激光熔化沉积TiB_(2)增强TiAl基合金涂层的组织及力学性能  

Microstructure and Mechanical Properties of TiB_(2) Reinforced TiAl-Based Alloy Coatings Prepared by Laser Melting Deposition

作　　者：王虎 赵琳[1] 彭云[1] 蔡啸涛 田志凌[1] WANG Hu;ZHAO Lin;PENG Yun;CAI Xiaotao;TIAN Zhiling(Welding Research Institute,Central Iron&Steel Research Institute,Beijing 100081,China;College of Materials Engineering,North China Institute of Aerospace Engineering,Langfang 065000,China)

机构地区：[1]钢铁研究总院焊接研究所,北京100081 [2]北华航天工业学院材料工程学院,廊坊065000

出　　处：《金属学报》2023年第2期226-236,共11页Acta Metallurgica Sinica

基　　金：国家重点研发计划项目No.2020YFE0200900。

摘　　要：采用激光熔化沉积在TC4合金表面制备出不同TiB_(2)含量(0、10%、20%、30%,质量分数)的TiAl基合金涂层,利用XRD、OM、SEM、显微硬度计、压痕法(断裂韧性)、磨损试验机以及激光共聚焦显微镜等,系统研究了TiB_(2)含量对涂层微观组织与力学性能的影响。结果表明,涂层组织由底部沿厚度方向依次为平面晶、柱状晶和等轴晶,随着TiB_(2)含量增加,柱状晶高度逐渐降低。TiB_(2)/TiAl复合涂层由TiAl合金基体相(γ+α2)以及TiB_(2)增强相组成,直接添加的TiB_(2)颗粒大多没有熔化,但直接添加的TiB_(2)颗粒外层与TiAl合金熔体发生溶解反应后原位析出初生TiB_(2)和次生TiB_(2),初生TiB_(2)呈块状,次生TiB_(2)呈短棒状和条带状。随着TiB_(2)含量由0增加至10%,涂层基体组织明显细化,但继续增加TiB_(2)含量(20%、30%)并未产生进一步的细化作用。随着TiB_(2)含量由0增加至30%,涂层的表面硬度由530.5 HV增加至738.4 HV,断裂韧性由7.75 MPa·m^(1/2)降低至3.17 MPa·m^(1/2),磨损率由3.98 mg/mm^(2)减少至0.42 mg/mm^(2),并且磨损面的磨损程度及其粗糙度也随之降低。未添加TiB_(2)时,涂层的磨损机制以显微切削为主,多次塑性变形为辅;TiB_(2)含量为10%时,涂层的磨损机制以显微切削为主,微观断裂为辅;随着TiB_(2)含量增加,磨损机制逐渐转向微观断裂;TiB_(2)含量为30%时,涂层的磨损机制以微观断裂为主,显微切削为辅。TiAl-based alloy coating produced by laser melting deposition exhibits excellent properties of high temperature and corrosion resistance and has a wide application potential across many fields.However,the wear resistance of the coating is poor,which limits its long-term usage in harsh and complex working environments.In this study,TiB_(2) reinforced TiAl-based alloy composite coatings are prepared by laser melting deposition to improve their wear resistance,and a theoretical reference for further exploring the applications of TiAl-based alloy composites in surface engineering is presented.TiAl-based alloy coatings with different TiB_(2) contents(0,10%,20%,30%,mass fraction)were prepared on the surface of TC4 alloy using the laser melting deposition process.The effects of TiB_(2) content on the microstructure and mechanical properties of the coatings were systematically studied using XRD,OM,SEM,microhardness tester,indentation method,wear tester,and laser confocal microscope.Planar,columnar,and equiaxed crystal distributions were observed along the thickness direction from the bottom.With an increase in TiB_(2) content,the height of columnar crystal gradually decreased.TiB_(2)/TiAl composite coatings are composed of a TiAl alloy matrix phase(γ+α2)and a TiB_(2) enhanced phase.Most of the directly added TiB_(2) particles do not melt,but the outer layer of the directly added TiB_(2) particles dissolves within the molten TiAl alloy,following which primary and secondary TiB_(2) are precipitated in situ.The primary TiB_(2) has a particle form and the secondary TiB_(2) has a needle or flake form.With the increase of TiB_(2) content from 0 to 10%,the matrix of the coating is noticeably refined,but an increase in TiB_(2) content(20%and 30%)do not produce further refinement.With the increase of TiB_(2) content from 0 to 30%,the surface hardness of the coating increases from 530.5 HV to 738.4 HV,the fracture toughness decreases from 7.75 MPa·m^(1/2) to 3.17 MPa·m^(1/2),the wear rate decreases from 3.98 mg/mm^(2) to 0.42

关 键 词：激光熔化沉积 TIAL基合金 TiB_(2) 微观组织 力学性能 

分 类 号：TG174.4[金属学及工艺—金属表面处理]