Preparation Of SiCp / Al-Cu-Mg Composites For Drill Pipe And Its Microstructure And Mechanical Properties

The aluminum alloy drill pipe had the advantages of low density,high specific strength, low elastic modulus,good low temperature performance and good corrosion resistance,so it was applied to oil and gas drilling in the Russia,Japan,America and other countries.But,the the characteristics of aluminum alloy drill pipe included low hardness, poor wear resistance and high temperature mechanical performance, which limited its application in oil and gas drilling. SiC particle reinforced aluminum matrix composite not only had low density,high specific strength and stiffness, but also had good abrasion resistance, low coefficient of thermal expansion. The purpose of this paper was exploration and development of SiC particle reinforced aluminum alloy composites drill pipe which was used for substuting steel drill pipe and aluminum alloy drill pipe,and the preparation process and mechanical behavior of the SiC particle reinforced Al-Cu-Mg alloy matrix composites (SiCp/Al-Cu-Mg) was studied systematically.In this experiment,the different mass fraction of SiC particles (2.5%,4.5%,6.5%) reinforced Al-Cu-Mg alloy composites were casted successfully by adding SiC particles which after1200℃high temperature oxidation pretreatment (the average particle size of15μm) and AZ31magnesium alloy which was lwt.%of the total raw material,by using ZG-25type vacuum intermediate frequency induction furnace.The xSiCp/Al-Cu-Mg composites were homogenized by using the resistance furnace (24℃heat for24hours and water quenching). The xSiCp/Al-Cu-Mg composites were hot-extruded into plates by using the LXJ-300T type extruder hot extrusion.The microstructure of xSiCp/Al-Cu-Mg composites were analysed by using optical microscope, XRD, SEM. the hardness.The tensile properties and compressive properties at different temperatures of the extruded Al-Cu-Mg alloy and xSiCp/Al-Cu-Mg composite were tested by the Brinell hardness tester, universal testing machine and Gleeble1500thermal simulation machine, and the effect of the content of SiC particles on the mechanical properties of the composites were investigated. In addition, The sliding wear and impact-sliding abrasive wear of the Al-Cu-Mg matrix alloy and xSiCp/Al-Cu-Mg composites were tested under simulating drilling condition by using M-2000type wear test machine and MLD-10abrasive wear testing machine. The morphology and composition of the wear surface of xSiCp/Al-Cu-Mg composites were analysed by using SEM and EDS,and the wear mechanism of xSiCp/Al-Cu-Mg composites were investigated.The result showed that:the SiC particles without pretreatment and molten Al were not wetting and float in the molten surface, but the SiC particles with1200℃high temperature oxidation and the addition of1wt.%AZ31magnesium alloy can effectively improve the wettability and the interfacial reaction between SiC particles and molten Al when vacuum casting xSiCp/Al-Cu-Mg composites,and the main product is MgAl2O4in the interface and good combination with substrate. As cast xSiCp/Al-Cu-Mg composite microstructure is mainly composed of a(Al) phase,S(Al2CuMg) phase,θ(CuAl2) phase, SiC reinforce phase, MgAl2O4phase, and the grain boundaries are continuous and grain shape was irregular,SiC particles were mainly distributed in the grain boundary and some SiC particles have agglomeration. After homogenization, the grain boundary is continuous and grain shape was equiaxed,S (Al2CuMg) phase solid solution into the matrix.After hot extrusion,the microstructure of xSiCp/Al-Cu-Mg composites is mainly composed of a(Al) phase,SiC reinforced phase,MgAl2O4phase,and S(Al2CuMg) phase and θ(CuAl2) phase were completely soluted into the matrix,and the grains were strip form which were elongated along the extrusion direction, and the SiC particles dispersed in perpendicular to the extrusion direction and were a strip distribution in parallel to the extrusion direction.Vacuum casting, homogenization treatment and preparation process of hot extrusion is improved distribution of the SiC particles and microstructure of xSiCp/Al-Cu-Mg composite in a certain extent.In addition, under the condition of room temperature, compared with the Al-Cu-Mg alloy, when the content of SiC particles of the extruded SiCp/Al-Cu-Mg composites increased to6.5%,hardness,tensile yield strength,tensile strength, compressive yield strength and compressive strength of the composite increased respectively23.5%,4.3%,5.1%,15.2%and8.5%,and can satisfy the requirements of the national standard of aluminum alloy pipe.Furthermore,with the increase of compression temperature, the composite compressive yield strength and the ultimate compressive strength are decreased. And when the temperature reached200degrees, the compression yield strength and ultimate compressive strength of6.5%SiCp/Al-Cu-Mg composite decreased by17.9%(289MPa) and23.9%(417MPa), it can not reach the standard requirements of aluminum alloy drill pipe, so its highest use temperature can not be more than200degrees as the drill pipe materials. The addition of SiC particles can effectively improve the high temperature softening of Al-Cu-Mg alloy under stress in250degrees and improve the material’s stability of high strength. With the concentration of SiC particles in Al-Cu-Mg matrix alloy reached6.5%, the sliding wear rate of materials decreased by80%. When the SiC particle content reaches4.5%, the sliding wear mechanism of xSiCp/Al-Cu-Mg composite turned into abrasive wear from adhesive wear.The impact-sliding abrasive wear rate of6.5%SiCp/Al-Cu-Mg composite decreased by18.6%compared with Al-Cu-Mg alloy. The impact-sliding abrasive wear mechanism of Al-Cu-Mg matrix alloy and xSiCp/Al-Cu-Mg composite were both the combination of abrasive wear and adhesive wear. The impact-sliding abrasive wear rate of Al-Cu-Mg matrix alloy and xSiCp/Al-Cu-Mg composite increased first and then turned constant.with the increase of wear time. In addition, the impact-sliding abrasive wear rate of6.5%SiCp/Al-Cu-Mg composite reached about30times than its sliding wear rate. The impact-sliding abrasive wear led more damages, which was the main way of drill pipe wear damages.