Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire

Abstract

This study investigates the influence of resistive pre-heating of the feedstock wire (here called hot-wire) on the stability of laser-directed energy deposition of Duplex stainless steel. Data acquired online during depositions as well as metallographic investigations revealed the process characteristic and its stability window. The online data, such as electrical signals in the pre-heating circuit and images captured from side-view of the process interaction zone gave insight on the metal transfer between the molten wire and the melt pool. The results show that the characteristics of the process, like laser-wire and wire-melt pool interaction, vary depending on the level of the wire pre-heating. In addition, application of two independent energy sources, laser beam and electrical power, allows fine-tuning of the heat input and increases penetration depth, with little influence on the height and width of the beads. This allows for better process stability as well as elimination of lack of fusion defects. Electrical signals measured in the hot-wire circuit indicate the process stability such that the resistive pre-heating can be used for in-process monitoring. The conclusion is that the resistive pre-heating gives additional means for controlling the stability and the heat input of the laser-directed energy deposition.

Wire Laser Metal Deposition Additive Manufacturing of Duplex Stainless Steel Components—Development of a Systematic Methodology

“…Wire pre-heating, in addition, improves process stability and minimizes the risk of formation of lack of fusion defects. More details about the single-bead deposits can be found in [ 3 ].…”

“…The results of the first and second stages were investigated in [ 3 , 4 ], and full details of the studies of the block produced in stage 3 and the cylinder produced in stage 4 will be within the scope of separate publications. In this paper, the application of the systematic methodology is presented, and examples of microstructures, chemical compositions, and mechanical properties leading up to the cylinder as the final components are presented.…”

“…The hot-wire control system aims to maintain a specific resistance to ensure a stable metal transfer, good wettability, and dimensional control. More details about the LMDw setup can be found in [ 3 ].…”

“…Laser Metal Deposition with Wire (LMDw) is an AM technique in which the wire is melted with a laser beam and deposited layer-by-layer (bead-by-bead) to build a component. In LMDw, the implementation of a laser beam in combination with an advanced controlling system allows appropriate monitoring and control of the process [ 3 , 4 ]. In addition to the low cost of raw material (the wire) [ 5 ] and high material usage efficiency (up to 100%), LMDw has provided the opportunity to reach comparatively high productivity [ 6 ] and is, therefore, suitable for the production of full-size near-net-shape parts for industrial applications.…”

“…In addition to the low cost of raw material (the wire) [ 5 ] and high material usage efficiency (up to 100%), LMDw has provided the opportunity to reach comparatively high productivity [ 6 ] and is, therefore, suitable for the production of full-size near-net-shape parts for industrial applications. Preheating the wire feedstock using the hot-wire technique can be used to further increase the deposition rate of LMDw [ 3 ], thereby improving productivity.…”