A team of engineers has been refining laser powder buildup welding over decades to allow more materials to be applied in additive manufacturing.

Engineers at the Fraunhofer Institute for Material and Beam Technology (Fraunhofer IWS; Dresden, Germany) have refined laser powder buildup welding over decades to allow more materials to be applied in additive manufacturing. In this procedure, a system feeds various filler powders into a process zone where a laser melts the powder and deposits it on a workpiece surface. As a result, the desired part is generated in a layer by layer process.

Pictures courtesy Fraunhofer IWS Dresden. By means of laser powder build-up welding, components made of different materials can be integrally manufactured. Thus, specific materials can be placed exactly where their properties are required. This offers, for example, the prospect of lighter, better and cost-reduced blades for gas turbines

“One of the advantages of this additive procedure is that we can adapt the process very flexibly to the requirements of high-performance materials,” explains Michael Müller, Fraunhofer IWS project administrator. In this way, it is also possible, for example, to print nickel-based alloys that are difficult to weld and process using traditional methods. However, this only works if the temperature, powders, feed rate, and other parameters are correct.

Within the framework of Fraunhofer’s futureAM – Next Generation Additive Manufacturing project, Fraunhofer IWS engineers are recording numerous sensor data with very high sampling rates for this purpose. However, this generates large amounts of data (big data) that are difficult for people to understand.

AI learns to decide
Nevertheless, Fraunhofer experts use artificial intelligence (AI) and machine learning, which are also being studied in a working group led by Prof. Karol Kozak, head of image processing and data management at Fraunhofer IWS, to find hidden connections in these signal floods. For example, special analysis algorithms link the measured sensor values with the institute’s powder database and evaluate further process parameters and gradually the machines learn to make their own decisions. For instance, they can determine for themselves whether a slight rise in temperature in the welding process can be tolerated or whether they have to take immediate countermeasures before the entire component ends up as waste.

Better aircraft engines in sight
Aircraft engines, for example, could work more efficiently and at higher temperatures if most materials were not already failing at temperatures of around 1 200°C. Admittedly, there are materials that can withstand such high temperatures, but they are very cost-intensive and difficult to process using traditional methods. Additive manufacturing is intended to solve this dilemma and could help to achieve a more cost-effective design.

Fraunhofer IWS Dresden has developed a process and material database which stores all details of the manufactured components. This database allows complex conclusions between the welding result and already obtained data

“Using laser powder buildup welding, we can feed different powders into the process zone simultaneously or successively with precisely adjustable feed rates,” Müller explains. “Designing an entire component out of a singular material is not very effective since the component is not exposed to the same heat at all points.”

In the futureAM project, Fraunhofer IWS and five other Fraunhofer Institutes are pooling this technology and further expertise to push additive manufacturing to a new level. By summer 2020, they want to integrate all their expertise into the additive manufacturing process chain and demonstrate it on realistic components.

For more information, please visit iws.fraunhofer.de