The effect of diode laser beam shape and traverse direction on the direct metal deposition process

Abstract

The use of CO2 and Nd:YAG lasers for Direct Metal Deposition (DMD) has mainly focussed on using a circular laser beam. However, the use of the more energy efficient high powered diode laser (HPDL) allows multiple layer cladding to be performed with a rectangular beam, traversed at different angles to the fast axis, or with a circular beam with even intensity distribution. These factors may all have an advantage, so there is a need to investigate the effect that they have on the process and final product characteristics. This paper reports such an investigation. The dimensions, microstructure, surface finish and hardness of multiple layer walls produced using a 1.5 kW HPDL and 316L stainless steel powder produced using rectangular and circular beams under a range of conditions are compared. Results show little difference in the microstructural and physical properties due to beam shape or traverse direction, but track dimensions are dependent on beam geometry. Wall width is particularly dependent on beam size orthogonal to the traverse direction. Fibre coupling seems to provide a benefit if even thin wall dimensions are required, while using the rectangular beam provides advantages for bulk material addition.