TC4激光熔覆Gd元素YSZ热障涂层微观特性研究

通过在钛合金表面引入稀土氧化物改性“7YSZ”即7 wt%氧化钇稳定的氧化锆涂层,提升传统热障涂层的综合性能。采用预制法并应用YLS-3000型光纤激光系统利用激光熔覆技术在TC4钛合金表面制备了不同Gd2O3添加量的Gd-YSZ涂层,通过光学显微镜、扫描电镜及能谱仪、X射线衍射仪和硬度仪分别表征涂层的宏观形貌、显微形貌、元素分布及相结构、硬度分布。引入的Gd以富稀土第二相Al3Gd及氧化物形式存在,并少量固溶于ZrO2和α-Ti晶格引发其晶格畸变而提升材料隔热性能,稀土Gd会抑制有害相TiOx而促进增强相TiC析出并优化其分布,并通过细化晶粒及优化TiC生长来提升组织显微硬度,Gd引入量增至10 wt%时这种优化作用被显著削弱。在7YSZ熔覆材料体系中掺杂Gd2O3能够显著提升材料综合性能,其添加量为影响性能的关键因素,不应超过10 wt%,否则会粗化晶粒,使Gd偏析、富集在晶界处,恶化材料性能。

Experimental study on microscopic characteristics of laser cladding Gd element YSZ thermal barrier coating on TC4 alloy

To improve the comprehensive performance of traditional thermal barrier coatings,introducing the rare earth oxides modified"7YSZ",which is 7wt%yttria-stabilized zirconia coating,on the surface of a titanium alloy.The Gd-YSZ coating with different Gd2O3 content was prepared on TC4 titanium alloy by laser cladding technology with yls-3000 fiber laser system.The macroscopic feature,microstructure,element distribution,phase structure and microhardness distribution of the coating were characterized by optical microscope,SEM,EDS,XRD and hardness tester respectively.The introduced Gd exists in the form of the rare earth-rich second phase Al3Gd and oxide,and a small amount of solid solution in ZrO2 andα-Ti lattice leads to lattice distortion,improves the thermal insulation performance of the material.Rare earth Gd can inhibit the harmful phase TiO2 and promote the reinforced phase TiC precipitation and optimize its distribution.The microhardness of the microstructure can be improved by refining the grains and optimizing the growth of TiC,the optimization effect is significantly weakened when the amount of Gd is increased to 10wt%.Doping Gd2O3 in 7YSZ cladding material system can significantly improve the comprehensive properties of the material,the amount of Gd2O3 is the key factor affecting the properties,which should not exceed 10 wt%,otherwise the grains will be coarsened,resulting in the Gd segregates and accumulates at the grain boundary,which deteriorates the properties of the materials.