Tribological Performance of Boronized,Nitrided, and Normalized AISI 4140 Steel against Hydrogenated Diamond-Like Carbon-Coated AISI D2 Steel

In the current work, AISI 4140 steel was pack-boronized at 950°C for 3 h and gas-nitrided at 550°C for 72 h. All specimens used in this work were prepared from the same steel bar. A 3-µm-thick diamond-like carbon (DLC) coating (a-C:H) was deposited on the AISI D2 high-carbon, high-chromium, cold-worked tool steel by a plasma-assisted chemical vapor deposition technique. Normalized, boronized, and nitrided steel pins were tested against DLC-coated AISI D2 steel at various normal loads (15, 30, 60, and 80 N) for 1,000 and 3,000 m sliding distance in ambient air. Specific wear rate of all pins decreased with increasing load, and a similar trend was observed for the coefficient of friction (COF). Microscopic and energy-dispersive spectroscopic (EDS) analysis confirmed the role of the transfer layer for a low COF with increasing load. At all loads, the specific wear rate of boronized pins was lower than that of the nitrided and normalized pin specimens. Boronized pins showed a specific wear rate in the range of 0.27 × 10^?8 to 0.44 × 10^?8 mm³/Nm and the COF was about 0.1.     

Tribological Behaviors of 52100 Steel in Carbon Dioxide Atmosphere

The tribological behavior of 52100 steel in a carbon dioxide (CO₂) atmosphere was investigated using a reciprocating ball-on-disk tribometer. X-ray photoelectron spectroscopy (XPS) was used to identify the adsorbed surface layers and tribochemical products. We found that CO₂can substantially reduce friction and wear of the steel. Adsorbed and reacted surface layers containing iron carbonate and/or bicarbonate play an important role in reducing friction. A disk, exposed once to CO₂atmosphere, also shows a low friction for a long time even in a vacuum environment. An optimum CO₂pressure exists for effectively reducing friction and wear. A low-pressure CO₂atmosphere is insufficient to produce iron carbonate. In contrast, high pressure engenders serious chemical wear.     

Relating Molecular Structure to Tribological Chemistry: Borate Esters on Copper

The surface and tribological chemistry of 2-propanol and borate esters, isopropoxy tetramethyl dioxaborolane (ITDB), and tetramethyl dioxaborolane (TDB) as gas-phase lubricants for copper surfaces are compared by measuring the friction coefficient and contact resistance in an ultrahigh vacuum tribometer. 2-propanol reacts on copper below room temperature to desorb primarily acetone and causes no friction reduction when used as a gas-phase lubricant. TDB decomposes to deposit BO_x species on the surface and produces an initial decrease in friction coefficient that is not sustained. ITDB, which reacts at room temperature to form a tetramethyl dioxaborolide species on the surface, results in an immediate and sustained decrease in friction coefficient when used as a gas-phase lubricant for copper. This indicates that the surface chemistry of the borate esters can be correlated with their tribological properties and illustrates the effect of replacing a hydrogen atom in TDB with a 2-propoxy group in ITDB on both the surface and tribological chemistry. Analysis of the species formed in the wear track after lubrication with ITDB reveals the presence of graphitic or diamond-like carbon and oxygen, and these elements are also found in the subsurface region of the sample. Rubbing the sample in vacuo after reacting with ITDB shows the removal of a boundary film where the coefficient remains constant and the subsequent removal of the subsurface layer in which the contact resistance rises to its original value.     

Boundary Tribological Behaviors of Untreated and Surface-Modified M50 Steel Lubricated by Fuel JP-10

To explore the possibility of using advanced surface engineering techniques (ASETs) to solve the wear problems caused by the poor lubricity of pure, low-viscosity aviation fuel JP-10, polished M50 bearing steel sample surfaces were treated with nitrogen ion implantation, TiAlN coating deposition, and Ta coating deposition followed by high current pulsed electron beam (HCPEB) irradiation, respectively. Boundary tribological behaviors of these ASET-treated and untreated steel samples sliding in pure JP-10 against a Si₃N₄ ball (ball-on-disc model) were investigated under 2.0 GPa in the atmosphere and the friction tests indicated that significant, reductions, although to different extents, in friction and wear were achieved by these modified surfaces. Simultaneously considering the tribological performance and potential pollution caused by wear debris to JP-10, HCPEB-treated Ta coating with a lowest average friction coefficient of 0.11 and a specific wear rate of around zero was the fittest to offset the inadequate lubricity of JP-10 itself under the laboratory condition.     

