Effect of Humidity on Wear of M-50 Steel with a Branched Perfluoropolyalkylether Lubricant
Humidity is an uncontrolled variable in many tribology tests. This report shows that changes in relative humidity can affect wear for all perfluoropolyalkylethers regardless of their molecular structure. Using a Cameron–Plint tribometer under controlled environmental conditions, wear of M-50 steel with a Krytox (a branched perfluoropolyalkylether) lubricant was studied under boundary lubrication conditions at 150°C in air with relative humidity ranging from 1 to 95%. Both wear and friction decreased sharply as humidity was increased from 1 to 20%, then were constant as the humidity was increased to 95%. Thus, wear is highly dependent on humidity when relative humidity is less than 20%. The similar effect of humidity on wear previously observed for Fomblin Z, a linear perfluoropolyalkylether containing difluoroacetal groups, and Demnum S, a linear perfluoropolyalkylether which does not contain difluoroacetal groups, indicates that this may be a general property of all commercially available perfluoropolyalkylethers, branched as well as linear ones.
perfluoropolyalkylether, polyether, PFPAE, relative humidity, friction, wear, Krytox
Helmick, L. S. (1999). Effect of Humidity on Wear of M-50 Steel with a Branched Perfluoropolyalkylether Lubricant. Tribology Letters, 6, 123-127.