NiTi气雾化制粉工艺对选区激光熔化成型性、制件超弹性的影响

Effect of NiTi Powder Gas Atomization Process on the Selective Laser Melting Moldability and Alloys’ Superelastic

选区激光熔化成型具有外界温度感知能力的NiTi形状记忆合金是4D打印金属材料技术的基础研究,根据选区激光熔化技术对粉末性能的要求,研究NiTi形状记忆合金不同气雾化制粉工艺对选区激光熔化成型性及制件超弹性的影响规律具有重要意义。通过对比分析真空惰性气体雾化(VIGA)、电极感应熔炼气雾化(EIGA)制粉工艺对NiTi合金粉末杂质含量、流动性、球形度等性能的影响,发现VIGA制粉工艺由于采用坩埚熔炼,导致合金杂质元素增加、粉体性能恶化,粉末粒度分布偏向细粉侧,极易形成卫星粉,导致粉末流动性差,在打印过程中铺粉困难而难以成型,并且氧含量的增加导致打印过程中易发生球化、开裂等现象,使得VIGA工艺制备的NiTi合金粉末SLM成型性较差。而采用EIGA工艺制备的粉末粒度分布均匀、流动性好、氧含量低,满足选区激光熔化技术对NiTi合金粉末的特性要求。并对比分析两种工艺制备的粉末打印样品的表面形貌,成型了具有完全回复性能的超弹NiTi形状记忆合金样件。

Selective laser melting NiTi shape memory alloy which has ambient temperature sensing capability is the basic of a metal material 4 D printing technology, according to the technical requirements for selective laser melting the powder properties, studying the effect of Ni Ti powder gas atomization process on the selective laser melting moldability and alloys’ superelastic is great significant. By comparing the influence of vacuum inert gas atomization(VIGA) and electrode induction melting gas atomization(EIGA) process on the performance of NiTi alloy powder, such as the impurity content, fluidity, spherical degree. The VIGA process which used crucible melting resulting in impurity content is higher than EIGA process, and fine powder size distribution biased side, easy to form satellite powder, resulting in poor powder flow, and powder spreading difficulties in the printing process and difficult to mold, more than of that, increasing the oxygen content results in balling in the SLM process, prone to cracking and so on, hence the NiTi alloy powder prepared by VIGA process is poor moldability in SLM process. EIGA prepared NiTi powder hold homogeneous particle size distribution, good fluidity and low oxygen content, satisfying selective laser melting technique NiTi alloy powder characteristics requirements. Comparison of surface topography and powder samples prepared from two printing processes, forming a superelastic NiTi shape memory alloy sample having a complete ecovery properties.