Friction Mechanism of Polyamide-6 Against Tin Bronze Under the Boundary Lubrication Conditions

Abstract

The friction of polyamide-6 against tin bronze BrO5Tz5S5 is investigated. The experiments on a friction machine MI-1 according to the scheme of «a stationary ring against a rotating roller» arranged by both direct and reverse friction pair are carried out. The reverse pair is tested under both water lubrication and dry condition, whereas the direct pair is tested just under water lubrication. The lubrication is implemented by partially immersing the roller into the tray filled with fresh water. At first every friction pair underwent breakingin with the load equal to that taking place on the surface of real stern-tube bearings during their breaking-in. Then the friction moment is recorded at different loads. When dealing with dry friction, the breaking-in, however, is implemented under water lubrication condition mentioned above, then the roller and the ring are dried thoroughly with paper napkins and fixed again exactly on the previous position. It turned out that friction in polyamide-tin bronze pair under boundary lubrication with water does not depend on the initial roughness of both polyamide and bronze element. And the friction does not depend on the friction scheme (direct or reverse pair) either. Even at comparatively high pressure, characteristic for the real stern-tube bearings breaking-in, the water comes in between the rubbing surfaces. The friction under lubrication condition is caused completely by adhesion, which, in its turn, results from dispersion interaction between adsorbed water films (under water lubrication) or immediately rubbing surfaces (under dry condition). Application of water reduces the friction by 25 % compared to the dry friction.