The shape complexities of aerospace components are continuously increasing, which encourages industries to refine their manufacturing processes. Among such processes, the selective laser melting (SLM) process is becoming an economical and energy efficient alternative to conventional manufacturing processes. However, dependant on the component shape, the high surface roughness observed with SLM parts can affect the surface integrity and geometric tolerances of the manufactured components. To account for this, laser polishing of SLM components is emerging as a viable process to achieve high-quality surfaces. This report details an investigation carried out to understand the basic fundamentals of continuous wave laser polishing of SLM samples. A numerical model, based on a computational fluid dynamic formulation, was used to assist the understanding of melt pool dynamics, which significantly controls the final surface roughness. The investigation identified the input thermal energy as the key parameter that significantly affect the melt pool convection, and essentially controls the surface quality. Minimum meltpool velocity is essential to achieve wider laser polished track width with good surface finish. Experimental results showed a reduction of surface roughness from 10.2 μm to 2.4 μm after laser polishing with optimised parameters. Strategies to control the surface topology during laser polishing of SLM components are discussed

Laser‐powder bed fusion (L‐PBF) is extensively adopted in the aerospace and automobile industries for producing metallic components. The L‐PBF process involves rapid melting and solidification of metallic powders using a laser source to produce dense parts. Most industrial L‐PBF systems use a fiber‐based laser source that emits a Gaussian beam distribution. However, the conventional Gaussian beam used in L‐PBF processes presents inherent limitations that can impact the quality and properties of the final products. This review aims to provide a theoretical background of laser beam shaping techniques and explores the application of alternative beam shapes in L‐PBF. It investigates how different beam profiles affect the melt pool geometry, process stability, productivity, mechanical properties, microstructure, and surface roughness of fabricated parts. Additionally, it discusses different types of beam shaping techniques and elements utilized to generate distinct beam shapes. Furthermore, different constraints and limitations that hinder the full exploitation of beam shaping are critically discussed. By analyzing the impact of beam shaping in L‐PBF, this review provides insight into optimizing the additive manufacturing process, enhancing part quality, and improving processing performance. It will also help readers to overview the research gaps, challenges, and promising future directions in laser beam shaping applications in L‐PBF.

Micro-patterns with a single roughness were fabricated using a nanosecond laser source on stainless steel sheets to demonstrate a tunable and durable lotus effect via a vacuum process in a very short time interval. The wettability transitions of the vacuum processed μ-patterns were measured using the static water contact angle and found to be in the Cassie–Baxter state. The roll-off and static contact angle are 5° and 180°, respectively, for the μ-pillar and μ-channel structures. The surface exhibits bouncing and rolling of water droplets due to the composite interface. The transition of the wetting properties is a function of the vacuum process time and the minimum time required for the transition from ultrahydrophilic to ultrahydrophobic is found to be 15 minutes. The surface chemical analysis by XPS suggests that the chemisorption of hydrocarbon molecules onto hydroxylated metal oxide surfaces is much more effective under high vacuum than under an air atmosphere, due to the very low water vapor content inside the vacuum chamber, which avoids the passivation of reactive OH sites by hydrogen bonded water molecules. The wetting properties can be recycled by alternate plasma cleaning and vacuum processing of the laser-patterned surface.

This paper was accepted for publication in the journal Journal of Materials Processing Technology and the definitive published version is available at http://dx.doi.org/10.1016/j.jmatprotec.2015.05.005.A three-dimensional multiphase computational fluid dynamic model was developed to investigate the meltpool fluid dynamics, dilution and alloy composition in laser welding of low carbon steel and stainless steel. Using the developed model, independent predictions on weld properties are made for a range of laser parameters, and in all cases the results of the numerical model were found to be in close agreement with experimental observations. The investigation revealed that above certain specific point energy the materials within the melt pool are predominantly homogenous. A minimum meltpool convention is required in dissimilar laser welding to obtain weld bead properties suitable for industrial applications. The present model provides a simple yet effective method to predicting the weld bead alloying concentration and homogeneity encompassing wide range of materials