Antiwear Tribofilm Formation on Steel Surfaces Lubricated With Gear Oil Containing Borate,Phosphorus, and Sulfur Additives

The formation of antiwear tribofilms plays a critical role in the longevity of automotive gears. The focus of this experimental study was on the lubrication efficacy of gear oils with different contents of borate-, phosphorus-, and sulfur-containing additives leading to the formation of protective tribofilms. Experiments were performed with AISI 52100 steel balls sliding against AISI 52100 steel disks in baths of different oils at ambient (～32 °C) and elevated (～100 °C) temperatures under load and speed conditions favoring sliding in the boundary lubrication regime. Friction coefficient responses accompanied by electrical contact voltage measurements provided real-time information about the formation and durability of the antiwear tribofilms. The wear resistance of the tribochemical films was quantified by wear rate data obtained from surface profilometry measurements of wear tracks on the disk specimens and sliding tests performed at ambient temperatures after the formation of the tribofilms during elevated-temperature sliding. Results indicate a strong dependence of tribofilm formation on temperature and type of additives. The slightly lower friction and higher wear resistance obtained at elevated temperatures with blended oils is attributed to the increased chemical reactivity of additives containing borate, phosphorus, and sulfur, leading to the formation of durable tribofilms. Relatively higher wear resistance and faster tribofilm formation were obtained with the borate-enriched gear oil formulations.     

工艺条件对类金刚石薄膜在不同介质环境下摩擦学性能的影响研究

考察了基底负偏压对类金刚石薄膜(DLC)在无水和有水环境下摩擦性能的影响。利用电子回旋共振等离子体化学气相方法沉积制备DLC薄膜,利用激光拉曼(Raman)、原子力显微镜(AFM)和纳米硬度计表征了其结构特征,用UMT型多功能摩擦磨损实验机考察了其摩擦性能,并用光学显微镜分析了磨痕特征。结果表明:随着基底偏压的增加,表面粗糙度减小;在无水条件下,基底偏压较低的DLC薄膜摩擦因数较高,并存在一定的波动性,基底偏压较高时,摩擦因数较低。在有水条件下,基底偏压对摩擦因数影响不大。总体来说,加水后薄膜磨损较为严重。     

Tribological Properties of Diamond-Like Carbon Films in Low and High Moist Air

Diamond-like carbon (DLC) film was deposited on Si wafer by a plasma CVD deposition system using benzene. Tribological properties of the DLC film were evaluated using a ball-on-disk tribo-meter in low (RH 1720 %) and high humidity (RH 9095 %) conditions in air. The effect of sliding speed (4.2 mm/s to 25 mm/s) and load (1.06 N to 3.08 N) on friction and wear was investigated. The friction behavior of the DLC film was obviously different in low and high humidity. When tested under low humidity conditions, the friction coefficient decreased significantly with increasing speed, and increased with load. However, under high humidity conditions, the friction coefficient increased with the speed and decreased with increasing load. The wear of the DLC film was little influenced by the sliding speed, normal load and humidity; a level of 10^-8 mm³/Nm could be obtained in all tests. The formation of a uniform transfer layer would be the main factor which controlled the friction coefficient of the DLC films. Unlike the friction, the wear resistance of the DLC film is not so easy to discuss and may be affected mainly by the tribo-chemical reaction in all the test conditions.     

Traction of Lubricated Rolling Contacts between Thin-Film Coatings and Steel

Tribological thin-film coatings can enhance the performance of mechanical components such as bearings and gears. Although a lubricant is present in most applications, the interactions of the lubricant with the coated surfaces are not always well understood. In the present study, Stribeck curves (i.e., traction coefficient vs. dimensionless film thickness λ) were generated for lubricated rolling contact between coated and uncoated surfaces. Chromium nitride, tungsten carbide–reinforced amorphous hydrocarbon, and silicon-incorporated diamond-like carbon coatings were evaluated. Compositions, hydrogen concentrations, Raman spectra, and surface energies are reported for the films. A ball-on-flat test configuration was used in 5%, 50%, and 100% slide-to-roll conditions. The test lubricant was a polyalphaolefin containing rust and oxidation inhibitor additives only. Differences in traction performance were observed for different coating types. Traction coefficients decreased at high λ with increased hydrocarbon content in the coating. Coating micro-texture and composition were believed to influence traction as λ became small.     

