In the present study, Inconel 718 (IN718) superalloy fabricated by laser powder bed fusion (LPBF) has been characterized focusing on the effect of both homogenization and solution treatment time on grains structure, crystallographic texture, precipitates formation/dissolution and material hardness. For this purpose, a heat-treatment time window with a wide range of soaking times for both treatments was established aiming to develop the optimal post-treatment conditions for laser powder bed fused IN718. It was found that the as-printed IN718 is characterized by very fine columnar/cellular dendrites with Laves phase precipitating at the grain boundaries as well as inter-dendritic regions, which differs from the microstructure of wrought and cast materials and requires special heat-treatment conditions different from the standard treatments. The results reveal that the relatively short homogenization treatment at 1080 °C for 1 h was not enough to significantly change the as-printed grain structure and completely dissolve the segregates and Laves phase. However, a completely recrystallized IN718 material and more Laves phase dissolution were obtained after homogenization treatment for 4 h. A further increase in time of the homogenization treatment (7 h) resulted in grain growth and coarsening of carbides precipitates. The solution treatment time at 980 °C did not cause noticeable changes in the crystallographic texture and grain structure. Nevertheless, the amount of δ-phase precipitation was significantly affected by the solution treatment time. After applying the heat-treatment time window, the hardness increased by 51–72% of the as-printed condition depending on the treatment time due to the formation of γ′ and γ″ in the γ-matrix. The highest material hardness was obtained after 1 h homogenization, whereas the prolonged time treatments reduced the hardness. This study provides a comprehensive investigation of the post heat-treatments of the laser powder bed fused IN718 that can result in an optimized microstructure and mechanical behavior for particular applications.

Direct selective laser sintering (SLS) is an additive manufacturing technique for the fabrication of near net shaped parts directly from computer-aided design data by sintering together different layers with the help of a laser source. This paper presents an investigation of the physical properties (density and porosity) of alumina (Al2O3) samples produced by SLS. Some input parameters, namely laser power and scan speed were selected for the investigation. The aim of this work is to understand the effect of these sintering parameters on the quality of the sintered layer (surface roughness), physical properties (density and porosity) and microstructure (grain size) are investigated. The results showed that maximum density of the sintered ceramics layers are of 3.54 gm/cm3 and minimum porosity of 4.34% were obtained at laser power 230 W and laser scanning speed 150 mm/min. The morphology was analyzed by means of field emission scanning electron microscope. Laser power and Scan speed were found to have a great influence on the surface roughness and morphology.

Selective laser sintering processes is one of the most additive manufacturingprocesses. This process characterized by its interaction parameters and their severinfluence in the process output. The most significant parameters were found to be laserpower, laser scanning speed. The main objectives of this work are to understand theeffect of these parameters and their interaction on the process quality and physicalproperties of ceramic laser-sintered components; and to introduce a statistical modelthat assist in determining the optimal values of the significant parameters andprediction of corresponding sintering responses, aiming reduce the consumed time formanufacturing and consequently the cost of the component. Experiments were carriedout using a pulsed Nd: YAG laser machine. Design of experiments and statisticalmodeling techniques were employed using response surface methodology. The effectsof the two controllable variables, laser power, laser scanning speed and theirinteraction on the laser sintered line width, monolayer thickness, surface roughnessand density were investigated. The results indicate that the developed model canpredict the responses adequately within the limits of sintering parameters being used.