Study of the Influence of Shielding Gases on Laser Metal Deposition of Inconel 718 Superalloy

Abstract

The use of the Laser Metal Deposition (LMD) technology as a manufacturing and repairing technique in industrial sectors like the die and mold and aerospace is increasing within the last decades. Research carried out in the field of LMD process situates argon as the most usual inert gas, followed by nitrogen. Some leading companies have started to use helium and argon as carrier and shielding gas, respectively. There is therefore a pressing need to know how the use of different gases may affect the LMD process due there being a lack of knowledge with regard to gas mixtures. The aim of the present work is to evaluate the influence of a mixture of argon and helium on the LMD process by analyzing single tracks of deposited material. For this purpose, special attention is paid to the melt pool temperature, as well as to the characterization of the deposited clads. The increment of helium concentration in the gases of the LMD processes based on argon will have three effects. The first one is a slight reduction of the height of the clads. Second, an increase of the temperature of the melt pool. Last, smaller wet angles are obtained for higher helium concentrations.

Analysis of Melt Pool Characteristics and Process Parameters Using a Coaxial Monitoring System during Directed Energy Deposition in Additive Manufacturing

“…The expression of a plasma plume is a known phenomenon when the carrier and shielding gas argon is used in combination with higher specific energy values. For example, Ruiz et al [11] varied the specific energy in the range of ESpec=15−30 normalJ/mm2 while building up single tracks of NiCr19NbMo. They suspected the argon to form an ionised gas because of its first ionisation energy of EIon=1520.8 kJ/mol.…”

“…To calculate the melt pool area (see Walter [10]) a threshold needed to be predefined, above which a pixel is counted to the melt pool area. Due to additional radiation from surface plasma [11,12], the threshold of 163 digits led to overexposed camera images. As an example, it is shown in Figure A2 that the characteristic of the temporally averaged number of pixels (NOP) over the laser power variation did not change with the threshold value.…”

“…In current practice, most suitable measurement systems work contactless and using optical technology [7]. Several studies [8,9,10,11] have shown that temperature distribution inside a melt pool, as well as its shape, contain information about process parameters. Meriaudeau et al [9] determined a decreasing melt pool surface temperature as an indicator for an increasing powder feed rate m˙.…”

Metal Matrix Composites Synthesized by Laser-Melting Deposition: A Review

“…Figure 3 classifies the process parameters: (a) controllable, and (b) uncontrollable parameters [ 62 ]. The controllable parameters can be tackled directly; however, the uncontrollable parameters can be adjusted indirectly through the controllable parameters [ 63 , 64 , 65 , 66 , 67 , 68 , 69 ].…”

“… Process Parameters in the LMD technique; based on the data provided in Ref. [ 2 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 ]. …”