Figure - available from: Tribology Letters
This content is subject to copyright. Terms and conditions apply.
Optical microscope images of ball wear scars, their surface height changes, and corresponding wear profiles of the flat after tribotests at 6 N load for 2 h on different steel flats: a 52100, b A2, c D2, and d CF2 steel. Lubricant used: PAO-4
Source publication
We report here the impact of different alloying elements in steels on friction and wear behavior by performing ball-on-flat lubricated reciprocating tribotesting experiments on 52100 ball on steel flats with different compositions (52100, 1045, A2, D2, M2, and a specialty Cu-alloyed steel) heat-treated to give similar hardness and microstructure, w...
Citations
... According to the failure research of mechanical equipment, there are three main failure modes of machine parts: Corrosion, Fracture, and Wear [1][2][3], in which wear accounts for the largest proportion, about 60%-80%, and consumes nearly 1/3-1/2 of energy [4,5]. Therefore, the technology of reducing friction resistance and wear is an effective way to save energy, prolong the service life of mechanical equipment, and improve its working reliability [6,7]. ...
In practical engineering applications, high temperatures and water ingress seriously affect the service life of hydrocarbon lubricants. In this study, the deterioration process of hydrocarbon lubricants under high temperatures and humid environments was investigated, and a new health state prediction model was proposed. Simulation of hydrocarbon lubricant Polyalpha-olefin (PAO) molecules using the ReaxFF force field to analyse the high temperature thermal oxidation process of lubricants. The rheological properties of oil-water emulsions were determined by observing the morphology of oil-water two-phase mixtures with different water contents. A multiparameter fusion viscosity prediction model was proposed using a linear model of the viscosity of aqueous fluids as affected by temperature and water content fitted with the Andrade viscosity-temperature equation to predict lubricant viscosity changes under multiple parameters. On-line validation tests were carried out on a compound planetary transmission system, and the surface topographical parameters of the transmission components were further discussed. The experimental results show that the linear correlation with the improved lubricant viscosity prediction model is 0.966, and the surface wear of transmission components is consistent with the trend of lubricant quality change. These findings provide a fundamental basis for the assessment of lubricant service life in high temperatures and humid environments.
... Raman spectroscopy findings suggest that these carbon layers exhibit a combination of D (at approximately 1351 cm −1 ) and G (at approximately 1580 cm −1 ) bands, characteristic of amorphous carbon structures, consistent with our earlier research [13]. The minor fluctuation in the relative intensity of D and G peaks is ascribed to a greater prevalence of incompletely converted tribopolymers, stemming from the fragments of ethanol molecules, as opposed to decane molecules [52]. ...
... In the case of Co7CuP (Figure 7), the carbon-based nature of the formed tribofilms is also summarized with EDS and Raman maps. Interestingly, the Raman results indicate that the nature of the carbon peaks varies depending on the coating composition and the hydrocarbon source [52]. To further evaluate the variability in the carbon formation, we summarized the changes in the characteristic carbon peaks. ...
Protective coatings are important for enhancing tribological behavior, preventing surface degradation, and reducing friction-induced energy losses during the operation of mechanical systems. Recently, tribocatalytically driven formation of protective carbon films at the contact interface has been demonstrated as a viable approach for repairing and extending the lifetime of protective coatings. Here, we study the effect of catalytic metals, specifically their composition and amount, on the tribocatalysis process. To achieve this, we test the tribological performance of electro-deposited amorphous CoNiP and CoCuP coatings in different hydrocarbon-rich environments. Our results indicate that the tribocatalytic repair of wear-induced damage is optimal when Ni and Cu are included in the Co-P matrix at 5 wt% Ni and 7 wt% Cu, respectively. Characterization of the wear tracks suggests that among the considered samples, the tribofilms formed on the surface of Co7CuP have the highest concentration of graphitic carbon, leading to a more significant reduction in the COF and wear rate. The carbon tribofilm formation was more pronounced in decane and synthetic oil than in ethanol, which is attributed to the difference in the length of the hydrocarbon molecules affecting viscosity and the lubricant film thickness during boundary lubrication sliding.
... The propensity of carbonaceous tribofilm formation on Cu and Pt-group metals was noted above and it is also possible that the carbonaceous film observed on retrieved metal hip implants [29], and in wear tests on such implants [31], is promoted by the presence of catalytic metals in the CoCrMo alloy employed. Recently Khan et al. showed that the extent of carbonaceous film formation and also the level of wear in a reciprocating ball on a flat contact lubricated by PAO varied between steels and suggested that this variation originates from the presence of catalytically active metals and oxides in some alloys [32]. ...
