Influence antifrictional additives on heat generation in rolling contact with slippage

The aim of the study is the investigation of advanced ways to increase the reliability of hypoid gear-tooth systems at high loads. The technological equipment containing such systems include, in particular, drive axles of automotive engines. The risk factor is the rise of temperature because of the metal elastic deformations and sliding friction at significant offset of the instant axes. The present paper studies the influence of triaryl phosphorothionates, as well as zinc and molybdenum (III) dialkyldithiophosphates upon friction force and heat generation at the surface contacts under combined rolling and sliding friction. Rolling and sliding contacts model the friction in hypoid gearing. The dependencies of friction coefficient from the temperature are graphed for lubricating by transmission gear oil with the studied additives introduced into the system. The influence of additives upon the temperature of friction units has been compared together with the efficiency of additives at various temperatures. As follows from the obtained results, both types of the studied additives significantly decrease the friction force at temperatures from 100 °С and more. Addition of phosphorothionates and dialkyl dithiophosphates into the transmission oil composition significantly decreases the friction force and wear intensity at the rolling and sliding contact. Dissimilarity between the studied additives is observed mostly in the temperature ranges, in which the influence of the additives upon tribological properties of transmission oil is evident. For triaryl phosphorothionates this influence is observed at temperatures greater than 100…110 °С. For trialkyl phosphorothionates it exists at temperatures greater than 80 °С. Molybdenum (III) dialkyl thiophosphates with long hydrocarbon radicals lower the friction force practically at all positive temperatures; they exceed phosphorothionates in efficiency. Thus, introduction of additional quantity of the studied additives into transmission oil can substantially decrease both the temperatures reached by the gearing in operation and the wear rate at given temperatures.