Interaction of fomblin^® lubricant with surface nitrided and/or coated bearing (M50) steel

Abstract

High-temperature perfl uoropolalkylether lubricants including Fomblin ® are susceptible to degradation and cause corrosion in the presence of ferrous metals such as M50 bearing steel. This paper describes the effect of surface treatment (nitriding), coating chemistry and architecture in preventing corrosion/oxidation of M50 steel and thermo-oxidative degradation of Fomblin ® fl uid. Specifi cally, Cr-CrN multilayered coating architecture was used with and without a nitrided steel surface. The oxidation/corrosion tests were conducted by immersing the nitrided and/or coated M50 coupons in Fomblin ® fl uid in an oxidative environment at 270°C for 24 h and compared with untreated/uncoated coupons. It is shown that a considerable lessening of the corrosion of the steel and degradation of the Fomblin ® fl uid can be achieved by nitriding alone. Nitriding in combination with the multilayered Cr-CrN coating exhibited the best protection. The results are discussed in relation to the literature data.

Dry tribological properties of M50 bearing steel under different temperatures

“…In fact, the process of forming and breaking tribolayer is a dynamic balance state on the wear surface during the sliding friction tests [25][26][27]. The wear surface is broken under the combined actions of shearing stress and oxidation, and the particles fall off from the matrix, leading to the formation of the spalling pits [28,29] Some of the particles escape out of the wear surface and form wear debris, and others are filled in the spalling pits and compacted again to restore the tribolayer.…”