Abstract
In this study, direct laser deposition (DLD) of nickel-based superalloy powders (Inconel 625) on structural steel (42CrMo4) was analysed. Cladding layers were produced by varying the main processing conditions: laser power, scanning speed, feed rate, and preheating. The processing window was established based on conditions that assured deposited layers without significant structural defects and a dilution between 15 and 30%. Scanning electron microscopy, energy dispersive spectroscopy, and electron backscatter diffraction were performed for microstructural characterisation. The Vickers hardness test was used to analyse the mechanical response of the optimised cladding layers. The results highlight the influence of preheating on the microstructure and mechanical responses, particularly in the heat-affected zone. Substrate preheating to 300 °C has a strong effect on the cladding/substrate interface region, affecting the microstructure and the hardness distribution. Preheating also reduced the formation of the deleterious Laves phase in the cladding and altered the martensite microstructure in the heat-affected zone, with a substantial decrease in hardness.
Highlights
The laser-based additive manufacturing (LBAM) technologies applied in the production and repair of industrial components emerged in the late 1990s
The quality of cladding was first evaluated by inspection with a digital microscope (DM)
scanning electron microscopy (SEM) characterisation confirmed the observations made by the DM
Summary
The laser-based additive manufacturing (LBAM) technologies applied in the production and repair of industrial components emerged in the late 1990s. The use of nickel-based superalloys in DLD must consider the high cooling rates of the process, promoted by the localised thermal delivery induced by the laser beam, which can lead to the formation of metastable phases and the segregation of elements. These microstructural effects reduce the toughness and hardness of the coated components [16,17,18,19]. Single layers were produced to evaluate the metallurgical bonding with a substrate; the influence of several processing parameters, such as laser power, scanning speed, and powder feed rate on the cladding quality, was evaluated considering the absence of cracks and structural imperfections.
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