The Research On Tribological Properties Of The New Sealing Materials For Stirling Engine

Stirling engine is a kind of heat engine which relies on the external heat source to heat the gas working medium sealed in the machine, so that it can continue to thermal expansion and contraction, so as to push the piston work. The working medium seal is one of the key technologies of Stirling engine and one of the most difficult problems to solve. The leakage of gas working medium will lead directly to the reduction of engine power and efficiency,which will even cause serious safety problems.Therefore the abrasion resistance, self-lubricity and thermal stability of the sealing material are closely related to the power, efficiency and reliability of the Stirling machine. It is important to study the friction and wear properties of the sealing material to enhance the performance of the engine.In this paper, the properties between different materials were compared, and Nanometer SiC (Nano-SiC) and polyimide (PI) were selected as filler.Polytetrafluoroethylene (PTFE) composites were prepared by mixing them with different volume ratio and PTFE in the high speed mechanical mixer, and then by cold press molding and sintering with temperature control program. The tribological behavior of composites and the worn surface temperature was tested by a MRH-3 block-on-ring friction and wear tester under different conditions. The worn surface and transfer film were inspected and analyzed with scanning electronic microscopy(SEM). The results demonstrated that the effect of polyimide on the modification of polytetrafluoroethylene was significant. When the polyimide content was 5%,the friction coefficient of the composite was reduced to 0.182, and the abrasion resistance was greatly improved. The addition of nanometer particles can further enhance the mechanical properties and friction and wear properties of the composites. When the nanometer particles content was 5%, the friction and wear properties of composite materials to enhance the most significant. The change of the worn surface temperature,the tribological behavior, the worn surface morphology and the transfer film of composites related to the content of nano-SiC, load and sliding velocity. With the increase content of nano-particles, the friction temperature rise more quickly into the steady stage, which is helpful to reduce the wear rate of the composite. When the load increased from 100 N to 400 N and the velocity increased from 1 m/s to 4 m/s, the tribological behavior of composites have fallen sharply, the surface morphology and the transfer film changed significantly. The wear rate of the composites under heavy and high velocity conditions was high. The ambient temperature at 25 to 135 ℃within the scope of the impact on the tribological behavior are not obvious.