| Owing to the outstanding combination properties with low density, good corrosion resistance and better specific strength, titanium and titanium alloys are chosen as a new type of oil pipes. However, low hardness and poor tribological properties, especially in sliding situations, including unstable friction coefficients and severe adhesive wear, would lead to appear the phenomenon of corrosion and wear on the surface of titanium and titanium alloys under the extraction of complex environment. Based on the thermal oxidation processing technology (TO) for surface modification of titanium alloys, the present study have shown that the wear resistance and corrosion resistance are improved, due to TiO2oxide layer generated on the surface.In this paper, DMM-400C optical microscopic was used to observe the cross-section morphology of the oxide layer, microstructural examinations of the oxidised samples were conducted by TD-3500X-ray diffraction (XRD), element distribution of oxide layer were analyzed by Glow Discharge Optical Emission Spectrometer (GDS), Micro-hardness values were measured by using HVS-1000Vickers microhardness tester. The CS350electrochemical test system has been used for testing the corrosion resistance of oxide layers in CO2-saturated simulated oilfield solution under the different environmental temperature of30℃and60℃. MFT-R4000reciprocating friction and wear tester was used to carry on the friction and wear experiments under the different load of10N and20N. The tribological properties of the surface modification layer were analyzed by WIVS white light interference in the3D measuring instrument. The following conclusions were obtained:1. After thermally oxidized at600℃～750℃for10h, it was found that the different thickness of the ceramic oxide generated, and oxygen distribution along the modified layer depth into gradient in the surface of Ti6A14V alloy. The surface oxide layer is mainly composed of rutile and oxygen diffusion phase Ti (Ti (O)) phase composition, which has higher hardness than that of the substrate.2. In CO2-saturated simulated oilfield produced fluid, the electrochemical corrosion behavior of untreated and thermal oxidation treated of Ti6A14V alloy at30℃and60℃were discussed. It displays that the corrosion potential of TO treated Ti6A14V alloy are higher than that of untreated one, while, the passivation current of TO treated Ti6A14V alloy are less than that of untreated one. Exceptionally, at675℃and650℃, respectively, has the smallest corrosion current, which is lower two orders of magnitude than the untreated one. It was illustrated that the performance of TO treated Ti6A14V alloy was improved in corrosion. At the same time, TO treated at675℃and650℃has the best corrosion resistance, due to the slowest corrosion rate, respectively.3. Under the different load10N and20N, reciprocating friction and wear testing machine was carried out to study the friction and wear properties of the surface modification layer. The results showed that the friction coefficient of TO treated Ti6A14V alloy was not significantly reduced. According to the value of wear weightlessness and wear rate, TO treated Ti6A14V alloy has better performance in wear resistance,specially,at700℃has the lowest value of wear rate and weight loss under the load of10N and20N. It shows that the wear-resisting behavior of Ti6A14V alloy is best under the condition of700℃/10h process. |
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