DED Metal 3D Printing Study Reduces Errors in Functionally Graded Materials –


FGMs are used to create properties of parts that change throughout their geometries by mixing different materials, changing their crystallization, or changing their layout. This means that in a single printed object you can create a rigid, soft, hard and flexible iPhone case in different places. We don’t really know at this time what FGMs can do for us or to what extent they will be used in 3D printing in the future. However, we can be sure that it will lead to new apps, if all issues are resolved.

One of these flaws is the lack of process control in general and errors in components. The Korean team has now sought to control the mixing of different materials at different ratios to see where errors occur. What’s really cool is that they did this for Directed Energy Deposition (DED) which got much less attention than Powder Bed Fusion (PBF) in research circles. In this case, they looked at the interface layers between different materials, 316(L) stainless steel and Inconel 718. Between the layers, cracks and flaws can appear and ideally the right mix of materials relative to each other can reduce this.

Inconel 718 has an excellent Properties, but it’s expensive. By mixing it with OHS 316L to create a high-performance FGM, we not only improved his technical and commercial advantages, but his economic feasibility as well,” said Professor Do-Sik Shim.

The team used an Optomec LENS system for their experiment, building a series of parts and playing with gradients, as well as laser power and feed rate. They created components in which the steel was printed on the Inconel, with graded variants mixed at 10% and 25%. In the non-gradient sample, cracks formed between the two materials. In contrast, the graded samples “showed cracks only in specific regions due to a ‘columnar to equitaxial transition’ (a transition in the microstructure of the FGM), precipitation, or inclusion of impurities from titanium, aluminum or chrome. Meanwhile, the 25% graded sample “showed the highest tensile strength and elongation.”

“These findings will lead to improvements in the field, such as reduced costs, extended equipment component lifespans and improved functionality,” Professor Shim said.

Now the team will look at the geometries and how they affect their results. DED is still considered a very crude technology. I half jokingly call it metal Cheez Whiz. Lack of control over temperatures and airflows, as well as rough layers, means the process often requires a lot of machining and cannot build the most complex parts. However, the PBF is limited by the size of the chamber, which makes large one meter long chambers very expensive. During this time, large parts of the binder jetting will deform or collapse under their own weight in a green state. DED is truly our best bet for creating very large structural parts of several meters or more. The type of work done by the Korean team could advance the DED to the point where it becomes a more viable production technology.


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