新型含氮、硫杂环有机硼酸酯在菜籽油中的摩擦学性能研究

从分子设计的观点出发,合成了一种新型含氮、硫杂环有机硼酸酯润滑油添加剂2-硫酮苯并噻唑啉-3-甲基二异辛基硼酸酯（ITTB）。采用四球摩擦磨损试验机评价了其摩擦学性能。结果表明：在菜籽油（RO）中加入添加剂以后,其承载能力明显提高,磨斑直径和摩擦因数均显著降低。从磨斑表面SEM,XPS分析结果可以推断,添加剂在摩擦过程中发生了摩擦化学降解反应,硫元素在钢球的表面形成了一层含Fe2（SO4）3和FeS2的反应膜,氮、硼元素则以吸附膜的形式存在于摩擦表面,2种膜的共同作用提高了菜籽油的减摩抗磨性能及承载能力。     

Tribological Mechanisms of Steels with Respect to Diamond-Like Carbon in Terms of Energy Input

The wear behavior of a carbon steel (SUJ2, ASTM E52100 or similar) and a stainless steel (SUS440C, ASTM 440C or similar) with respect to diamond-like carbon (DLC) was evaluated based on the energy input. The conventional wear equation (Holm-Archard equation) was derived based on the friction force. The wear–energy equation was transformed from the Holm-Archard equation. The measurement method of the energy input induced by a tribometer is proposed, and the equation describing the relationship between the friction coefficient and energy input is introduced. The tribology functions derived from the energy equations are proposed. The wear behavior of the steel balls against the DLC is discussed in terms of tribology functions.     

硫化亚铁固体润滑涂层的制备方法与摩擦学性能研究

描述了硫化亚铁固体润滑涂层的制备方法及摩擦学性能。结果表明,不同方法得到的硫化亚铁涂层都能具有优良的减摩、耐磨、抗擦伤性能,但其摩擦学性能有差异,适用工况条件也不同。并指出了制备方法中存在的缺陷,对其今后的发展作了展望。     

Tribological Behavior of Nickel-Doped Diamond-Like Carbon Thin Films Prepared on Silicon Substrates via Magnetron Sputtering Deposition

In this study, nickel-doped diamond-like carbon (Ni-DLC) thin films were deposited on silicon (Si) substrates using a magnetron cosputtering system by varying DC power density applied to a Ni target at a fixed DC power density applied to a carbon (C) target. Their tribological properties were systematically investigated using a ball-on-disc microtribometer. The tribological results showed that increasing the DC power density applied to the Ni target more than 0.49 W/cm² significantly increased the friction and wear of the Ni-DLC films due to the degraded sp³-bonded cross-linking structures of the films. However, the much lower friction and wear of the Ni-DLC-coated Si samples than those of the uncoated Si sample implied that the Ni-DLC films could effectively prevent their Si substrates from wear. It could be concluded that the Ni-DLC films could be used as high wear-resistant coatings for micromold applications because their tribological properties were significantly influenced by the DC power density applied to the Ni target.     

Tribological Behavior of Patterned PVD TiN Coatings on M2 Steel

A series of lubricated pin-on-disk wear experiments were performed to investigate the tribological behaviors of in-line (IN) and staggered (ST) patterned PVD TiN coatings as well as a fully TiN-coated (FC) coating on M2 steel against ASSAB 17 tool steel mating pins. The influence of applied load on the tribological behavior of the individual types of coating was also investigated. The experimental results showed that the tribological behavior of the two patterns and the FC M2 steel sliding against tool steel was a function of applied load. The wear resistance for any PVD TiN coating pattern was relatively higher at the specific individual loadings of 394, 800, 900 and 1100 N for 4 h under wet lubrication. Wear loss of the two types of patterned discs and pins was lower than that of the full coating counterpart. Wear mechanisms are suggested.     

The Effects of Magnetic Treatment on the Tribological Behavior of AISI 1045 Steel under Lubricated Conditions

The mechanical and tribological properties of pulse-magnetized and untreated AISI 1045 steel were studied comparatively. The microhardness and microstructures of treated and untreated steel samples were analyzed to evaluate magnetic treatment effects on the mechanical properties. Dislocation densities were calculated from X-ray diffraction data according to the Williamson-Hall method. Tribological tests were conducted using a ball-on-disk reciprocating friction and wear tester. Scanning electron and energy-dispersive microscopies were used to analyze the morphologies and elements of worn surfaces. Dislocation densities of AISI 1045 steel were found to increase by 16.5% after magnetic treatment. Treated steel performed better under polyalphaolefin (PAO) base oil lubrication with each of five additives, especially when oleic acid was 0.2 and 1.5% (by mass), and the wear scar width and friction coefficient of treated samples were 46.9 and 16.4% lower than those of the untreated samples, respectively. Morphological analyses indicated that micromagnetic fields generated during friction tests not only promoted oxidation of the worn surface and debris but also produced thinner tribofilms that included chemical and adsorbed films.     

