CONICET | Buscador de Institutos y Recursos Humanos

The objective of this work is to study the influence of the skin roughness on the tribological behavior of a lubricated steel-manganese phosphated steel tribosystem, under high pressure sliding contact and low speed, in order to simulate the contact conditions existing on the seal of the threaded joints used in oil and gas casing and tubing strings. Tests were carried out with a modified block-on-ring Timken tribometer and performed by varying rings surface roughness between Ra=1.4 and 2.8 mm. The surface condition was achieved by turning and measured using a roughness profilometer. The load between contact surfaces was applied withing the counterpart block, which was coated with manganese phosphate following the standard procedure used for couplings in TenarisSiderca. As lubricant, a thread compound containing lead, copper, zinc and graphite was used. During each test, load vary linearly between 250 N and 7000 N,, and loading and unloading lasted 14 sec and were performed in opposite directions of rotation to simulate the the make-up and break-out of the connections. Friction force and applied load as a function of time curves were registered. For each case, the friction power intensity model was used to estimate the dissipated frictional energy. Upon completion of the test, worn surfaces were analyzed by SEM, optical microscopy and laser scanning microscope. Wear level was assessed as a function of the volume of material removed in the block using optical microscopy and an specific software according to ASTM G 77 ? 98 standard. The obtained results shows that in the range of roughness studied, the wear damage decrease 34% with the increasing ring roughness. When the ring roughness exceeds the value of Ra = 2.2 mm, a marked increase in the severity of adhesive wear was evident.

enviar mensaje