Metal additive manufacturing is a rapidly growing and sophisticated industry however the manufacturing processes and equipment for the heat treatment of the needed powdered metals are underdeveloped.  Heat treatment is a key step in the powdered metal production process and is often needed to produce desired material properties.  This heat treatment is difficult for several reasons. First, the small particle-to-particle surface contact area of powered metals causes it to have a relatively low thermal conductivity which inhibits heat transfer and effective and efficient heat treatment. Second, additive manufacturing applications often require several different powdered metal compositions.  Each will typically have different heat treatment manufacturing parameters such as temperature profile and dwell time. Lastly, the tendency of powdered metals to oxidize at elevated temperatures can necessitate that heat treatment occur under a protective gas atmosphere. These difficulties create the need for a new powdered-metal heat-treatment apparatus with a high heating rate, a range of heat treatment parameters, and a controlled environment. A laboratory-scale device has been designed that achieves these objectives.  This apparatus utilizes continuous flow of powder through a quartz tube allowing for a small cross-sectional area of flow, with a high surface area per volume, to be exposed to the heat source. The high surface area per volume allows for a high heating rate to be achieved. This tube resides within a tube furnace but is physically isolated from the furnace. This isolation allows for the use of vibratory feeders to generate powder flow in the tube. This source of motion is ideal since it limits contact with the powder, has limited moving parts, and provides a broad range of feed rates. The adjustability of the vibratory feeders combined with the temperature control on the tube furnace allows for a broad range of heat treatment parameters. Lastly, the apparatus includes a gas handling system and prevents powder oxidation by operating under a vacuum or under an inert gas environment. Testing has confirmed that the apparatus is successful in achieving all objectives. It is capable of achieving a heating rate that is significantly higher than current methods. Powder residence time and temperature can be varied from 10 seconds to several hours and from 200C to 1100C respectively. The environmental control system is capable of producing a medium vacuum (20 Pa) as well as an inert gas environment.  The environmental control system was found to be particularly useful for powders which release gaseous by-products during heat treatment. Under vacuum alone, these by-products can significantly disrupt powder flow however the introduction of a small amount of inert gas counters this effect. The designed and constructed apparatus is a fully functioning research and development tool. It will be used in a research laboratory and will provide consistent results to aid in the further development of high-quality powdered metals. This machine is capable of meeting all of the requirements for a laboratory setting and is versatile enough to be used on many powdered metals that require post processing before being used for additive manufacturing. This method is novel and provides advantages that include faster heat treatment times, the capability of processing a broad range of materials, and a controlled environment.


Powdered Metal Heat Treatment Apparatus Designed for a Laboratory

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

IMECE2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.