Many previous researchers have reported the formation of carbonaceous tribofilms from organic lubricants on rubbing metallic surfaces. This paper shows that a very important factor in the formation of such tribofilms is the presence or absence of molecular oxygen. When steel surfaces are rubbed in saturated hydrocarbon lubricants in the absence of oxygen, for example in nitrogen or hydrogen gas, carbonaceous films form very readily, resulting in low friction and wear. However, when a significant amount of oxygen is present, as is the case in air, carbonaceous tribofilms are not generally formed, so friction and wear are very high, with values comparable to those seen when no lubricant is present. In situ Raman analysis combined with gas-switching experiments show that the carbonaceous films formed during rubbing when no oxygen is present are rapidly removed during rubbing in air, while tests in which lubricant is removed during a test in N2 indicate that the films are quite weak. This suggests that these carbonaceous films are being continually removed and replenished during rubbing in oxygen-free conditions. It is proposed that these carbonaceous films are formed from hydrocarbyl free radicals that are generated mechanochemically from hydrocarbon molecules during rubbing. In the absence of oxygen, these free radicals then react together to form a carbonaceous film. However, when oxygen is present, the hydrocarbyl free radicals react extremely rapidly with oxygen molecules to produce hydroperoxyl free radicals and so are no longer available to generate a carbonaceous tribofilm.
Graphical abstract
... The propensity of carbonaceous tribo lm formation on Cu and Pt-group metals was noted above and it is also possible that the carbonaceous lm observed on retrieved metal hip implants [29], and in wear tests on such implants [31], is promoted by the presence of catalytic metals in the CoCrMo alloy employed. Recently Khan et al. showed that the extent of carbonaceous lm formation and also the level of wear in a reciprocating ball on at contact lubricated by PAO varied between steels and suggested that this variation originates from the presence of catalytically-active metals and oxides in some alloys [32]. ...
Many previous researchers have reported the formation of carbonaceous tribofilms from organic lubricants on rubbing metallic surfaces. This paper shows that a very important factor in the formation of such tribofilms is the presence or absence of molecular oxygen. When steel surfaces are rubbed in saturated hydrocarbon lubricants in the absence of oxygen, for example in nitrogen or hydrogen gas, carbonaceous films form very readily, resulting in low friction and wear. However, when a significant amount of oxygen is present, as is the case in air, carbonaceous tribofilms are not generally formed, so friction and wear are very high, with values comparable to those seen when no lubricant is present.
In-situ Raman analysis combined with gas switching experiments shows that the carbonaceous films formed during rubbing when no oxygen is present are rapidly removed during rubbing in air, while tests in which lubricant is removed during a test in N2 indicate that the films are quite weak. This suggests that these carbonaceous films are being continually removed and replenished during rubbing in oxygen-free conditions.
It is proposed that these carbonaceous films are formed from hydrocarbyl free radicals that are generated mechanochemically from hydrocarbon molecules during rubbing. In the absence of oxygen, these free radicals then react together to form a carbonaceous film. However, when oxygen is present, the hydrocarbyl free radicals react extremely rapidly with oxygen molecules to produce hydroperoxyl free radicals and so are no longer available to generate a carbonaceous tribofilm.
... The latter are speci cally called tribochemical reactions [2]. Various reactions can occur upon shear of molecules at tribological interfaces; these include degradation or fragmentation (dissociation) whose products will desorb or diffuse into the surrounding medium and/or formation of tribo lms that remain on the surface and provide bene cial lubrication effects [3][4][5][6][7][8][9][10]. Tribo lms, present inside the sliding track or piled up around the contact region, are often analyzed with Raman spectroscopy [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. This technique is used because it provides vibrational spectroscopic information of 'small amounts' of samples. ...
... Many Raman spectra of tribo lms reported in the literature show two characteristic vibrational bands of diamond-like carbon (DLC) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] at ~ 1360 cm − 1 and ~ 1570 cm − 1 , which are called D-and G-bands, respectively [31,32]. Note that this feature is typical of almost all amorphous carbon (a-C) materials, including cokes produced by thermal degradation of organics [31][32][33][34][35][36][37]. ...
... Both substrate and ball have a Vickers hardness about 800 HV. The at D2 substrate was used for this experiment instead of 52100 because a larger production of tribo lm was observed with the D2 steel than 52100 when lubricated with dodecane [29]. The test was conducted for 5 hours at normal load of 5 N and sliding speed of 1 m/s, with the contact being fully ooded in dodecane. ...
Many previous studies of tribofilms have interpreted D- and G-bands in Raman spectra as evidence that diamond-like carbon (DLC) was formed during sliding. DLC and other amorphous-carbon films are produced by high-energy processes or high-temperature pyrolysis. Since neither of these conditions commonly occurs in a sliding interface, it seems unlikely that such materials could be produced during simple frictional sliding. To understand this apparent contradiction, we systematically analyzed tribofilms produced from vapor and liquid lubrication experiments using Raman spectroscopy with varied laser power and wavelength. The results provide evidence that DLC-like features in Raman spectra of tribofilms formed from organic molecules originate, not by tribochemical synthesis in situ during the tribo-testing as suggested previously, but rather from post-synthesis photochemical degradation of carbonaceous organic matter during the Raman analysis.
