Sliding wear behavior of Fe-based bulk metallic glass at high temperature

In the past decade Fe-based bulk metallic glasses (BMGs) have attracted increasing attention due to their beneficial properties, including high glass forming ability (GFA), high strength and hardness and high fracture toughness in both fundamental science and engineering application. Most research using these materials has been conducted at room temperature environment, and research that assesses their behavior especially at high temperature has been scarce. We present the results of high temperature effect on the friction and wear behavior of Fe-based bulk metallic glass (BMG), and we tested that this material may satisfy wear and oxidation resistance at high temperature as well as to explore the high temperature wear mechanism of the Fe-based BMG. The dry sliding tribological behaviors of Febased BMG against Si₃N₄ ceramic were conducted with a pin-on-disc friction and wear tribometer. The morphology of the worn surfaces of Fe-based BMG was examined by scanning electron microscopy (SEM) and the chemical composition characterized with energy dispersive spectroscopy (EDS) to observe the wear characteristics and investigate the wear mechanisms. The overall average friction coefficient value generally decreased with increasing temperature, and the glass transition and the formation of protective oxide film played an important role in the tribological behavior of BMG. The wear resistance of Fe-based BMG was not only from their hardness but also from the formation protective oxide layer. Analysis of the worn surface revealed abrasion, plastic deformation and oxidation during sliding test.     

Rolling Friction in a Micro Tribosystem

Pin-on-disc apparatus was used to investigate the effect of temperature on the dry sliding friction characteristics of a Zr-based bulk metallic glass (BMG) near its glass transition temperature (T _g = 625 K) (an analogous phenomenon in crystalline metals called the ductile-brittle transition). Unexpected variation in frictional behavior was observed in the temperature range of 603–643 K, suggesting that the glass transition and formation of protective oxide layers played roles in the tribological properties of BMG. An explanation of the behavior is given based on Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) analysis.     

Cavitation erosion behaviour of Zr-based bulk metallic glasses

The cavitation erosion (CE) behaviour of four Zr-based bulk metallic glasses (BMGs) of general composition Zr–Al–CuNi(Co) was investigated by means of an ultrasonic vibration device and compared with that of S30431 austenitic stainless steel. The results show that the CE resistance of Zr-based BMGs, in terms of incubation time and maximum rate of erosion, is approximately 10 times higher than that of S30431 austenitic stainless steel. It was also found that a small addition of Co (3 at.%) decreases significantly the maximum rate of erosion of the Zr-based BMG investigated. Initial hardness of the Zr-based BMGs was found to be in a good correlation with their maximum cavitation erosion rates.     

Wear Resistance of the La<Subscript>62</Subscript>Cu<Subscript>12</Subscript>Ni<Subscript>12</Subscript>Al<Subscript>14</Subscript> Bulk Metallic Glass Under Dry Friction Conditions

The wear properties of a La₆₂Cu₁₂Ni₁₂Al₁₄ bulk metallic glass (BMG) using sliding wear system under the various normal loads and the annealing conditions have been investigated. Although the La₆₂Cu₁₂Ni₁₂Al₁₄ BMG is brittle during the tensile testing, it exhibits ductile behaviors during the sliding wear process. The SEM and the EDS analyses of the wear tracks and the debris after the sliding wear processes indicate that the wear mechanism is a combination of abrasion, adhesion, and oxidation. It is found that the wear resistance is significantly affected by the normal loads. With the increases in the wear load, the wear loss and the friction coefficient decrease. In addition, it is found that the wear properties are significantly affected by the annealing conditions. Compared with the annealed BMG alloys, the as-cast BMG alloy with a low hardness exhibits good wear resistance, which is attributed to the better ductility during the wear testing.     

