Rolling Contact Fatigue Evaluation of Advanced Bearing Steels with and Without the Oil Anti-Wear Additive Tricresyl Phosphate

Abstract

The effect of the oil anti-wear additive tricresyl phosphate (TCP) on rolling contact fatigue (RCF) life of advanced bearing steels-AISI VIMVAR M50, CSS 42L, Pyrowear 675, and Cronidur 30 was investigated with silicon nitride balls at 177°C and at a maximum Hertzian stress of 5.5 GPa. TCP at 1% additive concentration was blended into a synthetic polyol ester turbine engine lubricant basestock having a nominal viscosity of 3 cSt at 100°C. Additionally, the basestock was fortified with the antioxidants dioctyl-diphenyl amine (DODPA) and phenyla-napthyl amine (PANA) at 1% concentration each. The presence of TCP has a measurable positive effect on RCF life and wear. Also, all the advanced bearing materials exhibited superior fatigue life compared to conventional bearing steel M50, both with and without TCP. The study indicates that current gas turbine lubricant formulations with TCP have positive effects on fatigue life and wear performance of M50, Pyrowear 675, CSS 42L, and Cronidur 30.

Phosphate Esters, Thiophosphate Esters and Metal Thiophosphates as Lubricant Additives

“…A critical question has been the ability of phosphate esters to form a lubricious film on carbide surfaces. Tricresyl phosphate was shown to be beneficial in all of the advanced bearing alloys [78]. The advanced alloys under current study are all carburized stainless steels.…”

Turbine Engine Lubricant and Additive Degradation Mechanisms

“…Phosphate esters have been shown to interact with the stainless steels in the absence of carburization [38], but in the presence of all three components, metal carbides, phosphate esters and polyol esters the decomposition is much more rapid [39]. When carburized bearings were tested with polyol ester based lubricants formulated with phosphate esters, an increase in fatigue life and wear performance was observed [40].…”

Interaction between Lubricants Containing Phosphate Ester Additives and Stainless Steels

“…Aviation lubricants generally consist of an ester basestock which has added to it amine antioxidants and phosphate esters. A recent study has demonstrated the utility of carburized case hardened bearings with ester based lubricants and phosphate ester additives [12]. Phosphate esters have been shown to form short chain polyphosphate glasses which form a protective film on the bearing surface [13].…”