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

High-temperature perfluoropolalkylether 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® fluid. Specifically, 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® fluid 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® fluid 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. Copyright © 2009 John Wiley and Sons, Ltd.