Establishment of Three-Dimensional Reactive-Freeform Processing for Auminide Intermetallics

本研究的目的是开发新的三维微焊接方法，使其能够自由成形耐热、耐蚀、耐磨但制造和加工困难的铝化物金属间化合物、难熔金属和合金。我们的目标是在未来建立3DMW和IT技术相结合的远程制造工艺。主要研究成果如下：1.在世界上首次开发了可自由成形致密铝化物金属间化合物等难熔金属的三维微细焊接技术。2.在直径约200μm的细丝顶端放弧形成熔融的微细金属珠，形成三维立体结构的计算机辅助设计/计算机辅助制造系统。我们已经成功地形成了钛、镍、钽、钛镍、镍钛合金微珠及其简单的三维物体。通过在3DMW系统中交替提供两种不同的金属丝，实现了NiAl和TiNi等自由形态金属间化合物的同时合成。4.通过在金属基片表面形成微熔池和吹氮气，在3DMW上增加了金属氮化物层的形成功能。此外，通过移动放电电极，在小熔池中提供一根细长的铝丝，在金属表面制备了铝化物涂层。用这些方法在钛和TiAl上进行了TiN涂层，在Nb上进行了NbN涂层。在Nb表面也形成了NbAl_3层。这些涂层在硬度、耐磨性和抗氧化性方面都有显著的提高，通过本研究可以建立耐热、耐磨、耐腐蚀物体的自由成形和涂层的基本工艺。

The objective of this research is to develop new three-dimensional micro-welding methods being enable to freeform aluminide intermetallics, refractory metals and alloys which are superior in heat, corrosion and wear resistances, but difficult in manufacturing and machining. We aim to establish the remote fabrication process by combining 3DMW and IT technology in future. The obtained results are summarized as follows.1.3D micro-welding which can freeform dense aluminide intermetallics and other refractory metal objects has been first developed in the world.2.It is a CAD/CAM system to form molten micro metal beads by discharging arc to the tip of a thin metal wire with around 200μm in diameter and build up three dimensionally. We have succeeded in formation of Ti, Ni, Ta, TiNi, inconel beads, and their simple 3D objects. The morphology, composition, and microstructure of beads were also investigated.3.It was demonstrated to synthesize and simultaneously freeform intermetallics such as NiAl and TiNi by providing two different wires alternately in 3DMW system.4.We added a function of metal nitride layer formation to 3DMW by producing a micro molten pool at the surface of a metal substrate and blowing nitrogen gas. Furthermore, by moving a discharging electrode and providing a thin aluminum wire to the small molten pool, the aluminide coating was prepared on the metal surface. By these methods, TiN coating on Ti and TiAl, and NbN on Nb were performed. The NbAl_3 layer was formed on Nb as well. These coatings showed remarkable improvements in hardness, wear and oxidation resistances.We could establish the basic technology of freeforming and coating of heat, wear, corrosion resistant objects by this research.