Tribological Behavior of Ti3AlC2 Against SiC at Ambient and Elevated Temperatures

In this paper, we reported the tribological behavior of Ti₃AlC₂ disk sliding against SiC ball from room temperature (RT) to 1,000 °C. The tribological properties are highly dependent of testing temperature. At RT, the coefficient of friction (CoF) is as low as 0.34 in the steady state, but the wear rate is relative high (4.26 × 10^?4 mm³/Nm). At 200 and 400 °C, the CoF is as high as 1.21, and the wear rates are very high, about on the order of 10^?3 mm³/Nm. From 600 to 1,000 °C, however, Ti₃AlC₂ exhibits quite low wear rate on the order of 10^?6 mm³/Nm and relative moderate CoF, 0.60–0.80. The compacted continuous oxide layer at 600 °C and above might be responsible for the outstanding wear resistance.     

Dry-Sliding Tribological Properties of TiAl/Ti2AlC Composites

The microstructure, mechanical and dry-sliding tribological properties of TiAl-based composites with 20 and 40 vol% in situ formed Ti₂AlC, produced by hot press sintering process, are investigated. The microstructural characterization reveals that Ti₂AlC phase is in the form of spherical particles and large blocks, and the quantity of the blocks increases with Ti₂AlC content. This difference in the morphology and distribution of the Ti₂AlC phase leads to the discrepancy of the wear resistance of the composites. In contrast to the Ti-46Al-2Cr-2Nb intermetallics, the dry-sliding wear resistance of the TiAl/Ti₂AlC composites first declines slightly and then enhances with the Ti₂AlC content. Furthermore, the TiAl/40 % Ti₂AlC composite shows low wear rate at higher sliding speed.     

Tribological Behavior and Tribochemistry of Self-mated Ti3SiC2 in Ethanol

The tribological behavior of self-mated Ti₃SiC₂ in low viscosity fluids, that is, water and ethanol, is investigated. The results show that both water and ethanol effectively reduce the friction and wear of self-mated Ti₃SiC₂. The friction coefficient and total wear rates of Ti₃SiC₂ tribo-pair are 0.82 and 2.17 × 10^?2 mm³/N m under dry condition, 0.41 and 6.50 × 10^?4 mm³/N m in water and 0.16 and 2.22 × 10^?4 mm³/N m in ethanol. As sliding distance is prolonged from 0.5 to 22.9 km, the total wear rates of Ti₃SiC₂ in ethanol can be further reduced. Mechanical wear of Ti₃SiC₂ is partly inhibited in water and greatly inhibited in ethanol. Surface polishing of Ti₃SiC₂ pin and tribochemistry are the two distinct characteristics of self-mated Ti₃SiC₂ in ethanol. The surface film in ethanol is composed of TiO₂ and SiO. Tribo-products in ethanol, that is, silica gel and titanium dioxide, are found. Polycondensation of ethanol by the catalysis of TiO₂ and SiO_2?x gives birth to paraffins and olefins.     

Reciprocating friction and wear behavior of Ti3AlC2 and Ti3AlC2/Al2O3 composites against AISI52100 bearing steel

In this work, the dry sliding friction and wear properties of Ti₃AlC₂ and Ti₃AlC₂/Al₂O₃ composites against AISI52100 steel ball were investigated using a reciprocating ball on flat configuration under different normal loads. The results indicated that the friction/wear processes of both Ti₃AlC₂ and the composites against AISI52100 steel experienced two different stages with an abrupt transition between them under all test conditions. The first stage was characterized by low coefficient of friction (μ) and neglectable wear rate. While the second stage was of much higher wear rate and μ. When the transition occurred, μ increased dramatically accompanied with formation of a mass of debris. In Ti₃AlC₂, the main wear mechanisms during the first stage involved surface materials transfer and oxidation accompanied with subsurface damages by grains kinking, delamination as well as transgranular and intergranular cracks. Accumulating of such contact damages under repeated sliding contact finally leaded to surface and subsurface microfracture of Ti₃AlC₂. Then microfracture controlled severe wear started. Incorporation of Al₂O₃ in Ti₃AlC₂ not only improved wear resistance of Ti₃AlC₂ but also extended the first mild friction/wear stage, because Al₂O₃ particles borne load and restrained large-scale deformation and microfracture of Ti₃AlC_2.     