Dry Sliding Tribological Properties of Fe-Based Bulk Metallic Glass

The dry or unlubricated sliding friction and wear properties of as-cast and annealed BMG (bulk metallic glass) with nominal composition of Fe_66.7C_7.0Si_3.3B_5.5P_8.7Cr_2.3Al_2.0Mo_4.5 against Si₃N₄ ceramic ball was studied, along with a conventional material, using a ball-on-disk tribotester at room temperature. The overall average coefficient of friction value of the as-cast BMG was in the range of 0.26?C0.42, which was better than the conventional material SUJ2 (0.36?C0.46) and comparable with SUS304 (0.31?C0.40). The wear mechanism of the Fe-based BMG changed with wear condition. The wear rate increased with increasing load. The hardness of the BMG increased during annealing, however, the wear resistance did not increase proportionally.     

激光熔覆合金表面耐磨性试验研究

使用CO2激光器对45#钢表面进行Co基和Ni基合金熔覆处理。利用销盘式摩擦试验机对激光熔覆表面进行摩擦磨损试验,研究干摩擦和润滑条件下磨损机理。Ni合金熔覆层比Co基耐磨性要好。润滑条件下,两种合金的耐磨性比干摩擦都得到很大提高。     

铜包石墨含量对铜锰铝复合材料摩擦磨损性能的影响

为改善铜锰铝合金的烧结性能,并提高其在干摩擦下的摩擦磨损性能,以铜包石墨作为自润滑相加入到铜锰铝合金中,采用等离子真空压力烧结方法制备铜锰铝/石墨复合材料,分析铜包石墨含量对复合材料的密度、硬度的影响,探讨不同复合材料在干摩擦和油润滑条件下的摩擦磨损性能.结果表明:相比真空和氢气还原气氛下的烧结方式,等离子体烧结铜锰铝...     

9SiCr表面激光熔覆合金/20MnSiV磨损性能研究

采用Ni合金和Co合金对9SiCr工具钢表面进行激光熔覆，并将熔覆层与20MnSiV配副在干摩擦和油润滑条件下进行磨损试验。采用扫描电子显微镜对磨损表面形貌进行分析，发现油润滑条件下二者的耐磨性有很大提高，其磨损形式主要是磨粒磨损。Ni合金熔覆层与20MnSiV配副时磨损相对较小。     

铜镍锡合金干滑动磨损行为研究*

大型装备上的铜镍锡合金工件常常工作在润滑不足或者无润滑的工况条件下,因此有必要研究铜镍锡材料在干摩擦下的性能。采用CEF-I型销-盘式磨损试验机对铜镍锡合金在不同载荷与转速条件下进行干滑动摩擦磨损试验,采用扫面电子显微镜、能谱仪和轮廓检测仪对磨损表面进行检测,研究铜镍锡合金的干滑动磨损行为,并探讨其磨损机制。结果表明：在转速一定时,平均摩擦因数随载荷增大总体呈波动下降趋势,铜镍锡合金试件磨损量先缓慢增加,在较高载荷下快速增加;在载荷一定时,平均摩擦因数随转速增大先增大后减小,铜镍锡合金试件磨损量总体呈先减小后增大趋势;随着载荷的增大,铜镍锡合金的磨损机制由轻微黏着和剥层磨损到明显的黏着和剥层磨损,再到严重的黏着和疲劳磨损,随着转速的增大,铜镍锡合金的磨损机制由磨粒磨损转变为黏着磨损再到剥层磨损。在较低载荷下,随着转速的增大,铜镍锡合金摩擦磨损性能保持很好的稳定性,因此铜镍锡合金适用在高转速较低载荷的干摩擦工况下。     

A combined arc-melting and tilt-casting furnace for the manufacture of high-purity bulk metallic glass materials

