两步法制备纳米TiC_(p)/GH3536复合粉末组织性能研究

Microstructure and properties of nano-TiC_(p)/GH3536 composite powders prepared by two-step method

采用机械合金化(mechanical alloying, MA)结合热等离子体球化处理(thermal plasma spheroidization,TPS)两步法,制备纳米TiC_(p)/GH3536复合粉末。采用霍尔流速计、斯科特容量计、XRD、粒度粒形仪、扫描电子显微镜及透射电子显微镜等分析测试手段,研究球化处理前后复合粉末的流动性、松装密度、粒度分布、球形度及微观组织形貌。结果表明:第一步MA-5 h处理得到的预制粉末为基体GH3536表面非均匀附着纳米TiC颗粒的不规则形状粉末;相比原始GH3536粉末,预制粉末内部等轴晶数量增多,晶粒得到细化,但流动性和松装密度均降低。第二步TPS处理得到的纳米TiC_p/GH3536复合粉末为球形,原始不规则纳米TiC颗粒被球化,同时均匀分布于GH3536基体内部;去除平均粒度183.27 nm的亚微米颗粒后,复合粉末的流动性、松装密度和球形度得到进一步改善。亚微米颗粒的TEM结果显示,纳米级GH3536微球上均匀包覆着一层TiC,类似核壳结构,且粉末中出现球状TiC颗粒。两步法制备的纳米TiC_(p)/GH3536复合粉末,平均球形度达0.965,平均粒径为33.65μm,流动性为17.1 s/50 g,松装密度为4.184 g/cm^(3)。

Nano-TiC_(p)/GH3536 composite powders were prepared by mechanical alloying(MA)and thermal plasma spheroidization(TPS)methods.The flowability,bulk density,particle size distribution,sphericity,and microstructure of the composite powders before and after MA-TPS treatment were studied by Hall flow meter,Scott volumeter,XRD,particle size analyzer,scanning electron microscope,and transmission electron microscope.The results show that the preformed powders obtained by MA-5 h treatment are irregular shape powders with non-uniform adhesion of nano-TiC particles on the surface of the GH3536 substrate.Compared with the original GH3536 powders,the number of equiaxed grains in the preformed powders increases and the crystal grains are refined,but the flowability and bulk density decrease.The nano-TiC_(p)/GH3536 composite powders obtained by the second TPS treatment are spherical,and the original irregular nano-TiC particles are spheroidized and uniformly distributed inside the GH3536 substrate.After removing the submicron particles with an average particle size of 183.27 nm,the flowability,bulk density,and sphericity of TPS composite powders are further improved.The TEM images of submicron particles show that the nanoscale GH3536 microspheres are uniformly coated with a layer of TiC,the structure is similar to the core-shell,and spherical TiC particles are found in the powder.The average spherical degree,average particle size,flowability,and bulk density of the nano-TiCp/GH3536 composite powders prepared by the two-step method are 0.965,33.65μm,17.1 s/50 g,and 4.184 g/cm3,respectively.