In-situ observations of the effect of the ZDDP tribofilm growth on micropitting

Ueda, Mao; Spikes, H. A.; Kadiric, Amir

doi:10.1016/j.triboint.2019.06.007

Cited by 47 publications

(27 citation statements)

References 16 publications

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“…Zhou et al [10] studied the influence of contact severity on micropitting, and the results of simulation and experiment illustrated that the final surface damage is influenced by the combination of micropitting and mild wear. Lately, a series of in-situ measurements of micropitting performed by Ueda et al [11] strongly supported this competition mechanism. It is presented that higher Zinc Dialkyldithiophosphate (ZDDP) concentrations cause more micropitting and less surface wear.…”

Section: Introductionmentioning

confidence: 91%

“…where is total load, is sliding distance in a certain time, is the material hardness and denotes wear coefficient. Considering the sliding distance and the contact area in a certain time, the removed layer height ℎ is, ℎ = ̅ , (11) where ̅ denotes the mean pressure defined as the ratio of normal load to contact area, is the relative sliding speed. One can replace the time by the contact length , the grid pressure ( , ) and the speed of the current surface , so the equation becomes…”

Section: Wear Modelmentioning

confidence: 99%

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A Micropitting Study Considering Rough Sliding and Mild Wear

2019

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Micropitting is a typical surface contact fatigue in rolling–sliding contact. The kinematic sliding is of great significance in the initiation and progression of micropitting. A numerical surface fatigue model considering rolling–sliding contact and surface evolution is developed based on mixed-EHL (elastohydrodynamic lubrication) theory, rainflow cycle counting method and Archard’s law. Surface evolution is evaluated using Archard’s wear law based on measured teeth surface topography. Surface damage is determined via the Palmgren–Miner line rule and Goodman diagrams. The effect of rolling speed and surface roughness are discussed in detail. Results show that stress micro-cycles are introduced by rough sliding in the rolling–sliding contact. The mild wear reduces the height of asperities, the maximum pressure and alleviates subsurface stress concentration. For rolling–sliding contact, the faster moving surface dominates the composite height of asperities, then decides the fluctuations of pressure, as well as stress ranges. The combination of surface topography should be considered in the surface design.

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Section: Introductionmentioning

confidence: 91%

Section: Wear Modelmentioning

confidence: 99%

A Micropitting Study Considering Rough Sliding and Mild Wear

2019

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“…These asperity stresses occur in high pressure contacts when surfaces are separated only by very thin lubricant films and are thus becoming more prevalent as lubricant viscosities are reduced in the quest for improved fuel economy. Although micropitting is primarily a mechanically driven process it has been found to be accelerated by ZDDPs [9][10][11]. This is because ZDDPs inhibit running-in, by forming tribofilms so rapidly that asperities present on the surfaces from manufacture do not have time to be smoothed or rounded.…”

Section: Zddpsmentioning

confidence: 99%

Tribofilm Formation, Friction and Wear-Reducing Properties of Some Phosphorus-Containing Antiwear Additives

Luiz

Spikes

2020

Tribol Lett

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The film-forming, friction and wear properties of a range of model and commercial ashless P and P/S antiwear additives have been studied. A method has been developed for removing the tribofilms formed by such additives in order to effectively quantify mild wear. In general the P/S additives studied formed thinner tribofilms but gave lower wear than the S-free P ones. In extended wear tests, three P/S additives gave wear as low, or lower, than a primary zinc dialkyldithiophosphate (ZDDP). For almost all lubricants tested the wear rate measured in short tests was considerably higher than that in long tests due to the greater contribution of running-in wear in the former. This highlights the importance of basing antiwear additive choice on reasonably long tests, where running-in becomes only a small component of the wear measured. It has been found that for both P and P/S ashless additives the addition of oil-soluble metal compounds based on Ti and Ca boosts tribofilm formation and can lead to very thick films, comparable to those formed by ZDDP. However, this thick film formation tends to be accompanied by an increase in mixed friction and also does not appear to reduce wear but may even increase it.

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“…This would imply that in many practical situations with moderately rough virgin surfaces there may be no detrimental effect on the shape of the Stribeck curve and no additional asperity stresses caused directly by the roughness of the ZDDP film itself. This is separate from the well-established mechanism in which ZDDP tribolfilms increase severity of asperity stresses through suppression of running-in and in turn, increase the risk of micropitting [41][42][43].…”

Section: Tribofilm Roughnessmentioning

confidence: 76%

The Influence of Steel Composition on the Formation and Effectiveness of Anti-wear Films in Tribological Contacts

Pagkalis

Spikes

Rydel³

et al. 2021

Tribol Lett

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The effectiveness of antiwear additives in laboratory tests is commonly evaluated using specimens made of AISI 52100 through-hardened bearing steel. However, many lubricated machine components are made of steels with significantly different material compositions, which raises an important practical question of whether the performance of antiwear additives with these other steel types is different from that established with AISI 52100. To help answer this question, this paper investigates the influence of steel composition on the formation and effectiveness of antiwear films. Four steels that are commonly used in tribological applications, namely AISI 52100 through-hardened bearing steel, 16MnCr5 case-carburised gear steel, M2 high speed steel and 440C stainless steel are tested in rolling-sliding, ball-on-disc contacts lubricated with three custom-made oils, one containing ZDDP and two containing different types of ashless antiwear additives. The relative effectiveness of their boundary films was assessed by measuring their thickness and associated wear and friction over 12 h of rubbing at two specimen roughness levels. For ZDDP it was found that the formation of antiwear film was not significantly influenced by steel composition or specimen surface roughness. A similar tribofilm thickness, final tribofilm roughness and friction was observed with all four steels. No measurable wear was observed. By contrast, for the ashless antiwear additives the thickness and effectiveness of their tribofilms was strongly influenced by steel composition, particularly at higher roughness levels. The exact trends in film thickness vs steel relationship depended on the specific chemistry of the ashless additive (ester-based or acid-based) but in general, relative to AISI 52100 steel, M2 steel promoted ashless tribofilm formation whilst 440C retarded ashless tribofilm formation. This behaviour is attributed to the presence of different alloying elements and the ability of the additives to extract metal cations from the rubbing surfaces to support the growth of a tribofilm. In all cases ZDDP films were thicker and rougher, and produced higher friction than those formed by the ashless additives. However, unlike ZDDP, ashless blends generally produced significant wear, particularly with 16MnCr5 and M2 steels. The results indicate that to ensure reliable performance of a given machine component, the chemistry of an ashless antiwear additive should be matched with the types of steel present in the lubricated machine.

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In-situ observations of the effect of the ZDDP tribofilm growth on micropitting

Cited by 47 publications

References 16 publications

A Micropitting Study Considering Rough Sliding and Mild Wear

A Micropitting Study Considering Rough Sliding and Mild Wear

Tribofilm Formation, Friction and Wear-Reducing Properties of Some Phosphorus-Containing Antiwear Additives

The Influence of Steel Composition on the Formation and Effectiveness of Anti-wear Films in Tribological Contacts

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