| ZHANG Mengjia,DI Zechao,LI Yuan,ZHANG Xuetao,HUANG Dongsheng.Effects of Two Types of Phosphorothioate-type Extreme Pressure and Anti-wear Agents on Anti-shudder Performance of Automatic Transmission Fluid[J],53(1):105-114 |
| Effects of Two Types of Phosphorothioate-type Extreme Pressure and Anti-wear Agents on Anti-shudder Performance of Automatic Transmission Fluid |
| Received:January 04, 2023 Revised:September 25, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.01.010 |
| KeyWord:automatic transmission fluid phosphorothioate extreme pressure and anti-wear agent anti-shudder performance friction film |
| Author | Institution |
| ZHANG Mengjia |
Dalian Lubricating Oil Research & Development Institute, Petro China, Liaoling Dalian , China |
| DI Zechao |
Dalian Lubricating Oil Research & Development Institute, Petro China, Liaoling Dalian , China |
| LI Yuan |
Dalian Lubricating Oil Research & Development Institute, Petro China, Liaoling Dalian , China |
| ZHANG Xuetao |
Dalian Lubricating Oil Research & Development Institute, Petro China, Liaoling Dalian , China |
| HUANG Dongsheng |
Dalian Lubricating Oil Research & Development Institute, Petro China, Liaoling Dalian , China |
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| Abstract: |
| The work aims to investigate the effect of two commercialized phosphorothioate-type extreme pressure anti-wear agents, triphenylthiophosphate (AW-1) and acidic sulfur-phosphorus ester (AW-2), on the anti-shudder performance of automatic transmission fluid. Referring to the Japanese JASO M349 standard, a German WAZAU disc-type friction tester that could simulate the working conditions of the automotive clutch plates was used to compare and test the anti-shudder performance of automatic transmission fluid containing the two anti-wear agents. The morphology and elements of the friction surface were further analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive spectrometer (EDS). Although AW-1 and AW-2 were commonly used phosphorothioate-type extreme pressure anti-wear agents in lubricating oils, the form of the friction film formed on the friction pair surface was not the same due to differences in molecular structure. The friction film formed by AW-1 contained sulfur, phosphorus, calcium and other elements, and the content of each element changed to varying degrees as the AW-1 content in the oil increased. The friction film formed by low content AW-2 contained sulfur, phosphorus, calcium and other elements, but the friction film formed by high content AW-2 almost did not contain sulfur, phosphorus, and calcium elements. The contribution of each anti-wear agent to the anti-shudder performance of automatic transmission fluid was different. AW-1 performed better in improving the anti-shudder performance of automatic transmission fluid. The analysis of the post-friction steel discs by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDS) spectroscopy reveals that the mechanism of forming the friction film on the surface of the friction pairs is different for the two types of phosphorothioate-type extreme pressure (EP) anti-wear agents, AW-1 and AW-2. AW-1, a derivative of triphenyl sulfide phosphoric acid ester, generates an S-Fe film on the surface of the friction pair, where the sulfur element in the molecule reacts with the iron element on the metal surface. The phosphorus element in the molecule reacts with the calcium element in the cleaning agent to form a Ca-P film, which exhibits excellent anti-shudder performance. Consequently, AW-1 exhibits superior anti-shudder performance in improving the automatic transmission fluid. On the other hand, AW-2 is an acidic sulfur-phosphorus ester, containing carboxyl groups that react with the iron element on the surface of the steel disc to form a sulfide phosphoric acid ester iron salt. This salt deposits on the metal surface, forming a reactive deposition film. For low concentrations of AW-2, the inhibitory effect on the S-Fe and Ca-P friction films is not significant. However, for high concentrations of AW-2, it inhibits the generation of both S-Fe and Ca-P friction films. Therefore, high concentrations of AW-2 do not contribute to anti-shudder performance. In conclusion, the SEM and EDS results show that the mechanism of forming the friction film on the surface of the friction pairs is different for AW-1 and AW-2. AW-1 generates S-Fe and Ca-P friction films, while AW-2 forms a reactive deposition film. The inhibitory effect of AW-2 on the generation of S-Fe and Ca-P friction films is dependent on its concentration. Thus, understanding the different mechanisms of these EP agents is crucial for selecting the appropriate lubricants to enhance the performance of automatic transmission fluids. |
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