Tribological performance of polyamide 6/wax blend for rolling bearing, bushing and gear applications

Abstract

Today, machine manufacturing is developing rapidly and plastic materials are preferred in some parts of these machines. Rolling bearings, gears, bushings and rollers are some of the machine elements manufactured from plastic in recent years. The working life of the aforementioned machine elements actually depends on the working conditions as well as the material. At the same time, the speed and load carrying capacity of the machine elements or counter materials during operation determine the life of the plastic material. In this experimental study, polyamide 6 polymer, which is among the engineering plastics used in rolling bearings, gears, rollers and bushings, was used. In addition, PA6 polymer blends with 6% wax solid lubricant were produced to increase wear resistance and their tribological performances were investigated. The polyamide 6/wax blend was first produced in granule form in twin screw extruder by compound production method. Then, test specimens were injection molded using the granules. AISI 316L stainless steel was used as a counter-disc in tribology tests. The tests were carried out under dry sliding conditions and at room temperature. Wear tests were carried out on a pin-disc wear tester at two different loads (50 N and 100 N) and four different sliding speeds (0.5, 1.0, 1.5 and 2.0 m/s). The coefficient of friction and specific wear rate of the materials were determined. According to the test results, an increase in the coefficient of friction and specific wear rate of both PA6 polymer and PA6/6% wax blend was observed with increasing sliding speed. At the load and speed ranges studied, the coefficient of friction of pure PA6 polymer varied between 0.25 and 0.36, while the coefficient of friction of PA6/6% wax blend varied between 0.10 and 0.13. The wear rate of PA6 polymer was obtained in the range of 1.2-12x10-4 mm3/Nm, while the wear rate of PA6/6% wax blend was obtained in the range of 1.2-3.0x10-5 mm3/Nm. The addition of 6% wax to PA6 polymer caused a significant decrease in both friction coefficient and wear rate and contact surface temperature.