Enhancment in deposition rate of laser DMD

Abstract

Direct metal deposition (DMD) has been developed as a manufacturing process to deposit coatings on existing materials. Among several DMD technologies, powder-based laser DMD proves advantageous in Additive Manufacturing (AM) of complex and precise components. However, the typical productivity rate of this technique is still not sufficient economically in the case of large parts fabrication. The intent of this dissertation is to address enhancement in productivity through different routes. First, the effects of the main laser process parameters on clad properties and build-up rate, as well as the strategy of process scaling, are studied. The constructed processing map presents the optimum combination of parameters to obtain depositing of well-bonded layers at the maximum deposition rate and powder melting efficiency. The developed approach and equations formulate the critical laser parameters and establish a link between the effect of these variables and clad geometry to generate appropriate parameter quantities for depositing material at a higher rate. In the next step, the coaxial hybrid Induction Heating DMD (IH-DMD) technique is presented. The elaborated finite element simulation model of electromagnetic IH supports the hybrid process by identifying a correlation between parameters and generated heating temperature. The results demonstrate the vital role of the magnetic flux concentrator, coupling gap, and electric current to achieve a required heating rate. By employing IH-DMD, the coating deposition improved by a factor of three. Approaches are presented to re-characterize the laser parameters to fabricate defects-free layers with this system. Finally, a combined method of laser DMD and Plasma Transferred Arc (PTA) is introduced. The joining strategy of dissimilar layers, as well as the microstructure, hardness, and tensile strength of the produced samples, are examined. The specifications analysis shows that both processes are capable of being integrated into one operating system to enhance the build-up rate. Accordingly, productivity can be improved by 2–5 times. The Layer-wise deposition of both processes presents a dense microstructure. The side-by-side deposition of layers requires proper joint strategy due to the broader track in the PTA compared to the DMD. The DMD layers exhibit higher hardness and tensile strength due to the smaller grain size.