An arc-melting furnace which includes a tilt-casting facility was designed and built, for the purpose of producing bulk metallic glass specimens. Tilt-casting was chosen because reportedly, in combination with high-purity processing, it produces the best fatigue endurance in Zr-based bulk metallic glasses. Incorporating the alloying and casting facilities in a single piece of equipment reduces the amount of laboratory space and capital investment needed. Eliminating the sample transfer step from the production process also saves time and reduces sample contamination. This is important because the glass forming ability in many alloy systems, such as Zr-based glass-forming alloys, deteriorates rapidly with increasing oxygen content of the specimen. The challenge was to create a versatile instrument, in which high purity conditions can be maintained throughout the process, even when melting alloys with high affinity for oxygen. Therefore, the design provides a high-vacuum chamber to be filled with a low-oxygen inert atmosphere, and takes special care to keep the system hermetically sealed throughout the process. In particular, movements of the arc-melting electrode and sample manipulator arm are accommodated by deformable metal bellows, rather than sliding O-ring seals, and the whole furnace is tilted for tilt-casting. This performance of the furnace is demonstrated by alloying and casting Zr(55)Cu(30)Al(10)Ni(5) directly into rods up to ? 10 mm which are verified to be amorphous by x-ray diffraction and differential scanning calorimetry, and to exhibit locally ductile fracture at liquid nitrogen temperature.     

Wear and Lubrication Behaviors of Cu-Based Friction Pairs with Asperity Contacts: Numerical and Experimental Studies

This paper aims to investigate the wear and lubrication behaviors of wet Cu-based friction pairs. A mixed lubrication model in plane contacts is developed, and the tests of pin-on-disk are carried out. Wear losses are measured by the oil spectrum analysis method. The wear loss, the real contact area ratio, and the load sharing ratio are analyzed. Effects of sliding velocity, temperature, and pressure are considered. The results show that the temperature is the most significant influence on the wear loss of lubricated Cu-based friction pairs. As the temperature rises from 30 to 150 °C, wear loss increases from less than 0.4 mg to about 2.3 mg. The wear factor of the lubricated Cu-based friction pair in asperity contact areas is \(K_{c} = 9.4 \times 10^{ - 9}\) (g/Nm). When the lubricated wear is slight, the oil spectrum analysis method is an effective approach to accurately determine the wear loss.     

Zr55Cu30Al10Ni5块体非晶合金在超声振动场下的流变成形能力

将超声振动场引入到非晶过冷液流变成形中,设计了一套超声振动辅助金属热塑成形实验装置,进行了Zr55Cu30Al10Ni5块体非晶合金高温单轴压缩实验,研究了非晶合金在超声振动辅助下过冷液相区内的流变行为。实验结果表明,超声振动能减小非晶合金的流动应力与黏度,且输入功率越大,越有利于非晶合金的变形。分析了超声振动场提高非晶合金流变成形能力的机理：振动导致变形过程中内应力和摩擦力周期性消失,宏观上则表现为变形抗力的降低和摩擦条件的改善。     

Friction and wear of a Zr-based amorphous metal alloy under dry and lubricated conditions

The unusual internal structure of amorphous metals has been of interest to the tribology community for several decades, but most of the research on these materials has involved unlubricated experiments or tests in other than ambient air environments. If the suitability of amorphous metals is to be evaluated for engineering applications, a great deal more research is needed to assess their behavior under liquid lubricated conditions. Studies in the early 1980s focused on Fe---Co---B---Si compositions. The results reported here focus on an alloy system based on zirconium. Pin-on-disk tests were performed both dry and with diesel oil lubrication. The disks were composed of polished SAE 52 100 steel, and pin specimens of type 303 stainless steel, commercially-pure nickel (Ni-200), and an amorphous alloy of Zr---Cu---Ni---Ti---Al were used. The amorphous alloy was the hardest of the three pin materials. Friction coefficients and wear rates were measured under a limited set of conditions. Under dry conditions, the amorphous metal alloy performed comparably or slightly better than the other two pin materials, but under lubricated conditions, it had the highest friction coefficient and highest wear rate of the three combinations. Differences in the ratios of dry to lubricated wear rates for the three material combinations are discussed in terms of the compatibility of non-ferrous materials with current engine lubricants. Observations on the nature of amorphous alloy wear particles are linked to a combination of simultaneously occurring wear processes. No sliding-induced transformations were detected by X-ray methods.     

