Process Planning for Additive Manufacturing of Geometries with Variable Overhang Angles using a Robotic Laser Directed Energy Deposition system

In the present work, a novel Laser Directed Energy Deposition (LDED) process planning methodology is proposed to build a dome structure with variable overhang angles. Overhang structures with different overhang angles were built where the maximum angle of 35° can be used to build overhang structures without the process and structure compromise. The thin-wall hemispherical dome built using the developed methodology shows the maximum deviation of 2% with respect to the diameter of the original CAD model data. The study paves a way for building high-value, lightweight thin-walled structures with complex cylindrical-based shape (e.g., storage tanks, nozzles, combustion chambers) for engineering applications.Federal development of Ontario (Fed-Dev) || Promation Engineering

Studies on the Effect of Laser Shock Peening Intensity on the Mechanical Properties of Wire Arc Additive Manufactured SS316L

This study examines the impact of laser shock peening (LSP) on the mechanical properties, microstructural features, and elemental distribution of stainless steel 316L (SS316L) produced using wire arc additive manufacturing (WAAM). The investigation focuses on significant changes in mechanical behavior, surface topography, and porosity following LSP treatment, comparing these results to the untreated condition. LSP treatment significantly enhanced the ultimate tensile strength (UTS) and yield strength (YS) of WAAM-fabricated SS316L samples. The UTS of the as-manufactured WAAM specimen was 548 MPa, which progressively increased with higher LSP intensities to 595 MPa for LSP-1, 613 MPa for LSP-2, and 634.5 MPa for LSP-3, representing a maximum improvement of 15.8%. The YS showed a similar trend, increasing from 289 MPa in the as-manufactured specimen to 311 MPa (LSP-1) and 332 MPa (LSP-2), but decreasing to 259 MPa for LSP-3, indicating over-peening effects. Microstructural analysis revealed that LSP induced severe plastic deformation and reduced porosity from 14.02% to 4.18%, contributing to the improved mechanical properties. Energy dispersive spectroscopy (EDS) analysis confirmed the formation of an oxide layer post-LSP, with an increase in carbon (C) and oxygen (O) elements and a decrease in chromium (Cr) and nickel (Ni) elements on the surface, attributed to localized pressure and heat impacts. LSP-treated samples exhibited enhanced mechanical performance, with higher tensile strengths and improved ductility at higher laser intensities. This is due to LSP effectively enhancing the mechanical properties and structural integrity of WAAM-fabricated SS316L, reducing porosity, and refining the microstructure. These improvements make the material suitable for critical applications in the aerospace, automotive, and biomedical fields

Laser Directed Energy Deposition-Based Additive Manufacturing of Fe20Cr5.5AlY from Single Tracks to Bulk Structures: Statistical Analysis, Process Optimization, and Characterization

Laser directed energy deposition (LDED) can be deployed for depositing high-performance materials for various engineering applications. Alumina-forming steel is a high-performance material that possesses excellent corrosion and oxidation resistance, finding application in the power generation sector. In the present work, LDED using powder feeding (LDED-PF) was used to deposit Fe20Cr5.5AlY alloy using single-track, multi-track, and multi-layer deposition on SS 316L substrate. Response surface methodology (RSM)-based optimization was used to optimize the single-track deposition. The relationship between the track geometry parameters and the build rate with the LDED-PF processing parameters was studied. Further, the nonlinear relationship among the major process parameters was developed and an analysis of variance (ANOVA) was utilized to find significant parameters. The multi-track deposition yielded densely clad layers with a columnar grain structure. The presence of complex oxide slag of Y, Al, and Zr on the clad layer was detected. A micro-hardness of 240–285 HV was observed in the clad layer, with a hardness of 1088–1276 HV at the slag layer. The multi-layered structures showed a relative density of 99.7% with columnar growth and an average microhardness of 242 HV. The study paves the way for the deposition of dense alumina-forming steel structures for building components for power generation applications

A review on fabrication of 3D printed biomaterials using optical methodologies for tissue engineering applications

Human body comprises of different internal and external biological components. Human organs tend to fail due to continuous or sudden stress which leads to deterioration, failure, and dislocation. The choice of selection and fabrication of materials for tissue engineering play a key role in terms of suitability, sensitivity, and functioning with other organs as a replacement for failed organs. The progressive improvement of the additive manufacturing (AM) approach in healthcare made it possible to print multi-material and customized complex/intricate geometries in a layer-by-layer fashion. The customized or patient-specific implant fabrication can be easily produced with a high success rate due to the development of AM technologies with tailorable properties. The structural behavior of 3D printed biomaterials is a crucial factor in tissue engineering as they affect the functionality of the implants. Various techniques have been developed in appraising the important features and the effects of the subsequent design of the biomaterial implants. The behavior of the AM built biomaterial implants can be understood visually by an imaging system with a high spatial and spectral resolution. This review intends to present an overview of various biomaterials used in implants, followed by a detailed description of optical 3D printing procedures and evaluation of the performance of 3D printed biomaterials using optical characterization. </jats:p

Preliminary Parametric Investigations into Macro-Laser Polishing of Laser-Directed Energy Deposition of SS 304L Bulk Structures

The higher surface roughness of laser-directed energy deposition (LDED)-built components necessitates advanced and sustainable surface quality enhancement techniques like laser polishing. In the present work, a parametric study involving experimental investigation and numerical analysis is conducted to determine the effect of macro-laser polishing on LDED-built SS 304L structures. A thermophysical model is developed to simulate the effect of laser power and scan speed on the melt pool depth of the LDED-built samples. The simulated melt pool depth is compared with experimental results and is found to be in good agreement. Further, the correlation between the melt pool depth and surface behaviour is studied based on shallow surface melting and shallow over-melting mechanisms. A maximum reduction in surface roughness from 21.3 µm to 9 µm (~57%) is achieved with laser polishing, and process parameters’ effect on the surface roughness is investigated. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) mapping, and X-ray diffraction (XRD) are used to further characterize the laser-polished surface. SEM-EDS analysis shows that the segregation is more evident in laser-polished samples, while the XRD results indicate the absence of phase change during the process. This study paves the way to a greater understanding of the effect of macro-laser polishing on LDED-built SS 304L structures

Elucidating sequential laser remelting in tailoring microstructure and mechanical performance of laser-directed energy deposited Hastelloy-X

The current manuscript undertakes a systematic analysis of sequential layer-by-layer laser remelting (SLLR) within the context of laser-directed energy deposition (LDED) of Hastelloy-X (HX) bulk structures. Comparative analysis is conducted between the surface and bulk properties of LDED-built samples and those incorporating SLLR. Integrating SLLR with LDED results in a notable decrease in surface roughness by 71.5% and porosity by eight times. While both lack of fusion and gas porosity are evident in the as-built sample, the combination of SLLR with LDED shows only gas porosity. Moreover, microstructural refinement is observed after SLLR without preferential growth along (100), unlike in samples without SLLR. Analysis reveals segregations of Mo, Si, and C and the presence of Mo-rich carbides in both LDED and SLLR samples. The finer dendritic microstructures observed in SLLR samples contribute to a 12% increase in microhardness and a 7% rise in yield strength along the build direction compared to samples without SLLR. This study lays the path for fabricating dense components with tailored microstructures and mechanical properties during LDED through the utilisation of SLLR