Capturing droplet flight and impingement behavior in plasma–MIG process for metal droplet-on-demand applications
Angshuman Kapil, Nithin Kayarthaya, Vatsalya Sharma, Abhay Sharma
Abstract
On-demand metal droplet deposition has garnered increased interest in recent years owing to its potential applications in additive manufacturing. Plasma metal inert gas droplet deposition (plasma MIG DD), a unique variant of plasma MIG welding, allows the deposition of individual droplets with high accuracy, minimal melting of the substrate, and minimal spatter and metal fume generation. This study develops an in-depth understanding of both the process physics and the droplet dynamics through the development of a computational fluid dynamics-based multiphase simulation methodology. The investigation elucidates the droplet flight, and post-impingement droplet spreading, cooling, and solidification behavior for different initial droplet temperatures and substrate materials. The final droplet morphology predicted by the simulation agrees well with experimental results (error≤10%). The study reveals that post-impingement droplet behavior is dependent on both the initial droplet temperature and the material properties of the substrate. When a copper droplet impinges on a copper substrate, it attains a spherical shape with a small contact surface. On the other hand, when a copper droplet impinges on an aluminum substrate, it takes a more flattened shape with a smaller contact angle and higher contact area. The maximum spread of the droplet post-impingement is higher for the aluminum substrate at all droplet temperatures. Higher penetration in the aluminum substrate compared to copper substrate indicated by the melting contours establishes its suitability for depositing copper droplets. The presented results are fundamental and provide a pathway for parametric optimization, process design, and reverse engineering for a wide array of droplet-on-demand applications.