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Laser Engineered Net-Shaping (LENS®) is an emerging manufacturing technique that ensures significant reduction of process time between initial design and final components. The fabrication of fully dense parts with appropriate properties using the LENS® process requires an in-depth understanding of the entire thermal behavior of the process. In this paper, the thermal behavior during LENS® was studied, both numerically and experimentally. Temperature distribution and gradient in the fabricated part were obtained by finite element method (FEM) simulation. The numerical results are in good agreement with the experimental observations. The numerical method may be used to optimize process parameters and predict the thermal response of LENS® fabricated components.

Direct fabrication (DF) of tool and die steels by rapid solidification techniques can produce near-net-shape parts and components with unique properties, and without the distortions caused by conventional normalizing and tempering heat-treatments. When combined with sophisticated 3-dimensional computer control to build complex solid metallic shapes, one has the capability of using DF for rapid prototyping. Spray forming using a circular converging/diverging atomizer is a DF process being developed at the Idaho National Engineering and Environmental Laboratory (INEEL) for rapid manufacturing of tool and die steels like H-13. Laser Engineered Net Shaping (LENS{trademark}) is a DF process being developed at Sandia National laboratory (SNL). LENS involves laser-processing fine powder metal sprays into complex, fully-dense 3-dimensional shapes with fine-detail control that would allow rapid prototyping of tools or dies. One logical combination of the two processes is to combine spray forming to replicate most of the die surface and backing, and then t o build other die-surface fine-features with LENS. Premium H-13 steel was used because it belongs to the widely used group of hot-work steels that have good resistance to heat, pressure and abrasion for metal-forging and aluminum die-casting applications. The microstructure and residual stresses that exist across the interface ofmore » a composite metal produced by these two DF methods are critical parameters in producing crack-free components with functional properties. The purpose of this work is to combine unique neutron-diffraction facilities at the Oak Ridge National Laboratory (ORNL) for measuring bulk residual stresses with these two different DF processes to characterize LENS deposits of H-13 steel made on a spray-formed base of that same steel.« less

The heat transfer occurring during laser-based additive manufacturing (LBAM) processes can impact part quality and post-manufactured thermo-mechanical properties – including microstructure and hardness. Effectively managing the heat loss of the manufactured part to the substrate (conduction) and environment (convection) is of great importance. This study experimentally investigates the use of Laser Engineered Net Shaping (LENS) for the additive manufacture of cylindrically-shaped Ti-6Al-4V parts. Using an OPTOMEC LENS ® 750 system, the effect of substrate thickness on post-LENS microhardness and porosity was experimentally investigated. The resultant, transient temperature distribution near the substrate/part intersection was measured using an array of substrate-embedded, type-C (tungsten-rhenium) thermocouples. The effect of the substrate on the substrate/part temperature response was investigated by varying the substrate thickness. The density of the LENS-manufactured part was found to be consistent by ± 0.04 g/cc in relation to each substrate thickness; however, these densities were less than the average density for wrought Ti-6Al-4V suggesting that the parts were somewhat porous for the selected LENS operating parameters. The average Vickers hardness along the crosssection of the part increased with substrate thickness. Compared to the average 349HV for Ti-6Al-4V, the hardness values were 343 HV for the 0.635 cm plate, 359 HV for the 1.27 cm plate, and 368 HV for the 2.54 cm plate. The maximum temperature experienced at the part intersection decreased as plate thickness increased. Heating rate calculated at the outer radius of the part appeared to cause the radial hardness of the first deposited layer to follow a similar curve when built upon the 1.27 cm and 2.54 cm plates.

The mechanical properties and corrosion resistance of 316 L stainless steel fabricated using the Laser Engineered Net Shaping (LENS) technique have been studied. The crack-free, full density samples made using SS316L alloy powder and the LENS technique are characterized by an unusual distinct dual-phase microstructure. STEM analysis revealed a significant increase of Cr and Mo content and a decrease of Ni in the grain boundaries. Based on the Cr and Ni content (austenite stabilizing elements), the Schaeffler diagram and the EBSD results, the existence of intercellular delta ferrite on subgrain boundaries and austenite in the fine-grains are observed. The XRD patterns, in addition to the FCC austenite phase, revealed the second BCC ferrite phase. Moreover, the sigma (FeCr) phases are present in the analyzed 316 L stainless steel. The occurrence of ferrite, which does not occur in regular stainless steel fabricated using conventional metallurgical methods, improves the mechanical and corrosion properties of the LENS-fabricated sample made using 316 L stainless steel powder. The obtained results prove that the microstructure of the SS316L fabricated using LENS is heterogeneous; its impact on the mechanical properties is visible. The analyzed samples are characterized by anisotropic mechanical properties that are favorable. For both the perpendicular and parallel directions of tensile tests, samples had a ductile fracture with many dimples inside of the larger dimples. The corrosion potential of SS316L LENS and classically manufactured steel is similar. The SS316L fabricated using LENS is characterized by a relatively low value of corrosion current density, which translates into much smaller corrosion rates. (C) 2016 Elsevier B.V. All rights reserved.

This paper demonstrates a fiber-sensor fused additive manufacturing process. Distributed fiber optical sensors were metalized through electroplating process and embedded in metal parts using a laser engineered net shaping process. Temperature and strain profiles were monitored in real-time with 5 mm spatial resolution.