TiN含量对Ti_(0.8)CoCrFeNiAl_(0.5)高熵合金涂层组织与性能的影响

Effects of TiN Content on Microstructures and Properties of Ti_(0.8)CoCrFeNiAl_(0.5) High-Entropy Alloy Composite Coating

为进一步改善高熵合金Ti_(0.8)CoCrFeNiAl_(0.5)的硬度和耐磨性,利用激光熔覆技术在TC21钛合金表面制备不同TiN含量的Ti_(0.8)CoCrFeNiAl_(0.5)/TiN高熵合金复合涂层。采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、电子探针(EPMA)对熔覆层的显微组织、物相成分进行检测与分析,选用显微硬度计和材料表面综合性能测试仪对熔覆层的硬度分布和耐磨性能进行表征。试验结果表明,熔覆层无明显缺陷,呈良好的冶金结合。未添加TiN时,熔覆层主要由BCC1、FCC、Laves相、富β–Ti相等物相组成;添加TiN后,熔覆层主要由富Al–Co–Ni–Ti的BCC1相枝晶组织以及富Fe–Cr–Ti的BCC2相、Laves相、富β–Ti相组成的枝晶间组织与镶嵌在枝晶和枝晶间的TiN相构成。熔覆层的显微硬度均提高为基体的2倍以上,添加质量分数8%TiN熔覆层的硬度提高到未添加TiN熔覆层硬度的1.23倍。当TiN添加质量分数为6%时,熔覆层耐磨性较好,约为未添加TiN熔覆层的2.92倍。TiN的添加有利于促进熔覆层中BCC相的生成和TiN相析出,能有效提高熔覆层的硬度及耐磨性能。

The work aims to further enhance the microhardness and wear resistance of high-entropy alloy(HEA)Ti_(0.8)CoCrFeNiAl_(0.5).The Ti_(0.8)CoCrFeNiAl_(0.5)/TiN composite coatings with different TiN contents were prepared on the surface of TC21 by laser cladding.The microstructures and phases of cladding layer were analyzed with scanning electron microscopy(SEM),X–ray diffractometry(XRD)and electron probe microanalysis(EPMA).The hardness distribution and wear resistance of the cladding layer are characterized by the microhardness tester and the material surface comprehensive performance tester.The results showed that the cladding layer is formed well and has good metallurgical bonding.Without TiN,the cladding layer is mainly composed of BCC1,FCC,Laves phases andβ–Ti.After adding TiN,TiN particles precipitate in-situ in the cladding layer.The cladding layer is mainly composed of dendritic structure of BCC1 phase rich in Al–Co–Ni–Ti,interdendritic structure of BCC2 phase rich in Fe–Cr–Ti and Laves phase,β–Ti and TiN particles embedded between dendritic structure and interdendritic structure.The microhardness of the cladding layer increases to more than 2 times of the substrate,and the hardness of the cladding layer with 8%TiN is 1.23 times of the sample without TiN.When the content of TiN is 6%,the wear resistance is high,which is about 2.92 times that of the sample without TiN.It reveals that the addition of TiN is beneficial to the precipitation of TiN particles and the formation of BCC phase in the cladding layer,which can effectively improve the hardness and wear resistance of the cladding layer.