Although metal 3D printing (also known as additive manufacturing) is a fairly new technology, its history is deeply rooted in the field of metallurgy and materials science. Researchers such as Carnegie Mellon University’s (CMU) Anthony Rollett recognize materials-science research as an integral component in the transition of 3D printing into a widespread manufacturing process. The research area is necessary in order for manufacturers to make stronger, more-reliable 3D-printed metal parts.

“The 3D-printing process is a high-speed welding process at its heart,” explained Rollett, professor of materials science and engineering. “Similar to welding, we can optimize the materials against the additive-manufacturing (AM) process so that we can produce parts with the maximum strength, best possible fatigue resistance and greatest corrosion resistance.” 

The NextManufacturing Center, which Rollett directs with CMU Mechanical Engineering Professor Jack Beuth, is working to propel the AM field forward in the next five years by optimizing AM materials and the printing process. The center is developing an entirely new approach to metals AM – merging data from all parts of the process to create a fully integrated understanding of the technology.

In the October edition of 3D Printing Report, we explored challenges related to the AM process and how current research will enable advances in this area over the next five years. Now, in part 2, we’ll dive into what is being done to overcome the challenges related to AM materials. 

Metal Powders

Currently, most commercial 3D-metal printers can only print with a few types of metal powders. These powders are made up of very specific particle sizes and can only be purchased from the companies that produce 3D-printing machines. The machine manufacturers require users to buy metal powder from them or risk losing the warranty of their printers. Because of the specialty nature of these metal powders, they are expensive to produce and drive up the cost of the final printed part. 

Companies that hope to use AM to produce a large number of parts find the limitations on metal powders to be particularly challenging because of the cost it can add. Cost is often one of the most defining measures in a company’s decision to adopt AM technology. 

“The question for companies becomes, ‘If we have a metal powder that is a different particle size than we’re supposed to use, can we successfully print a fully dense part?’” Rollett explained. “Our answer is ‘Yes, you actually can.’”

The NextManufacturing Center, in collaboration with North Carolina State University, has discovered how to 3D print with different metal powders, many that would normally be discarded because of their larger particle size and course texture. The center estimates that all 3D-printing machine users will be able to adopt these practices over the next five years in order to use a wide variety of metal powders in 3D-printing machines. This means that manufacturers will be able to purchase less-expensive metal powders from a wider range of distributors. 

Controlling Porosity

Materials science also plays a key role in improving the internal structure of AM metal parts. The biggest challenge is porosity, or tiny defects in the printed part, which makes the part susceptible to breakage (fatigue or fatigue failure) when it is exposed to repeated stress. Currently, some level of porosity is unavoidable if a manufacturer were to use a 3D metal printer’s suggested process parameters. 

NextManufacturing researchers, however, have the knowledge required to control the porosity down to safe levels in AM metal parts. Rollett and his group use advanced characterization techniques to study metal printing powders and better understand how and why porosity forms in printed parts. Using this fundamental scientific approach, the group can determine how to eliminate the tiny defects. Using advanced characterization to visualize porosity with such high precision is a breakthrough capability in additive research. 

Rollett and Beuth say that these results will be transferred to industry in the next five years, and users will be able to both eliminate and manipulate porosity in printed parts.

Looking Forward 10 Years: Developing New Alloys and Using Machine Learning in 3D Printing

The NextManufacturing Center is not only focused on identifying and solving AM challenges over the next five years, it is already looking ahead to what industry will need in the next decade. 

One of these key areas is the development of new AM alloys. 

“The metal powders that manufacturers are currently using for 3D printing were actually designed and optimized for conventional manufacturing processes,” Rollett explained. “There is a growing need for materials that are instead optimized for additive-manufacturing processes and their high cooling rates.” 

Rollett and his colleagues are working on several projects in this space. Within 10 years, users will have a wider range of materials to choose from when printing. 

The second key area is the use of machine learning in additive manufacturing. By combining materials-science research and computer-science techniques, the NextManufacturing Center (in a project led by Elizabeth Holm, professor of materials science and engineering at Carnegie Mellon) is compiling a database of experimental and simulated metal-powder micrographs in order to better understand what types of raw materials are best suited for 3D-printing processes. Machine learning can potentially be used for better, more standard part qualification.

“3D printing is one of the best things to happen to the field of metallurgy in the past 100 years,” Rollett said. “The technology is challenging our engineers to think in completely new ways, and it is inspiring us to create interesting new collaborations across disciplines.”