Rolling fatigue tests of three polyglycol lubricants

In this work, the rolling fatigue lives of three polyglycols (PAG-9, PAG-12 and BREOX-B-135X) are determined using IP-300 standard. A four-ball test machine was used and 10% life (L₁₀) and 50% life (L₅₀) were obtained. In addition, the stress-time curves for L₁₀ and L₅₀ were also determined. This work showed that: firstly, all polyglycols were tested under boundary lubrication regime (λ < 1) where in rolling contacts the surface mode of failures prevails; secondly, in oils of the same family, the pressure-viscosity coefficient is relatively constant, therefore an increase in viscosity improve the minimum film thickness with the consequent increase of the λ ratio; and finally, differences in λ ratio for the three polyglycols resulted in different asperity interactions and rolling contact fatigue lives.