Erosion–corrosion behavior of Zr-based bulk metallic glass in saline-sand slurry

Bulk metallic glass (BMG) is supposed to have a good erosion–corrosion (E–C) resistance due to its high hardness and good corrosion resistance. To reveal the E–C behavior, Zr₅₅Cu₃₀Ni₁₀Al₅·BMG is investigated using a slurry pot erosion tester. Experimental results show the volume loss rate of BMG increases with an increase in the particle size, sand concentration or impact velocity. The corrosion current density and the synergism rate increase with the increasing impact velocity. During E–C process, the surface microstructure transforms gradually from pure amorphous to composite mixture of crystalline and amorphous phases. The E–C resistance of BMG is better than that of 304 stainless steel, but not as expected as its high hardness.     

Ultra-High Tribological Performance of Magnetron Sputtered a-C:H Films in Sand-Dust Environment

The hydrogenated amorphous carbon (a-C:H) films were prepared on AISI 440C steel substrates using a RF magnetron sputtering graphite target in the CH₄ and Ar mixture atmosphere. The friction and wear behavior of a-C:H films were comparatively investigated by pin-on-disc tester under dry sliding and simulated sand-dust wear conditions. In addition, the effects of applied load, amount of sand and sand particle sizes on the tribological performance of a-C:H films were systemically studied. Results show that a-C:H films exhibited ultra-high tribological performance with low friction coefficient and ultra-low wear rate under sand-dust environments. It is very interesting to observe that the friction coefficient of a-C:H film under sand-dust conditions was relatively lower when compared with dry sliding condition, and the wear rate under sand-dust conditions kept at the same order of magnitude (×10⁻¹⁹ m³/N m) with the increase of applied load and particle size as a comparison with the dry sliding condition. Based on the formation of “ridge” layer (composite transfer layer), a transfer layer-hardening composite model was established to explain the anti-wear mechanisms and friction-reducing capacity of a-C:H solid lubrication films under sand-dust conditions.     

Evolution of nickel iron-based amorphous alloy structure under friction

The tribological behavior and structural transformations under friction of Ni-Co-Fe-Cr-Mo-Si-B and Ni-Fe-Si-B amorphous alloys obtained by speed hardening from melt are studied. Under unlubricated friction, crystalline layers are shown to arise on the surface of the amorphous alloys. It is concluded that the formation of a crystalline layer on the surface of the amorphous Ni-Fe-Si-B alloy of a specific atomic weight differing from the matrix phase gives rise to high extending stresses. This encourages the accelerated origination and propagation of surface cracks and decreases the alloy’s wear resistance. The amorphous Ni-Co-Fe-Cr-Mo-Si-B alloy, characterized by a higher crystallization temperature, has a higher wear resistance compared to the Ni-Fe-Si-B alloy.     

In-process surface roughness measurement of bulk metallic glass using an adaptive optics system for aberration correction

Bulk metallic glasses (BMGs) have received extensive attention recently due to amorphous-related extraordinary properties such as high strength, elasticity, and excellent corrosion resistance. In particular, Zr-based BMGs are recognized as a biocompatible material and surface roughness may affect many aspects of cell attachment, proliferation and differentiation. Therefore, this study presents an in-process measurement of surface roughness by combining an optical probe of laser-scattering phenomena and adaptive optics (AO) for aberration correction. Measurement results of six Zr-based BMGs samples with a roughness ranging from 0.06 to 0.98 μm demonstrate excellent correlation between the peak power and average roughness with a determination coefficient (R²) of 0.9974. The proposed adaptive-optics-assisted (AO-assisted) system is in good agreement with the stylus method, and less than 8.42% error values are obtained for average sample roughness in the range of 0.05–0.58 μm. The proposed system can be used as a rapid in-process roughness monitor/estimator to further increase the precision and stability of manufacturing processes for all classes of BMGs materials in situ.     

