热喷涂Cr/Al2O3复合粉末的制备及性能研究

目的获得热喷涂用包覆型Cr/Al_2O_3复合粉末的制备工艺,探究工艺参数对热喷涂粉末结构及性能的影响规律。方法将纳米Al_2O_3水分散液与粘结剂混合润湿形成胶状液体,然后使其在核心粒子Cr表面团聚直接得到陶瓷相包覆金属相的复合颗粒,确定最佳制备工艺参数,并通过扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射(XRD)和霍尔流速与松装密度计研究工艺参数对复合粉末结构和性能的影响。结果在核-壳结构复合粉末制备过程中,加入一定量的粘结剂和减少包覆次数可以改善包覆效果,最终制得的包覆型颗粒壳层厚度可以达到25μm。随着Cr含量的增大,包覆效果有所下降,但粉末流动性变好,松装密度值提高。初始Cr粒度增大,包覆效果增强,颗粒球形度改善,但流动性和松装密度变化不大。结论机械包覆Cr/Al_2O_3复合粉末的最佳制备工艺参数为加入质量分数为5%的粘结剂进行一次包覆,该方法制得的复合粉末粒度分布均匀,流动性和松装密度值良好,适合热喷涂。

Preparation and Properties of Thermal Sprayed Cr/Al2O3 Composite Powder

The work aims to obtain preparation technology of coated Cr/Al2O3 composite powder for thermal spraying use, and investigate the rule of influence of process parameters on structure and properties of composite powder. Nano-alumina aqueous dispersion was mixed with the binder to form colloidal liquid, composite particles of which metallic phase was covered by ceramic phase from nano-alumina agglomerated around the core particles Cr. Optimal preparation process parameters were determined. Effects of process parameters on structure and properties of composite powder were studied with SEM, EDS, XRD and Hall flow meter. Adding some binder and reducing coating times could improve coating effect in the preparation process of core-shell structure. Thickness of the shell of final coated particle was up to 25 µm. With the increase of Cr content, the coating effect decreased while powder fluidity and apparent density improved. With the increase of initial Cr particle size, the coating effect and sphericity increased while liquidity and apparent density change slightly. Adding 5wt% binder for coating one time is the best preparation process parameters of coating Cr/Al2O3 composite powder, the powder prepared in this manner features in uniform particle size, good flow ability and apparent density, hence it is suitable for thermal spraying.