Research On The Effect Of Rare Earth On Microstructure And Properties Of Casing Steel Packing Cementation Aluminizing

With the deepening of oil and gas exploration and development,the increasingly stringent downhole environment has increasingly higher requirements on the performance of petroleum casing.Aluminizing the surface of the material can effectively improve its corrosion resistance and high temperature oxidation resistance.Due to its special structure,the rare earth element can promote the aluminizing process,reduce the temperature required for aluminizing,and improve the use of the material while maintaining the mechanical properties life.Under this background,this article uses the Adsorption Locator module of Materials Studio for modeling,analyzes the role of different rare earth elements in the process of aluminizing,and under the guidance of the simulation results,the method of embedding aluminized aluminum with rare earth promoted powder,a uniform and dense aluminized layer was successfully prepared on the P110 substrateat 650?.The effect of rare earth concentration and type on the morphology of the infiltrated layer is analyzed.The combination of electrochemical testing technology and weightlessness method reveals the corrosion mechanism and main failure modes of the infiltrated layer,and evaluates the corrosion resistance of each material.Constant temperature kinetic curves were used to analyze the high-temperature oxidation behavior of different materials,revealing the high-temperature oxidation mechanism of aluminized samples,and evaluating the high-temperature oxidation resistance of each material.The main research conclusions obtained in this paper are as follows:?1?Rare earth elements can improve the adsorption energy of Al atoms during the aluminizing process,thereby catalyzing the process of aluminizing.The compound addition of La and Ce two rare earth elements can make Al atoms obtain the maximum adsorption energy;when adding a single rare earth,the infiltration layer The thickness showed a trend of increasing first and then decreasing.The thickness of the aluminized layer added with 1%rare earth oxide was the largest;the quality of the infiltrated layer increased with the increase of the concentration of rare earth added.Control the total addition amount of rare earth oxide to2%,and adjust the addition ratio of La₂O₃and CeO₂.When the addition amount of rare earth oxide is 0.4%La₂O₃/1.6%CeO₂and 0.8%La₂O₃/1.2%CeO₂,the structure of the aluminized layer obtained is the most uniform Dense.?2?After adding rare earth oxide to promote infiltration,the polarization resistance of the sample is significantly increased,and the passivation zone appears in the polarization curve.The corrosion failure form is mainly pitting.When a single rare earth oxide with different concentrations is added to the aluminizing agent,the corrosion resistance of the material increases first and then decreases with the increase in the concentration of the rare earth oxide.The maximum polarization resistance occurs when 2%rare earth oxide is added to promote the penetration.Controlling the total amount of rare earth oxides added is 2%,and the polarization resistance of the aluminized sample obtained by adjusting the addition ratio of La₂O₃and CeO₂is larger,the passivation interval is wider,and the dimensional passive current density is smaller.In 3.5%Na Cl solution,the average corrosion rate of the matrix material P110 is 0.1229mm·a^-1,the average corrosion rate of the rare earth-free aluminum penetration-promoting samples is 0.1062mm·a^-1,and the average rare earth addition-promoting aluminum penetration samples are average The corrosion rate was significantly reduced in different degrees.The average corrosion rate of the sample with0.4%La₂O₃/1.6%CeO₂promoted penetration was the smallest,0.0032mm·a^-1,and the average corrosion rate was only 2.604%of the matrix material.?3?Compared with the matrix and the non-rare earth aluminized material,the rare earth element added aluminizing sample has significantly improved high temperature oxidation resistance:oxidation at 300?for 120h.The following;oxidation at 600?for 120h,the oxidative weight gain of the rare earth penetration-promoting sample is only less than 1/45 of the matrix material.There is no obvious difference in the high-temperature oxidation resistance of the rare earth penetration-promoting samples,and the concentration and type of rare earth oxide added have little effect on the high-temperature oxidation resistance of the material.