Pulsed laser influence on temperature distribution during dual beam laser metal deposition

Abstract

Wire-based Laser Metal Deposition (LMD-w) is a suitable manufacturing technology for a wide range of applications such as repairing, coating, or additive manufacturing. Employing a pulsed wave (pw) laser additionally to the continuous wave (cw) process laser has several positive effects on the LMD process stability. The pw-plasma has an influence on the cw-absorption and thus the temperature distribution in the workpiece. In this article, several experiments are described aiming to characterize the heat input during dual beam LMD. In the first setup, small aluminum and steel disks are heated up either by only cw or by combined cw and pw radiation. The absorbed energy is then determined by dropping the samples into water at ambient temperature and measuring the water’s temperature rise. In a second experiment, the temperature distribution in the deposition zone under real process conditions is examined by two-color pyrometer measurements. According to the results, the pw plasma leads to an increase of the effective absorption coefficient by more than 20%. The aim of this work is to achieve a deeper understanding of the physical phenomena acting during dual beam LMD and to deploy them selectively for a better and more flexible process control.