Sandia National Laboratories is developing a technology called Laser Engineered Net ShapingTM (LENSTM). This process allows complex 3-dimensional solid metallic objects to be directly fabricated from a CAD solid model. Experiments performed demonstrate that complex alloys such as Inconelm 625 and ANSI stainless steel alloy 3 16 can be used in the LENSTM process to produce solid metallic shapes. In fact, the fabricated structures exhibit grain growth across the deposition layer boundaries. Mechanical testing data of deposited 3 16 stainless steel material indicates that the deposited material strength and elongation are greater than that reported for annealed 3 16 stainless steel. Electron microprobe analysis of the deposited InconelTM 625 material shows no compositional degradation of the 625 alloy and that 100% dense structures can be obtained using this technique. High speed imaging used to acquire process data during experimentation shows that the powder particle size range can significantly affect the stability, and subsequently, the performance of the powder deposition process. Finally, dimensional studies suggest that dimensional accuracy to kO.002” ( in the horizontal direction) can be maintained.

The primary purpose of this LDRD project was to characterize the laser deposition process and determine the feasibility of fabricating complex near-net shapes directly from a CAD solid model. Process characterization provided direction in developing a system to fabricate complex shapes directly from a CAD solid model. Our goal for this LDRD was to develop a system that is robust and provides a significant advancement to existing technologies (e.g., polymeric-based rapid prototyping, laser welding). Development of the process will allow design engineers to produce functional models of their designs directly from CAD files. The turnaround time for complex geometrical shaped parts will be hours instead of days and days instead of months. With reduced turnaround time, more time can be spent on the product-design phase to ensure that the best component design is achieved. Maturation of this technology will revolutionize the way the world produces structural components.

Direct metal deposition technologies produce complex, near net shape components from CAD solid models. Most of these techniques fabricate a component by melting powder in a laser weld pool, rastering this weld bead to form a layer, and additively constructing subsequent layers. This talk describes a new direct metal deposition process, known as WireFeed, whereby a small diameter wire is used instead of powder as the feed material to fabricate components. Currently, parts are being fabricated from stainless steel. Microscopy studies show the WireFeed parts to be fully dense with fine microstructural features. Initial mechanical tests show stainless steel parts to have good strength values with retained ductility.

The direct additive manufacturing of metallic components can present several process challenges. At present, there are several techniques for the accomplishment of this goal l ,2, each withits own set ofstrong points and limitations. At Sandia,LaserEngineered Net Shaping, or LENS, is a process.which has been. developed for the direct additive·. manufacturing i of fully dense three dimensional parts. In LENS, a Nd-YAGlaser is focused onto a metallic substrate or onto previously deposited material. Thelaser melts the metal and a small pool of metalforms. Powder is injected into the pool and a bead forms. Byrastering an x-y table to which the partis affixed in a controlled fashion, the bead is pulled and afully dense metal partis formed. As currently configured, LENS isa 2VzD process.

The Laser Engineered Net Shaping (LENS(TM)) process, currently under development, has demonstrated the capability to produce near-net shape, fully dense metallic parts with reasonably complex geometrical features directly from a CAD solid model. Results to date show that excellent mechanical properties can be achieved in alloys such as 316 stainless steel and Inconel 625. In fact, due to the highly localized nature of the laser heating, a fine grain structure will occur resulting in a significant increase in yield strength at no expense of ductility. The current approach lends itself to produce components with a dimensional accuracy of +/-.002 inches in the deposition plane and +/-.0.015 inches in the growth direction. These results suggest that this process will provide a viable means for direct fabrication of metallic hardware directly from the CAD solid model.

Rapid prototyping techniques have revolutionized the approach to fabricating geometrically complex hardware from a CAD solid model. These techniques allow component designers to directly fabricate conceptual models in plastics and polymer coated metals; however, each of these techniques requires additional post processing to allow the fabrication of functional metallic hardware. This limitation has provided the impetus for further development of freeform fabrication techniques which enable fabrication of functional metallic hardware directly from the CAD solid model. The Laser Engineered Net Shaping (LENS(TM)) process holds promise in satisfying this need. This newly emerging technology possesses the capability to fabricate fully dense components with good dimensional accuracy and with unique material properties. Relatively complex geometrical shapes have been fabricated using this technology. In continuing to develop the LENS(TM) process, further advancements are required. The functional dependence of the component surface finish and microstructural characteristics on process parameters including powder size and size distribution are being characterized. A set of statistically designed experiments is being used to sort through the various process parameters and identify significant process variables for improving surface finish and achieving optimum material microstructural properties.

