Zinc di–alkyl dithio–phosphate (ZnDTP) compounds are widelyused in engine and transmission oils both as anti–oxidants and asanti–wear additives. However, recent work has shown that manyanti–wear additives appear to have a detrimental effect on theresistance of gears and other contacting components to varioustypes of rolling contact fatigue, including micropitting. In thepresent paper we examined the effect of the presence of a secondaryC6 ZnDTP in a low viscosity synthetic base oil on the resistance tomicropitting and wear of carburised steel rollers, using atriple-contact disk tester.
It was found that the additive caused severe micropitting andassociated wear, whereas the pure base oil did not give rise to anymicropitting. It was further found that the additive was notdetrimental unless it was present during the first 100 000 cyclesof the test when it was found to exert a strong effect on thedevelopment of roughness on the counter-rollers. It is concludedthat the additive is detrimental to micropitting resistance becauseit retards wear-in of the contact surfaces, favouring thedevelopment of damaging fatigue cracks. This contrasts with someearlier speculation that suggested a direct chemical effect couldbe responsible.
- Edition:
- 04
- Published:
- 10/01/2004
- Number of Pages:
- 10
- File Size:
- 1 file , 770 KB
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