Study On Laser Surface Modification Of TA2 Alloy

Titanium and titanium alloys have the advantages of low density,high strength,wide operating temperature（-250℃⁵50℃）,good corrosion resistant and so on.It has been usually applied in aerospace,ship,military,metallurgy,chemical industry,desalination and medical equipment and so on.However,titanium and titanium alloys have some disadvantages such as poor high temperature oxidation resistance,low surface hardness and poor wear resistance.For this reason,people often use surface modification methods to solve this problem.Among them,laser surface modification has been favored because of its advantages such as high efficiency,convenient operation,and good metallurgical bonding with the substrate.In this paper,through laser cladding and laser alloying technology,Ti-Al-Si composite powders with five different proportions are preset on the surface of TA2 substrate.The successfully prepared Ti₅Si₃/Ti₃Al composite coatings have better 1000°C high temperature oxidation resistance,wear resistance and corrosion resistance.XRD,SEM,weight increase method,pin-disk friction,wear method and electrochemical method were used to study the structure and phase composition,high temperature oxidation,wear resistance and corrosion resistance of the coatings.The conclusions are as follows:（1）Ti₅Si₃/Ti₃Al composite coatings with proper ratio are mainly composed of Ti₅Si₃primary phase and Ti₅Si₃/Ti₃Al eutectic structure.（2）The microhardness of the Ti₅Si₃/Ti₃Al composite coatings with proper ratio is higher than that of the substrate.The highest average microhardness of coatings is 734 HV_0.1,which is 3.6 times that of the substrate.（3）Ti₅Si₃/Ti₃Al composite coatings with proper ratio can significantly improve the isothermal air oxidation resistance of TA2 substrate at 1000℃×110 h,and the minimum oxidation weight gain rate is 1/7.45 of TA2 substrate.The oxidation performance of the coatings follows the selective oxidation theory.（4）Ti₅Si₃/Ti₃Al composite coatings significantly improves the wear resistance of the TA2 matrix,and the minimum wear rate is 1/5.7 of the TA2 matrix.The wear mechanism of the coatings is mainly abrasive wear,adhesive wear and oxidative wear,while the wear mechanism of TA2 matrix is mainly adhesive wear and oxidative wear.（5）The highest corrosion potential of Ti₅Si₃/Ti₃Al composite coatings with appropriate ratio in 3.5 wt.%Na Cl solution is-0.63922 V,and the minimum corrosion current density is 2.09×10^-6 A/cm².Corrosion resistance of the coatings is better than that of TA2 matrix.The corrosion mechanism of the coatings is mainly self-corrosion and galvanic corrosion,while the TA2 substrate is mainly self-corrosion.