| Among the most important energy sources, petroleum as a vital lifeline of national economy development has been the stratagemical source chased by each nation for a long time. It can find application in every field and works as the running blood for all industrial sections. The Petrochemical industry's status in support industries of national economy makes itself extremely important and indispensable to the national economy. The totally industrial production value of it has accounted for 10% of the gross domestic product (GDP). The petroleum industry in China came into a high-speed developing period in sixties last century, and the exploitation quantity exceeded a hundred million tons in 1978, and the increasing trend has kept year after year since then. The substantial contribution to the petroleum industry owes to the major petroleum enterprises like Daqin, Kalamayi, Shengli and Changqing oil fields.The major oil fields in China have so far entered the evening of petroleum exploitation after a period of over thirty years'contributions to the economic and social development. The challenges faced by these oil fields are the more and more severe exploitation environments including the deeper oil well, higher water containing petroleum, high-corrosion oil well and more application of deviated and horizontal oil wells. The oil extraction equipments including tube and sucker rod works under complex conditions such as high temperature, high multiphase flow, CO2, H2S, ion concentrations, and hence the accidents due to the corrosion cracks of the tube or the partial-wear between the tube and sucker rod happens more frequently than ever, and these two forms of invalidations often simultaneously works together, resulting in a shorter duration exemption from repair, a higher exploitation cost and a lower production of petroleum. The present dissertation has set up the investigation subject of the surface treatments of the sucker rod and tube to improve the wear and corrosion resistance to address the problems mentioned above. According to the working condition and processing of the components in oil well, the investigations consist three parts: first, boronizing of the sucker rod and the sucker rod collar. Second, the investigation on friction and wear properties of several materials for suck rod centralizer application. Third, the microstructure and properties of ceramic-lined tubes using centrifugal self-propagating high-temperature synthesis (SHS) process as well as toughening of the ceramic line. . Boroniziing is a effective thermochemical treatment to increase the surface hardness and wear resistance by creating a bride layer with hardens of 1200-2000HV, excellent wear and corrosion resistance, high temperature strength and antioxidation. The specimens were boronized by means of powder boriding agents containing RE element, in which the addition of Nd2O3 was 0, 1, 3, 5, 7 and 9 wt.%, respectively, the treatment temperature was 1133 K with a holding duration of 5h.The results show that with increasing the content of Nd2O3, the bride layer initially thickens and then decreases, the largest thickness of the bride layer occurs as the content of Nd2O3 reaches 5%. XRD result reveals that the bride layer consists of FeB and Fe2B phases, and the proportion of Fe2B phase increases with more addition of Nd2O3. The non-RE boronized and RE boronized AISI 1045 steels were applied to wear test and worn surfaces were examined, the wear rates of both boronized materials exhibited a dependence on the applied load. The RE boronized material displayed a higher wear rate than that of non-RE boronized material as the applied load was less than 90 N, and afterwards the wear rate of RE boronized material increased gradually and was lower that of non-RE boronized material, especially the higher resistance was prominent as subjected to high load. The wear mechanism was abrasion for two boronized materials, the reason that RE boronized was superior to the non-RE boronized in wear resistance is the bride layer become thicker and the tooth grows compacted towards the substrate, the other reason is that decrease in the FeB phase lessens the internal stress owing to the specific volume and coefficient of thermal expansion of the boride and the substrate.The corrosion resistances of the no-RE boronized and RE boronized materials were investigated by polarization curves in 5vol.% H2SO4 and 5vol.