Investigation Of The Friction And Wear Properties Of Nano-Si₃N₄ Filled PTFE Composites

PTFE has many excellent properties, such as, excellent self-lubrication, low friction, chemistry stabilization and thermal stabilization, but it has low mechanics characters and wear resistance. Many different kinds of fillers can improve its mechanics characters and wear resistance. In this paper, the wear and friction properties of PTFE filled with nano-Si₃N₄ and other inorganic-material have been studied. PTFE composite have obtained by mechanical mixture and compression molding. With MM-200 wear and friction tester, the wear mass loss and friction coefficient of PTFE composite in dry sliding have been evaluated. Scanning Electronic Microscopy (SEM) is used to describe the worn surface. The wear improve mechanism of nano-Si₃N₄ and graphite, nano-Al₂O₃, MoS₂ was studied. In this paper, the fractal character of worn surface of PTFE composite was also studied. With the strong digital image tool module of MATLAB and fractal geometry method, the fractal dimension of PTFE composite worn surface was calculated, fractal dimension can describe the worn surface of PTFE composite.The results indicate that nano-Si₃N₄ can improve wear resistance of PTFE, and wear mass loss of PTFE decrease with the increase of nano-Si₃N₄, meanwhile the friction coefficient increase a little. PTFE filled with nano-Si₃N₄ and graphite or nano-Al₂O₃ or M0S2 improve wear resistance much more than only filled nano-Si₃N₄. In the condition of this experiment, PTFE filled 5% nano-Si₃N₄, 5% graphite and 5% nano-Al₂O₃ have the best wear resistance. The worn surface of PTFE composite has obvious fractal character. The bigger fractal dimension is, the more serious worn surface is. Fractal dimension can describe the wear mass loss of PTFE composite.