Parameters influencing the running-in and long-term tribological behaviour of polyamide (PA) against polyacetal (POM) and steel

A. Pogačnik, M. Kalin

Wear 290/291 (2012) 140-148.


This work focuses on a study of the parameters affecting the running-in and long-term behaviour of plastic/plastic and plastic/steel contacts at sliding distances sufficiently long to ensure steady-state sliding conditions, which is very important for an evaluation of the performance in real-scale applications. Unreinforced polyamide (PA6) was paired against stainless steel and against unreinforced polyacetal (POM). The effect of the sample roughness (0.2 and 0.65 μm Ra) and sliding velocity (0.1, 0.5 and 1 m/s) was studied at a constant nominal pressure of 0.7 MPa. In addition, the contact conditions were carefully controlled with measurements of the upper specimen surface temperatures using an infrared camera. The results show that the running-in sliding distances to reach steady-state conditions are much longer for the PA6/POM contacts (up to 45 km) than for the PA6/steel contacts (up to 20 km). For the PA6/steel contact the surface roughness has a significant effect on the coefficient of friction, the sliding distances to steady-state and on the wear mechanisms, while for PA6/POM the effects of these parameters are less influential. For the smooth PA6/steel contacts a transfer film forms on the steel surface, causing adhesion wear, while for the rough steel surface, abrasive wear is dominant. For the PA6/POM contacts, plastic deformations with local melting occur on the PA6 surface at high speeds, mainly due to the poor heat conductivity of the plastic materials, which did not occur at the lower velocity, nor when used against the steel surfaces.

Keywords: polimeri, polimerni materiali, friction


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