Applying graphite pellicles formed by electrical discharges in impulse to improve the exploitation performances of metal surfaces [Articol]

Abstract

There is a number of issues such as the effect of wax formation in the pipe plugs during the extraction and transportation of oil (petroleum) through pipelines. For this purpose, different technologies are used to avoid this effect (surface hardening, surface pellicle formation, ultrasound application, etc.). We have developed a technology of graphite pellicle formation by applying electrical discharges in impulse. For this purpose, a rotating tool-electrode made of graphite, included in the circuit of a current pulse generator, is applied, and the work piece serves as a counter-electrode. Continuous or strip-like pellicles are formed by establishing the required parameters of electrical discharge, the interstice size and the frequency of discharge impulse through a relative movement between the tool-electrode and piece. The formation of graphite pellicles on the piece surfaces does not lead to changes in their geometry but gives them new properties. The process of graphite pellicle formation is accompanied by hardening the surfaces made of construction steel by 3 to 8 times at the depth of 3..10 μm. As a result of this type of machining, carbon partially diffuses into the work piece surface with carbide formation. The continuity of processed surface reaches 90...100 % shares and the amount of carbon on the surface exceeds 90 % of carbon. Wear tests of glass mold poansons have demonstrated that they resist over 57 000 cycles without any change of geometry and dimensions. The paraffin casting inside the machined tubes with graphite pellicle formation have shown that it does not adhere to the pipe surface. The graphite pellicle formation on the frontal surfaces of the nuts demonstrates that it omits the effect of their sticking to the mating surfaces. Graphite pellicle formation is possible on flat and rotating surfaces, that is why it may be applied to cover the interior pipe surface in order to avoid the effect of wax formation in the pipes during oil extraction and transportation; in anti-stick pellicle formation in mechanical joints; to increase the wear resistance of form pieces for glass molding.