Material Response Of Semiconductors Irradiated With Ir Ultrashort Laser Pulses

We utilize near- and mid-IR ultrafast laser radiation to investigate the processing of crystalline silicon with different dopants. A numerical model is adopted to simulate the material response depending on the wavelength and the dopant concentration

Femtosecond Single-Pulse Absorption in Semiconductors with varying Dopant Concentration

The influence of dopant concentration on the absorption of femtosecond mid-IR pulses is described. The measured results are compared to a theoretical absorption model

Femtosecond Single-Pulse Absorption In Semiconductors With Varying Dopant Concentration

The influence of dopant concentration on the absorption of femtosecond mid-IR pulses is described. The measured results are compared to a theoretical absorption model. © Owned by the authors, published by EDP Sciences, 2013

Post-Processing Of 3D-Printed Parts Using Femtosecond And Picosecond Laser Radiation

Additive manufacturing, also known as 3D-printing, is a near-net shape manufacturing approach, delivering part geometry that can be considerably affected by various process conditions, heat-induced distortions, solidified melt droplets, partially fused powders, and surface modifications induced by the manufacturing tool motion and processing strategy. High-repetition rate femtosecond and picosecond laser radiation was utilized to improve surface quality of metal parts manufactured by laser additive techniques. Different laser scanning approaches were utilized to increase the ablation efficiency and to reduce the surface roughness while preserving the initial part geometry. We studied post-processing of 3D-shaped parts made of Nickel- and Titanium-base alloys by utilizing Selective Laser Melting (SLM) and Laser Metal Deposition (LMD) as additive manufacturing techniques. Process parameters such as the pulse energy, the number of layers and their spatial separation were varied. Surface processing in several layers was necessary to remove the excessive material, such as individual powder particles, and to reduce the average surface roughness from asdeposited 22-45 μm to a few microns. Due to the ultrafast laser-processing regime and the small heat-affected zone induced in materials, this novel integrated manufacturing approach can be used to post-process parts made of thermally and mechanically sensitive materials, and to attain complex designed shapes with micrometer precision. © 2014 SPIE

Characterization Of Lam-Fabricated Porous Superalloys For Turbine Components

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Inconel alloys remain the material of choice for most hot gas path components in gas turbines, however recent increases in turbine inlet temperature (TIT) are associated with the development of advanced convective cooling methods and ceramic thermal barrier coatings (TBC). Increasing cycle efficiency and cycle specific work are the primary drivers for increasing TIT. Lately, incremental performance gains responsible for increasing the allowable TIT have been made mainly through innovations in cooling technology, specifically convective cooling schemes. An emerging manufacturing technology may further facilitate the increase of allowable maximum TIT, thereby impacting cycle efficiency capabilities. Laser Additive Manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to manufacture designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex features found in turbine blades. A leading edge segment of a turbine blade, containing both internal and external cooling features, along with an engineered-porous structure is fabricated by laser additive manufacturing of superalloy powders. Various cooling features were incorporated in the design, consisting of internal impingement cooling, internal lattice structures, and external showerhead or transpiration cooling. The internal structure was designed as a lattice of intersecting cylinders in order to mimic that of a porous material. Variance distribution between the design and manufactured leading edge segment are carried out for both internal impingement and external transpiration hole diameters. Through a non-destructive approach, the presented geometry is further analyzed against the departure of the design by utilizing x-ray computed tomography (CT). Employing this non-destructive evaluation (NDE) method, a more thorough analysis of the quality of manufacture is established by revealing the internal structures of the porous region and internal impingement array. Flow testing was performed in order to characterize the uniformity of porous regions and flow characteristics across the entire article for various pressure ratios (PR). Discharge coefficient of internal impingement arrays and porous structure are quantified. The analysis yields quantitative data on the build quality of the LAM process, providing insight as to whether or not it is a viable option for manufacture of micro-features in current turbine blade production

Characterization Of Laser Additive Manufacturing-Fabricated Porous Superalloys For Turbine Components

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Lately, incremental performance gains responsible for increasing the allowable turbine inlet temperature (TIT) have been made mainly through innovations in cooling technology, specifically convective cooling schemes. Laser additive manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to manufacture designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex features found in turbine blades. A leading edge segment of a turbine blade, containing both internal and external cooling features, along with an engineered-porous structure is fabricated by laser additive manufacturing of superalloy powders. Through a nondestructive approach, the presented geometry is analyzed against the departure of the design by utilizing X-ray computed tomography (CT). Variance distribution between the design and manufactured leading edge segment are carried out for both internal impingement and external transpiration hole diameters. Flow testing is performed in order to characterize the uniformity of porous regions and flow characteristics across the entire article for various pressure ratios (PR). Discharge coefficients of internal impingement arrays and engineered-porous structures are quantified. The analysis yields quantitative data on the build quality of the LAM process, providing insight as to whether or not it is a viable option for direct manufacture of microfeatures in current turbine blade production

Femtosecond Laser Post-Processing Of Metal Parts Produced By Laser Additive Manufacturing

High-repetition rate femtosecond laser radiation was utilized to improve surface quality of metal parts manufactured by laser additive techniques. This novel approach can be used to postprocess parts made of heat-sensitive materials, and to attain the designed net shape with micrometer precision. © Owned by the authors, published by EDP Sciences, 2013

Lasers For Ultrafast Laser-Materials Processing

Nearly all advances made in processing materials in the fs (\u3c 100 fs) domain have so far been achieved with the use of Ti:Sapphire lasers at a wavelength of 800 nm. For longer pulses (\u3c 1 ps), lasers operating at 1 μm have played an important role. Whereas the latter might be considered for industrial or manufacturing environments, Ti:Sapphire lasers have several disadvantages. With knowledge and expertise in the processing of many different categories ofmaterials over a wide range of processing parameters, we review the different effects that can be created with ultrafast laser pulses from the viewpoint of the optimum laser performance. Beginning from an understanding of the fundamental processes involved in ultrafast laser-materials interaction, we survey the different effects that can be created, from nanostructuring, to bond-modification, refractive index modification, localized changes in density, microcrystallization, and the various mechanisms involved in ablation, and then discuss the impact of the laser parameters used and the processing optics involved.With a knowledge of the new technologies that will influence the development of tomorrow’s ultrafast lasers, those that are compact, efficient, cost-effective, and deployable in workspace environments, we identify those processing technologies that will be viable first to enter future markets