The effect of silicon content and morphology on the wear of aluminium-silicon alloys under dry and lubricated sliding conditions

Improvement in the efficiency of the internal combustion engine has resulted in the increased usage of aluminium alloys and, in particular, aluminium-silicon as a substitute for cast iron. Despite the wide use of such materials in tribological environments little knowledge is available on the wear resistance of aluminium-silicon alloys. This paper investigates the wear performance of a range of binary aluminium-silicon alloys produced by a novel melt-spray technique. In addition, samples of the 11wt% silicon alloy were produced by conventional casting methods to elucidate the influence of silicon morphology on wear resistance. Pin-on-ring wear tests were carried out under dry and boundary-lubricated conditions. Surface analysis showed a similar wear mechanism under both conditions, these being: (1) oxidative and (2) metallic wear. Under boundary-lubricated conditions the load at which the transition to metallic wear occurred was increased. Raising the silicon content of the alloy was reflected in an increase in both wear resistance and transition load. Under dry sliding conditions the wear rate of the 11wt% alloy increased with a reduction in the silicon particle size, whereas under boundary-lubricated conditions the reverse was observed and the sand-cast alloy exhibited superior performance.     

Tribological Properties of MoS2 with Different Morphologies in High-Density Polyethylene

The tribological properties of high-density polyethylene (HDPE) modified by MoS₂ with different morphologies (nano-spheres, nano-platelets, and micro-platelets) were investigated using an end-face tribometer under dry friction and rapeseed oil lubrication. Under dry friction, MoS₂ nano-platelets and nano-spheres exhibited their best properties at 1.0 and 1.5?% (wt%) MoS₂ content, respectively. Under oil lubrication, the nano-spheres were better additives in HDPE than the other two. The melting of HDPE was the main wear mechanism under dry friction, whereas abrasive is the main wear mechanism under oil lubrication. The changing wear mechanisms led to anti-wear variations in HDPEs with increasing MoS₂ contents. The tribological properties were closely related to the crystallinity and thermo-mechanical properties of MoS₂/HDPE. The samples with lower damping factors and better crystallinity showed better tribological properties. The excellent anti-wear properties of nano-spheres can be attributed to the deformation and exfoliation of nano-spheres in the friction process. Nano-platelets and nano-spheres in HDPE are advantageous under dry friction and oil lubrication, respectively. This study better elucidated the relationship between the property and morphology of MoS₂ in a polymer.     

Mild Sliding Wear of Fe–0.2%C,Ti–6%Al–4%V and Al-7072: A Comparative Study

The mild sliding wear of Fe–0.2%C, Ti–6%Al–4%V and Al-7072 was investigated by means of pin-on-disc sliding tests. The applied pressure was 1 MPa and the sliding velocity was varied between 0.2 and 1 m/s. The sliding behaviour was followed by continuous measurements of the friction coefficient, pin wear and pin temperature. For the Fe alloy, wear was mixed (delamination and oxidation), and friction and wear coefficients were found to decrease with sliding velocity. The Al and Ti alloys displayed a different behaviour, characterised by the occurrence of sliding distance transitions at 0.8 and 1 m/s for the Al alloy, and at 0.4 up to 1 m/s for the Ti alloy. Before the transition, the wear coefficient of the Al alloy was very low, because of the presence of a compacted tribolayer on the sliding surface. After the transition wear was by delamination: the wear rate increased but the friction coefficient decreased. For the Ti alloy, wear occurred by oxidation and was quite high before the transition. After the transition, both the wear rate and the friction coefficient decreased, although the wear process became unstable with repeated oscillations in the friction coefficient. The results allowed us to highlight the role of flash temperature in determining the wear mechanisms of the alloys under study and the necessity of properly considering the sliding distance transitions to make reliable comparisons and obtain guidelines for safe operations.