球磨参数对燃烧合成Ti3AlC2金属陶瓷的影响

以Ti、A1和C粉末为原料,研究了球磨转速、球料比对燃烧合成Ti3AlC2的影响。研究结果表明,不同的球磨转速、球料比对Ti—Al—C体系燃烧合成Ti3AlC2金属陶瓷组织、结构有较大影响。球磨转速较高时,混合粉料具有更高的活化能,并完全参与反应生成Ti3AlC2。适当的球料比可有效减小粉末粒度,有助于燃烧合成出片层结构更为细小的Ti3AlC2金属陶瓷。     

Intrinsic self-lubricity of layered Ti3AlC2 under certain vacuum environment

In this study, we report that a layered Ti₃AlC₂ ceramic exhibited three distinct tribological behaviors at different vacuum degrees. It is firstly found that the layered Ti₃AlC₂ exhibited intrinsic self-lubricity under vacuum degree from 2.0×10⁴ to 5 Pa with the coefficient of friction (CoF) as low as 0.2 and nearly no wear. Under lower 0.1 Pa and air atmosphere, however, it showed lubrication failure. Under lower 0.1 Pa, The CoF abruptly rose after transitory low friction in initial duration and deteriorated wear occurred in the Ti₃AlC₂. The CoF sluggishly ascended to stable value from 0.2 to 0.7 in air. The lubricating mechanism of Ti₃AlC₂ ceramic was proposed.     

Effect of Ag and Ti3SiC2 on Tribological Properties of TiAl Matrix Self-lubricating Composites at Room and Increased Temperatures

Dry sliding tribological properties of TiAl matrix self-lubricating composites (TMSC) containing Ag, Ti₃SiC₂, Ag and Ti₃SiC₂ were investigated from 25 to 800 °C under ball-on-disk test conditions against Si₃N₄ counterface under the same conditions of 10 N-0.234 m/s. The results indicated that the tribological properties were strongly dependent on the lubricant additives. TMSC with the addition of Ag and Ti₃SiC₂ (TAT) exhibited the lower friction coefficients (0.32–0.43) and less wear rates (1.23–4.13 × 10^?4 mm³ N^?1m^?1) in the wide temperature range of 25–800 °C. The excellent tribological properties of TAT over the wide temperature range were attributed to the synergetic effect of Ag and Ti₃SiC₂ lubricants, silver diffusion forming a rich-silver smooth tribo-film on the frictional surface of TAT at low and moderate temperatures from 25 to 400 °C, while Ti₃SiC₂ oxidation reaction forming rich-oxide tribo-film on the worn surface of TAT at higher temperatures of 600 and 800 °C.     

SHS/PHIP法制备的Ti3AlC2陶瓷的可加工性

研究了用SHS/PHIP技术制备的Ti3AlC2层状陶瓷的可加工性及其机理。结果表明,Ti3AlC2陶瓷具有自润滑结构、室温显微塑性以及高电导率,用普通高速钢刀具即可进行切削加工,也可采用电火花等特种加工方式进行机械加工。     

Tribological Behavior of Self-mated Ti3SiC2 in Short-Chain n-Alcohols,Glycol and Glycerol under Boundary Lubrication

The tribological behavior of self-mated Ti₃SiC₂ in bath of alcohols are investigated at sliding velocity ranging from 0.005 to 0.3 m/s. The results show that the friction coefficient and wear rates of self-mated Ti₃SiC₂ are reduced greatly under lubrication of alcohols compared to that under dry condition. In alcohols, smooth worn surfaces of Ti₃SiC₂ can be obtained. The mechanical wear is inhibited and the oxidized Ti and Si species on the worn surface are TiO₂ and silica gel. The friction coefficients decrease with carbon numbers and sliding velocity in the n-alcohols. The friction coefficient decrease with sliding velocity in glycol and glycerol as well. The decrease is determined by the increase of the viscosity of alcohols. In glycerol, at 0.1 m/s and 5 N, the friction coefficient of self-mated Ti₃SiC₂ is 0.08 which is the lowest in this paper. The lubrication regimes are calculated according to classical lubrication theory. At velocity from 0.005 to 0.3 m/s, in all of the alcohols except glycerol, the λ are below 1 which indicates that the lubrication regime is BL. While in glycerol, the lubrication regimes vary from BL to BL and EHL, then to EHL as the velocity increases.     

Tribological Behavior of Novel Ti3SiC2 (Natural Nanolaminates)-Reinforced Epoxy Composites during Dry Sliding

In this article, we report for the first time the synthesis and characterization of Ti₃SiC₂–epoxy (MAXPOL) composites. Three novel composites were designed by adding 20.7, 30.6, and 71.6 vol% Ti₃SiC₂ particulates to an epoxy matrix. The microstructure evaluation by scanning electron microscopy (SEM) showed that the Ti₃SiC₂ particles are well dispersed in the epoxy matrix. The addition of Ti₃SiC₂ enhanced the ultimate yield strength (UYS) and hardness of all of the composites compared to epoxy. Tribological studies were performed by a tab-on-disc method against Inconel 718 and alumina substrates. In both cases, the mean friction coefficient (µ_mean) decreased as the concentration of Ti₃SiC₂ in the epoxy matrix was increased. The concomitant wear rates (WRs) also decreased steadily and then increased slightly after reaching a concentration of ~32.6 vol% Ti₃SiC₂. The tribological studies proved conclusively that the addition of Ti₃SiC₂ in the epoxy matrix imparts self-lubricity to the composites. The tribofilms formed on different tribosurfaces were also characterized by detailed SEM investigations.     

