An experimental determination of kinetic friction for hardened dry steel pairs

Abstract

The effect of pressure-velocity and time on the friction of selected metal combinations at sliding speeds of 22.3 and 54.4 ft min −1 was studied. A pin-disc friction machine was used and friction tests were conducted in which the pin traced a wear path (track) on the outside circumferential edge of the disc. The pressure-velocity value was varied by changing both the force on the pin and the angular velocity of the disc and was based on the Hertz contact pressure and area. The pressure-velocity values were 1.05 × 10 6 and 3.23 × 10 6 Ibf in −2 ft min −1. The specimen material combinations studied were Stellite and boronized and carburized steel pins in dry sliding contact with carburized steel discs. With increased sliding time, surface films were worn away, the real area of contact increased and the friction coefficient increased. The friction values indicated an approach to a steady state value, especially for the low pV tests. The friction coefficients for both pV values were significantly different for the three material combinations tested. The Stellite pin sliding on the carburized disc had the lowest kinetic friction coefficient and the carburized pin sliding on the carburized disc had the highest friction coefficient. The boronized pin sliding on the carburized disc exhibited an initial coefficient comparable with that in the carburized-on-carburized test. Steady state values from the boronized-on-carburized test were, however, significantly lower.