% HCl solutions and immersion tests of oil field water from Songyuan oil well, which contained H2S and had a 7.4 pH value. In order to evaluate the effect of the H2S on the corrosion, the immersion solution was prepared with oil field water with a 0.1mol/L H2S and a 6.8 pH value by pumping H2S gas into it, the specimens were weighed in duration of 10 days'corrosion and the immersion solution was replaced, the immersion time was 240 days. The result shows that the boronizing has little effect on the corrosion potential value but can significantly reduce the corrosion electricity current density, hence improve the corrosion resistance. The calculation shows that the corrosion resistance of RE boronized AISI 8620 is 8.4 and 2.3 times higher than that of AISI8620 steel in H2SO4 and HCl solutions. The analysis of surface morphology and corrosive product of the immersed specimens shows that corrosion pits are formed on the surface of the AISI8620 steel whereas the surface of the boronized material is smooth and no corrosive product is found. The weight loss of the untreated material is 7.5 and 9.8 times as that of the boronized material in two kinds of oil field water, the corrosive product of AISI 8620 is FeS, the FeS is only found on the surface of the boronized material after immersion in the high H2S containing oil field water.In order to investigate the effect of RE element on the boronizing, the AISI 1045 steel and ASTM W1-111/2 steel was boronized using briding agents with 5%Nd2O3 or without RE at boronizing temperatures of 1093K, 1133K, 1173K, and 1213K, respectively for 5 h. The bride layer of all specimens increased with increasing temperature. The bride layers of AISI 1045steel and ASTM W1-111/2 steel boronized with RE boriding agent are thinner than those boronized with non-RE boriding agent at 1053 K. However, the bride layers obtained from RE boriding agent are thicker than those using non-RE boriding agent at high temperatures of 1093K, 1133K,and 1213K, indicating that the accelerating effect can only work at a high temperature level, at low temperature the existence of Nd2O3 prohibits the thermochemical process. The activation energy for AISI 1045 steel without RE addition is 198 kJ/mol, and 137 kJ/mol at high temperature with RE addition. The activation energy for ASTM W1-111/2 steel without RE addition is 251 kJ/mol and 158 kJ/mol at high temperature with RE addition. They reduced by 31% and 21%, respectively, indicating that the effect of RE on boronizing is more significant for AISI 1045 than for W1-111/2 steel. The analysis of constituents in the boriding agent before and after boronizing helps confirm the chemical reaction of Nd2O3 in the process of boronizing: 2BF3 + 3B4C + Nd2O3 + 6O2= 2NdF3 + 2B2O3 + [B] + 3CO↑ΔrGm,Tθof the above reaction, -368.3kJ, by the thermodynamics calculation suggests a great reaction potential and possibility of the reaction at the boronizing temperature. The analyses of SEM and EDS show that the sphere-shaped on the surface of AISI 1045 steel contains Nd, F and K elements, indicating that Nd exert strong attraction to the low atomic order nonmetal elements. The effect of RE elements on the boronizing is summarized on three aspects: (1) The RE oxide in boriding agent takes part in the reaction to produce active B atoms and accelerate the producing process of active B atoms. (2) RE atoms bring large number active B atoms to be adsorbed on the surface of the specimen, which help the interfacial reaction and diffusion of B atoms into the substrate. (3) The absorbed RE atoms diffuse into substrate through interfacial reaction and facilitate the diffusion of B atoms into substrate and the formation of Fe2B phase.The sucker rod centralizers made of glass fiber reinforced polyamide (GF/PA) composite with a greater diameter than the sucker rods, usually fixed in positions such as the ends and the middle of the sucker rod, can protect the sucker rod from being worn by the conventional steel tube to a certain extent. Nevertheless, the GF/PA centralizer was found being worn quickly in a period of less than one month in some deviated wells by the ceramic Al2O3 layer in the ceramic-lined composite steel tubes. Therefore, new centralizer, made of a certain material which could display good wear resistance to the ceramic Al2O3, must be prepared. The present paper compares the friction and wear behavior of QT600-3, quenched QT600-3 and GF/ PA66 composite sliding against ceramic Al2O3 under both dry and oil field water lubricated conditions, and the worn surface and wear data were analyzed.A pin-on-disc apparatus connected to a computer was used to evaluate the friction coefficient of the GF/ PA 66 composite and ductile iron rubbing against ceramic Al2O3 discs under dry and oil field water lubricated conditions at 20N,50N,80N,110N,140N,170 N. The disc rotational speed was kept constant at 4.17×10-2 ms-1 throughout the investigation. The lubricant was the producing water from an oil well in Jilin oilfield of China with a total mineralization of 2.1×104mg/L, which was transported to the wear track on the rotating disc at a flowing speed of 20 drops/min through a plastic tube with a diameter of 3 mm. The GF/ PA 66 composite shows a better wear resistance under dry sliding condition than under oil-field water lubricated condition, especially as the applied load is over 50N, the wear