载荷对丁腈橡胶摩擦学特性的影响

采用栓－盘式摩擦磨损试验机考察了载荷对丁腈橡胶摩擦学特性的影响,分析了其作用机理,结果表明,丁腈橡胶的摩擦系数和磨损均随损均随载荷的增加而降低;在较低载荷时,丁腈橡胶表现为滞后摩擦,在较高载荷时,表现为粘着摩擦,在较低的滑动速度下,载荷的改变不会引起丁腈橡胶摩擦过程中摩擦化学反应的发生,只是产生简单的分子机械断裂。     

Effect of Atmosphere and Temperature on the Tribological Behavior of the Ti Containing MoS<Subscript>2</Subscript> Coatings Against Aluminum

MoS₂ coatings exhibit low coefficient of friction (COF) when sliding against aluminum; however, the magnitudes of their COF show high sensitivity to environmental conditions. Ti could reduce the sensitivity of the frictional behavior of MoS₂ coatings to moisture. This study examines the tribological properties of Ti containing MoS₂ coating (Ti–MoS₂) tested against an aluminum alloy (Al-6.5% Si) in ambient air (58% relative humidity, RH), dry oxygen, dry air and dry N₂ (< 4% RH) atmospheres. The Ti–MoS₂ coating exhibited similar COF values under an ambient (0.14), dry oxygen (0.15) and dry air (0.16) atmospheres. It was found that oxidation of MoS₂ to MoO₃ was responsible for high COF under these testing conditions as revealed by Energy-dispersive X-ray Spectroscopy (EDS) and micro-Raman spectroscopy. However, a low and stable COF of 0.07 was observed under a dry N₂ condition. This work further showed that the tests performed at elevated temperatures, up to 400 °C in a dry N₂ atmosphere sustained the low and stable COF of the Ti–MoS₂ coatings. The sliding tests performed under a dry N₂ atmosphere prevented the formation of MoO₃ and as a result, the Ti–MoS₂ coatings maintained low COF values. Low COF values were also attributed to the formation of MoS₂ transfer layers.     

Tribological Properties of TiAl Matrix Self-Lubricating Composites Containing Multilayer Graphene and Ti3SiC2 at High Temperatures

An investigation is conducted on the unexplored synergistic effects of multilayer graphene (MLG) and Ti₃SiC₂ in self-lubricating composites for use in high-temperature friction and wear applications. The tribological properties of TiAl matrix self-lubricating composites with different solid lubricant additions (Ti₃SiC₂-MLG, MLG) are investigated from room temperature to 800°C using a rotating ball-on-disk configuration. Tribological results suggest the evolution of lubrication properties of MLG and the excellent synergistic lubricating effect of MLG and Ti₃SiC₂ as the testing temperature changes. It can be deduced that MLG has great potential applications as a promising high-temperature solid lubricant within 400°C, and a combination of MLG and Ti₃SiC₂ is an effective way to achieve and maintain desired tribological properties over a wide temperature range.     

Tribological Behavior of Ti3Al2.5V Alloy Sliding against EN-31 Steel under Dry Condition

This article aims to study the friction and wear behavior of Ti3Al2.5V alloy sliding against EN-31 steel under dry condition using a multi-tribotester. The effect of variation in load and sliding velocity on wear rate, average coefficient of friction, and contact temperature has been studied and analysis of wear debris has been carried out. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were employed to study the morphology of the wear tracks and deduce microchemical information at the elemental level of worn samples, respectively. Results reveal that the wear rate of Ti-3Al-2.5V increases with increasing sliding velocity and increasing normal load with few exceptions. The average coefficient of friction decreases as the normal load increases with exceptions at some loads. SEM micrographs of worn samples obtained at different loads and sliding velocities show the formation of wear tracks on the surface due to ploughing and flaking of the matrix. The main mechanism responsible for wear of Ti3Al2.5V alloy sample is rupture of the matrix and abrasion. Wear debris analysis shows irregular-shaped wear particles with very sharp edges that appeared to be plastically deformed at high sliding velocity, whereas the wear debris is very loose and fine at lowest sliding velocity.     

