Which additive manufacturing process is best suited for metal processing?

Dr. Horst Hill is Head of Special Materials at Deutsche Edelstahlwerke (DEW) in Krefeld. © DEW

Dr. Horst Hill: A general answer is not possible here. On the one hand, the various processes offer different advantages and disadvantages; on the other hand, the choice of process depends largely on the component in question and the application. Last but not least, it also depends on which materials are available and can be processed. Additive manufacturing using the powder bed process is certainly one of the most widespread, as it enables very complex components and has therefore already opened up many fields of application.

How does powder metallurgical processing work?

First, the individual raw materials are charged into a furnace and melted down - you can think of this process as cooking according to a recipe. The molten metal is then fed through a nozzle system and atomized under high pressure. The molten droplets solidify and this is how the metal powder is obtained.

Can all metals be processed using powder metallurgy?

Theoretically, yes. The "trick" is that the melt has to be guided through the nozzle system properly. We are talking here about "atomizability" - this depends on the one hand on parameters such as pressure and temperature. On the other hand, it also largely depends on the chemical composition. Therefore, many things are possible, but there are always technical limitations.

Deutsche Edelstahlwerke offers various metals and metal alloys in both solid and powder form. Assuming a component is milled once and additively manufactured once from the same metal, to what extent do the finished components differ in terms of stability and robustness?

Additively manufactured components, for example using a powder bed, are generally characterized by a significantly finer-grained microstructure. In accordance with the Hall-Patch relationship, higher strength values with higher toughness are possible at the same time. On the other hand, conventionally produced materials are often superior in terms of fatigue strength, as one or two pores cannot be avoided, for example, which in turn is reflected in the properties.

However, if the processing characteristics of both mass production and additive manufacturing are taken into account in material development and alloy design, very comparable property profiles are at least possible. One example of this is the bainitic material Bainidur developed by Deutsche Edelstahlwerke, which is available as a forged product and metal powder. This enables our customers to use rapid prototyping with metal powder in the development stage. The components produced in this way can be examined and tested - even the heat treatment can be tested. Our forged products are then used in series production without the customer having to develop a completely new product.

What trends in materials and additive manufacturing can the industry expect in the coming years?

We focus on developing new materials that are optimized to meet the requirements and general conditions of additive manufacturing. One example of this is our newly developed and patent-pending Printdur HSA. This is a high-strength austenitic material that makes targeted use of the rapid cooling speeds in the powder bed process to develop the microstructure. In addition, this material does not contain nickel, which is very important from an occupational safety perspective.