volume increases rapidly and exceeds than of ductile iron. The worn surface of GF/ PA66 composite was destroyed badly as load is over 80 N, for example, the torn matrix and debonding of glass fiber were apparent. The degradation may be ascribed to two main factors such as the hydrolyzation of amide groups and softening. Analyses of XPS and FT-IR spectra confirm that some of the (CH2)n chains are broken in the process of sling against ceramics disc. The thermal deformation temperature of GF/ PA 66 composite is estimated based on the thermal conductivity mold to be 105.9℃.There is a great difference in wear resistance of QT600-3 ductile iron between the dry sliding and water-lubricated conditions, which is ascribed to the plastic deformation and graphite breaking through the top layer of metallic material induced by the frictional heating during dry sliding, and the cooling effect during water-lubricated condition. The quenched QT600-3 exhibits better wear resistance under both dry sliding and water-lubricated conditions, the wear volume keeps a low level and the wear surface is smooth, suggesting that it can be a good choice for sucker rod centralizer.The centrifugal self-propagating high-temperature synthesis (SHS) process has been employed to prepared the ceramic-lined composite steel tube with high operating temperature, corrosion resistance and wear resistance. The present paper focuses on the investigation of the microstructure and mechanical properties including crushing strength and compression-shear strength of the ceramic-lined composite steel tube. The comparative study on the corrosion behavior between N80 tube and the ceramic-lined composite steel tube was performed in a oil field water with high content H2S (0.1mol/L)。The different content of ZrO2 powders were added into thermit like 2, 4, 6, 8 wt.% to improve the toughening effect. The examination of the microstructure and mechanical properties of the ceramic-lined composite steel tube reveals that It consisted of three parts i.e. the ceramic line, iron layer followed by the steel substrate.The ceramic layer is composed ofα-Al2O3 dendrite and FeAl2O4 on the boundary. The crushing load is 17.4 kN, 47.5% higher than the 11.8 kN of N80 tube, and the finite element analysis is used to stimulate the crushing process, and it shows that the upside and underside of the ceramic layer are subjected to tensile stress whereas the left and the right sides are subjected to compressive stress in the process of loading, therefore the ceramic layer cracks firstly in upside and underside positions, then cracks in the left and right positions with the displacement increasing, which agrees well with the experimental result. The bonding strength between the ceramic layer and steel substrate is rather high; the compression-shear strength is 25.6 MPa.The corrosion result in oil field water containing H2S (0.1mol/L) shows that a black film of FeS formed on the surface of the N80 tube, and localized corrosion pits occurs having a thickness over half the tube wall. The ceramic layer surface remains smooth and clear without distinct corrosion sign. This is because of the Al2O3 is a dual material of acid and alkali with high anticorrosion to the chemicals. The microstructure analysis reveals that corrosion strips with 0.5 mm width and 20μm depth have been formed on localized area, the Al2O3 phase is anticorrosion one, but the FeAl2O4 is prone to be etched. Furthermore, the iron layer was etched owing to penetration of corrosive solution through the cracks to the interface between the ceramic layer and iron layer. The corrosion product near the iron layer is the FeS whereas the corrosion product far from the cracks is the iron oxide. Therefore, it is necessary to improve the toughness of the ceramic layer and prevent the cracks from initiating.The yttria-doped ZrO2 power contains 32.1% of m-ZrO2, the other constituent is t-ZrO2. Only t-ZrO2 was detected by XRD in the resultant ZrO2 ceramic layer in the composite tube. The ZrO2 particles of 1μm diameter are distributed on the boundary of theα-Al2O3 dendrites. The ZrO2 has a grain refining effect; the average width of theα-Al2O3 is 7.7μm, decreases by 31.9% as compared with the width of 11.3μm for the conventional ceramic layer. The addition of ZrO2 can effectively improve the fracture toughness of the ceramic layer, for instance, the fracture toughness is 0.88 MPa m1/2 under addition of 2%ZrO2, then significantly increases to 5.93MPa m1/2 with more ZrO2 addition until 6%. Further addition results in a decrease in fracture toughness due to the low fluidity, difficulty in evacuation of gas and the increase in pore ratio at high temperature.On the basis of the investigation, the results in the dissertation could have a positive effect on the improvement and development of the oil production equipment.
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