电流对铬青铜/紫铜摩擦学特性的影响

采用自制的销盘摩擦磨损试验机,在载流条件下对铬青铜QCr0.5/T2铜的摩擦学特性进行了研究,结果表明电流对摩擦因数和磨损率具有显著影响,电流越大,磨损率越高,摩擦副磨损越严重,摩擦因数越大。载流条件下,摩擦表面发生电点蚀,并出现局部熔化和雨滴状金属颗粒。     

Effect of ZrO2 Nanoparticles Additive on the Tribological Behavior of Multialkylated Cyclopentanes

Monodisperse ZrO₂ nanoparticles with a particle size of about 6–7 nm and low volatile multialkylated cyclopentanes (MACs) lubricant were prepared and characterized. The effect of ZrO₂ nanoparticles as additive on the friction and wear behavior of MACs base oil was investigated. The friction and wear performance of 2 wt% ZrO₂ nanoparticles + MACs was evaluated using an Optimal SRV oscillating friction and wear tester, with a steel ball sliding against the same steel counterpart disc. Results indicate that the wear resistance and load-carrying capacity of MACs base oil were markedly raised and its friction coefficient changed little when 2 wt% ZrO₂ nanoparticles were added to it.     

Optimization and Effect of Weight Fraction of MoS2 on the Tribological Behavior of Mg-TiC-MoS2 Hybrid Composites

This investigation studies the dry sliding wear behavior of magnesium (Mg) matrix composites reinforced with titanium carbide (TiC) and molybdenum disulfide (MoS₂) fabricated using a powder metallurgy technique. The effects of both TiC (0–10%) and MoS₂ (0–10%) content on the tribological properties are investigated. Wear tests are carried on magnesium reinforced with TiC and MoS₂ individually and together in different proportions, using a pin-on-disc apparatus under dry sliding condition. The experiments were made using a Taguchi L₂₇ orthogonal array with five factors at three levels. The wear resistance of the developed composites improved significantly compared to that of the magnesium matrix due to the effect offered by both reinforcements. Analysis of variance was used to verify the significance of factors influencing wear. In addition, the worn surfaces of the wear-tested specimens were examined using a scanning electron microscope coupled with energy-dispersive spectroscopy.     

Effect of Carbon Nanotube Addition on Tribological Behavior of UHMWPE

Carbon nanotubes (CNTs) were added to Ultra-high molecular weight polyethylene (UHMWPE) to improve the tribological properties of UHMWPE. CNTs which have a diameter of about 10–50 nm, while their length is about 3–5 nm were produced by the catalytic decomposition of acetylene gas using a tube furnace. Ball-on-disc-type wear tests were performed to evaluate the tribological performance of UHMWPE composites reinforced with CNTs. The results showed that addition of carbon nanotube up to 0.5 wt% lowered wear loss significantly and increased friction coefficient slightly. Also through the scanning electron microscope (SEM), the surfaces of UHMWPE were observed and analyzed to discuss the tribological behavior of CNT added UHMWPE.     

The Effect of Temperature on the Tribological Behavior of RBD Palm Stearin

The wide use of petroleum-based oils raises concerns with regard to pollution, and the rising of awareness of greenhouse gases has created a demand for the use of environmentally friendly and biodegradable lubricants for industrial applications. Vegetable oils are one of the bio-oils that have been promoted as a replacement for petroleum products, in part due to their environmentally friendly characteristics; they are nontoxic, biodegradable, and easy to dispose of. Many researchers have performed studies on sunflower oil, corn oil, and soy oil, but few have studied palm oil as a lubricant. Palm oil produced in a high-throughput manner could fulfill the demand for bio-based lubricants. In this study, the influence of temperature on friction and wear performance for refined, bleached, and deodorized (RBD) palm stearin and additive-free paraffinic mineral oil is presented. The experiments were conducted using a four-ball tribotester. Test temperatures of 55, 65, 75, and 85°C were used. The sliding speeds were set to 1,200 rpm. Experiments were run for 1 h under a 392.4 N load. The results of RBD palm stearin were compared with those of paraffinic mineral oil. The experimental results showed that the RBD palm stearin had better performance compared to paraffinic mineral oil in terms of reducing frictional constraints.     

辉光离子渗氮对Ti6Al4V合金在航空煤油中摩擦学性能的影响

为改善钛合金在航空煤油中的摩擦学性能,采用辉光离子渗氮技术对Ti6Al4V钛合金表面进行改性处理。分析了渗氮层的表面形态、组织结构、显微硬度沿层深的分布,对比研究了钛合金基体、渗氮层和5CrMnMo工具钢在航空煤油中分别与GCr15钢及QSn4-3铜合金配副对磨时的耐磨性能,并探讨了渗氮层的表面粗糙度对摩擦磨损行为的影响。结果表明:Ti6Al4V钛合金表面渗氮层硬度明显高于5CrMnMo工具钢,经表面抛光后处理,其耐磨性能显著优于钛合金基材与5CrMnMo工具钢,同时也有效降低了摩擦配副的表面磨损。研究同时发现QSn4-3铜合金配副的磨损体积损失与渗氮层的表面粗糙度呈线性递增关系,原因归于铜合金配副的磨损失效由渗氮层表面微凸体的磨粒磨损作用及航空煤油的润滑状况决定。