Abstract
The article presents the results of an aluminum oxide layer doped with monolayer 2H tungsten disulphide (Al2O3/WS2) for applications in oil-free kinematic systems. The results concern the test carried out on the pneumatic actuator operational test stand, which is the actual pneumatic system with electromagnetic control. The cylinders of actuators are made of Ø 40 mm aluminum tube of EN-AW-6063 aluminum alloy which is used in the manufacture of commercial air cylinder actuators. The inner surfaces of the cylinder surfaces were covered with an Al2O3/WS2 oxide layer obtained by anodic oxidation in a three-component electrolyte and in the same electrolyte with the addition of tungsten disulfide 2H-WS2. The layers of Al2O3 and Al2O3/WS2 obtained on the inner surface of the pneumatic actuators were combined with a piston ring made of polytetrafluoroethylene with carbon (T5W) material and piston seals made of polyurethane (PU). The cooperation occurred in the conditions of technically dry friction. After the test was carried out, the scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) analysis of the surface of the cylinder bearing surfaces and piston seals of the pneumatic cylinders was performed. The analysis revealed the formation of a sliding film on the cylinder surface modified with tungsten disulfide, as well as on the surface of wiper seals. Based on the SEM/EDSM tests, it was also found that the modification of the Al2O3 layer with tungsten disulfide contributed to the formation of a sliding film with the presence of WS2 lubricant, which translated into smooth cylinder operation during 180 h of actuator operation. The cylinder with the unmodified layer showed irregular operation after approximately 70 h thereof.
Highlights
Friction is a complex and nonlinear common phenomenon, dependent on many physical parameters and operating conditions in all mechanical systems
After approximately 80 h of the test, a reduction in the speed of the acIn the firstrod hours testing, both actuators powered by air with the2 was same pressure tuator piston withofthe cylinder surface without modification of WS
The research results and their analysis presented in the article confirm the sense of life of pneumatic cylinders with oxide finish, supplied with air not lubricated with oil mist
Summary
Friction is a complex and nonlinear common phenomenon, dependent on many physical parameters and operating conditions in all mechanical systems. It is necessary to minimize the resistance to movement of, inter alia, pneumatic actuators used in many industrial applications to generate force in reciprocating motion. Compared to other reciprocating force devices, such as hydraulic actuators, pneumatic actuators have advantages such as: the possibility of obtaining very high speeds of movement, reliability, low cost, easy installation, easy maintenance and the availability of compressed air in almost all industrial installations. Experimental studies [15,16,17,18] have shown the importance of measuring the friction force of pneumatic and hydraulic actuators, taking into account physical factors such as speed, pressure and other tribological factors. Mazza et al [21] determined how the geometrical and material properties of the piston rod and piston seals relate to the total friction force between the elements of pneumatic cylinders
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