in carbon dioxide at elevated temperatures

Experiments were conducted on the initial stages of reciprocating sliding wear of a 9% chromium steel in an environment of carbon dioxide at temperatures in the range 200 to 550°C. At ambient temperatures of 290°C and above, an initial severe wear mode was followed by a transition to mild oxidational wear. At any given ambient temperature above 290°C, the distance of sliding required to reach such a transition was found to depend on load and mean sliding speed, although the dependency on speed was not simple. When a transition occurred, most of the surfaces were covered with a stable oxide film which consisted of an agglomerate layer of wear debris being mainly of oxide at the surface and mainly at the metal boundary. This film was supported by a work hardened layer extending for about 30 μm into the bulk of the metal. A surface model is proposed to explain the mechanism of formation of the supportive oxide layer; predictions of volume of material removed and final oxide coverage at the transition are in close agreement with experimental values     

SiCp增强铝基复合材料与Kevlar增强摩擦材料摩擦副摩擦磨损机理研究

采用盘销式摩擦磨损试验机，对SiCp含量为20vol％的铝基复合材料和Kevlar增强摩擦材料组成的摩擦副在于摩擦条件下的摩擦磨损机理进行了实验研究。结果表明：摩擦副在跑合过程中，铝基复合材料中的SiCp颗粒对较软的有机复合材料产生犁削和微观切削效应，磨损机理为铝基复合材料的硬质颗粒对较软的有机复合材料的磨粒磨损；在跑合后的磨损试验中，摩擦材料磨损表面呈现出粘着磨损和塑性变形特征，随着转动速度的增加，塑性流动加剧；摩擦副接触表面发生材料的相互转移，并在铝基复合材料表面形成转移膜，且在较高速度下转移膜更易形成；在高速条件下，摩擦材料表面可见从铝基复合材料的铝合金基体中脱离的SiCp颗粒和熔融迹象；摩擦材料的磨损机理主要为磨粒磨损、粘着磨损和塑性变形。     

腐蚀介质条件下NiCrBSi/WC喷熔层的摩擦学性能研究

采用氧-乙炔火焰喷熔工艺,制备了碳化钨颗粒增强镍基合金喷熔层(NiCrBSi/WC),研究了它在腐蚀介质条件下的摩擦磨损行为与机理,并考察了载荷、滑动速度对其摩擦磨损性能的影响规律。研究结果表明:NiCrBSi/WC具有良好的耐腐蚀磨损性能,且当WC含量为20%时,腐蚀磨损率最低;WC含量超过20%后,由于喷熔层存在“腐蚀原电池”效应,其腐蚀磨损率增大。NiCrBSi/WC的腐蚀磨损率随载荷增加而变大,随速度增大而减小。载荷的增加使喷熔层的犁削磨损加剧,导致摩擦系数和磨损率增大;速度的增大造成摩擦界面温度上升,可生成摩擦转移膜,从而降低了喷熔层的磨损率。     

Wear of metals at high sliding speeds

High speed sliding wear of AISI 1020 steel, AISI 304 stainless steel and commercially pure titanium (75A) was studied using a pin-on-ring geometry. All the tests were carried out in air without any lubricant. The sliding speed was 0.5–10.0 m s^?1 and the normal force was 49.0 N (5 kgf).The friction coefficient of all the materials tested decreased with the sliding speed; this appears to be a consequence of oxide formation. The wear rate of 304 stainless steel increased monotonically with speed, whereas the wear rate of 1020 steel and titanium first decreased and then increased and again decreased, with a maximum occurring at about 5 m s^?1. The complex variation of the wear rate as a function of speed is explained in terms of the dependence of the friction coefficient, hardness and toughness of the materials on temperature. Microscope examinations of the wear track, the sub-surface of worn specimens and the wear particles indicate that the wear mode was predominantly by subsurface deformation, crack nucleation and growth processes, i.e. the delamination process, similar to the low speed sliding wear of metals. Oxidative and adhesion theories proposed in the past to explain the high speed sliding wear of metals are found to be incompatible with the experimental observations.