Proces direktnega nanašanja kovinske žice z uporabo anularnega laserskega žarka : doktorsko delo

slovenian

doktorska dela

2021

annular laser beam   clad geometry   direct laser wire deposition   diserstations   process stability   workpiece irradiation proportion

Univerza v Ljubljani, Fakulteta za strojništvo
(Obvezni izvod spletne publikacije)

The process of direct laser wire deposition (DLWD) is often used for metal additive manufacturing due to its advantages. In this doctoral thesis, we examined the influence of process parameters on the stability of the annular laser beam (ALB) direct wire deposition process. Usage of the ALB enables coaxial wire feeding and symmetrical and simultaneous irradiation of the wire-end and the workpiece surface in different proportions, which is evaluated with a new process parameter, the workpiece irradiation proportion (WIP). To characterize the DLWD process, the initial and stationary phases of the process were studied and clad geometry was analyzed. It was shown that the precise synchronization of mutually-dependent laser beam power and wire and workpiece feeding velocity is required for process initialization. The most robust initial phase and stable transition into the stationary phase of the process was achieved with the initial wire-end position on the workpiece surface. At the selected wire and workpiece feeding velocities, initial and stationary laser beam power are nonlinearly dependent on the WIP. Improper process parameters result in either pending droplet formation or collision between the wire-end and the workpiece surface. The WIP also affects clad geometry, where higher WIP results in a lower dilution ratio which is linearly correlated with the workpiece and melt pool temperatures. Phenomenological characterization of the process showed that complex effects of process parameters on process stability and clad geometry are in addition to effective WIPE related to numerous physical phenomena, including laser beam reflection, heat transfer, and Marangoni flow in the melt pool.

15.05.2023