Direct metal deposition technologies produce complex, near net shape components from CAD solid models. Most of these techniques fabricate a component by melting powder in a laser weld pool, rastering this weld bead to form a layer, and additively constructing subsequent layers. Powder feed material in these processes results in near net shape, high strength components, with the ability to blend materials for novel properties. This talk will describe a new direct metal deposition process, known as 3DWire, whereby a small diameter wire is used instead of powder as the feed material to fabricate components. This allows for faster deposition rates, smoother surface finishes, and easy material handling. Currently, parts are being fabricated from 308L stainless steel and Aermet{reg_sign} 100. Microscopy studies show the 3DWire parts to be fully dense with fine microstructural features. Initial mechanical tests show stainless steel parts to have good strength values ({sigma}{sub y} = 58 ksi, {sigma}{sub ult} = 95 ksi, 87 HRB) with retained ductility (65%).

Rapid prototyping (RP) has revolutionized the approach to fabricating geometrically complex hardware from a CAD solid model. The various RP techniques allow component designers to directly fabricate conceptual models in plastics and polymer coated metals; however, each of the techniques requires additional processes, e.g. investment casting, to allow the fabrication of functional metallic hardware. This limitation has provided the impetus for further development of solid freeform fabrication technologies which enable fabrication of functional metallic hardware directly from the CAD solid model. The Laser Engineered Net Shaping (LENS{trademark}) process holds promise in satisfying this need. This newly emerging technology possesses the capability to fabricate fully dense components with good dimensional accuracy and with unique materials properties. Relatively complex geometrical shapes have been fabricated using this technology. In continuing to develop the LENS{trademark} process, further advancements are required. The functional dependence of the component surface finish and microstructural characteristics on process parameters including power size and size distribution are being evaluated. A set of statistically designed experiments is being used to sort through the various process parameters and identify significant process variables for improving surface finish and achieving optimum material microstructural properties.

Sandia National Laboratories is developing a technology called Laser Engineered Net Shaping{trademark} (LENS{trademark}). This process allows complex 3-dimensional solid metallic objects to be directly fabricated for a CAD solid model. Experiments performed demonstrate that complex alloys such as Inconel{trademark} 625 and ANSI stainless steel alloy 316 can be used in the LENS{trademark} process to produce solid metallic-shapes. In fact, the fabricated structures exhibit grain growth across the deposition layer boundaries. Mechanical testing data of deposited 316 stainless steel material indicates that the deposited material strength and elongation are greater than that reported for annealed 316 stainless steel. Electron microprobe analysis of the deposited Inconel{trademark} 625 material shows no compositional degradation of the 625 alloy and that 100% dense structures can be obtained using this technique. High speed imaging used to acquire process data during experimentation shows that the powder particle size range can significantly affect the stability, and subsequently, the performance of the powder deposition process. Finally, dimensional studies suggest that dimensional accuracy to {+-} 0.002 inches (in the horizontal direction) can be maintained.

Solid free form fabrication is a fast growing automated manufacturing technology that has reduced the time between initial concept and fabrication. Starting with CAD renditions of new components, techniques such as stereolithography and selective laser sintering are being used to fabricate highly accurate complex 3-D objects using polymers. Together with investment casting, sacrificial polymeric objects are used to minimize cost and time to fabricate tooling used to make complex metal casting. This paper describes recent developments in LENS{trademark} (Laser Engineered Net Shaping) to fabricate the metal components {ital directly} from CAD solid models and thus further reduce the lead time. Like stereolithography or selective sintering, LENS builds metal parts line by line and layer by layer. Metal particles are injected into a laser beam where they are melted and deposited onto a substrate as a miniature weld pool. The trace of the laser beam on the substrate is driven by the definition of CAD models until the desired net-shaped densified metal component is produced.

A series of experiments have been performed to characterize the laser spray powder deposition tea-one (HAZ) in the process. Goal of these experiments was to minimize the heat affected base substrate while obtaining a maximum build-up rate of the deposited material. Response surface models have been developed to achieve this goal. These models indicate that laser irradiance and component travel speed are both important factors to be considered in optimization of this process. These models suggest that a minimum HAZ can be obtained with a maximum material build-up height by maintaining with a slow travel speed. Although these models are useful in identifying significant factor and process trends, further refinement is required for practical use in industrial applications. Weighting of the response variables used in generating the models is being considered to improve the model robustness. High speed imaging of the deposition process suggests that the powder particle size and/or size distribution affects the stability of this process.