Effect of Surface Roughening of Substrate Steel on the Improvement of Delamination Strength and Tribological Behavior of Hydrogenated Amorphous Carbon Coating Under Lubricated Conditions

The adhesion strength of diamond-like carbon (DLC) coatings is an obstacle in efforts to improve the reliability of coated products. It is generally believed that the roughening of the substrate surface improves the adhesion between a substrate and coating. The effect of surface roughening of the substrate on the delamination strength of DLC coating and the tribological behavior under lubrication were studied. Five types of roughened substrates were prepared by a wet blast device with differing materials, shapes, and sizes of the shot particles. A hydrogenated DLC film was deposited using plasma-enhanced chemical vapor deposition on the roughened substrates. The tribological properties were investigated under air and lubrication with pure water or n-decane. It was found that the delamination strength of the DLC coating could be improved by roughening the substrate surface, especially by spherical particles. It was also found that slight polishing of either the DLC surface deposited on the rough substrate or the roughened substrate before deposition significantly reduced the wear of the counter surface. The remaining chemical element of alumina particles on the roughened surface affected the delamination strength of the DLC coating.     

The Effect of Applied Load on Tribological Behaviors of Potassium Titanate Whiskers Reinforced PEEK Composites Under Water Lubricated Condition

The tribological behavior of potassium titanate whiskers (PTW) reinforced polyetheretherketone (PEEK) composite has been investigated using the pin-on-disk configuration at different applied loads under water lubricated condition. It was found that the incorporation of the PTW into PEEK would achieve high wear resistance and low friction coefficient at low load. When the applied load increased up to 4 MPa, only the composite filled with 5 wt% PTW showed a significant improvement in the frictional reduction and wear resistance; on the contrary, a rapid increasing of the friction coefficient was observed for the composites of high PTW content. In the meantime, the severe wear loss occurred along with the sharply increasing temperature. This sudden deterioration of the wear resistance should be attributed to the change of the wear mechanism. The main wear mechanism of mild fatigue for the neat PEEK and mild abrasive wear for the 5 wt% PTW filled composite did not alter with the rising of the load. In this case, no transfer film could be detected on the counterpart surface. However, for the high PTW filled composites, the wear mechanism changed from the mild abrasive wear at low applied load to the severe fatigue wear at high load. Large amounts of wear debris were generated by the fatigue-delamination of the composite surface. And then, the debris served as third-body abrasives during the subsequent sliding process and the wear mechanism changed to severe abrasive wear. And unexpectedly, a thick and lumpy transfer film was formed on the counterface.     

Tribological Properties of MCD Films Synthesized Using Different Carbon Sources When Sliding Against Stainless Steel

Tribology Letters - Diamond and diamond-like carbon are used as coating materials for numerous applications, ranging from biomedicine to tribology. Recently, it has been shown that the...     

Effect of Carbon Diffusion on Friction and Wear Behaviors of Diamond-Like Carbon Coating Against Germanium in Boundary Base Oil Lubrication

Tribology Letters - The focus of the research was on investigating the influence of orientation of fibers in graphite fabric-reinforced polyetherimide composite on wear performance in selected wear...     

固化剂对黏结润滑涂层摩擦学性能的影响

以环氧树脂为胶黏剂,聚四氟乙烯、石墨、二硫化钼为固体润滑剂,采用二氨基咪唑三嗪络合物(HT110)和二氨基二苯砜(DDS）2种不同的固化剂制备黏结固体润滑涂层,并在HDM-20端面摩擦磨损试验机上考察2种黏结固体润滑涂层在干摩擦条件下的摩擦磨损性能。结果表明：使用HT110固化剂可以获得更合适的表面组织结构,使黏结固体润滑涂层具有更好的减摩性,更高的耐负荷极压性;固化剂含量对涂层性能的影响显著,当HT110固化剂质量分数为6%~8%时,黏结润滑涂层的摩擦因数最低,具有最好的耐磨和高承载性能。