Friction and Wear of Unlubricated Steel Surfaces at Speeds up to 655 FT/S

Abstract

The friction force between 1/8, 3/32 and 1/16 in diameter, and the wear of 3/32 in diameter, specimens of En 1A steel sliding on a disc of S62 steel are measured at speeds between 93 and 655 ft/s, the normal load on the specimen varying between 0.2 and 4.5 lbf. The coefficient of friction is shown to be dependent on sliding speed, normal load and specimen diameter, and to be a function of N1/2 U, where N is the normal load and U is the sliding speed. It is suggested that the coefficient of friction is dependent on the specimen contact surface condition which is dependent on the specimen surface temperature. There is evidence to suggest a gradual change in the mechanism of sliding with increasing magnitude of N1/2 U from, (i) metallic abrasion and tearing of an oxide layer, (ii) to skidding on and shallow ploughing of an oxide layer, (iii) to gliding over and shearing of a soft surface layer. It appears that the coefficient of friction is independent of, whereas specimen wear is dependent on, the disc surface condition. At low loads the material transferred from the specimen tends to form a continuous oxide layer on the disc., while at high loads there is the formation and tearing of a thick oxide layer, presenting a more abrasive surface to the specimen with a relative increase in wear. Generally specimen wear per sliding distance increases with N and decreases with U.