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Laser Deposition Welding Fraunhofer breakthrough boosts control of laser material deposition

Editor: Eric Culp

The institute’s ability to perform 3D characterizations of powder gas streams is said to improve process quality and cut costs.

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Particle density distribution of different layers of a powder gas stream (three beam powder nozzle).
Particle density distribution of different layers of a powder gas stream (three beam powder nozzle).
(Source: Fraunhofer Institute for Laser Technology ILT, Aachen)

Scientists at the Fraunhofer Institute for Laser Technology in Aachen say they can perform qualitative and quantitative characterization of the powder gas stream in laser deposition welding. “For the first time, we have succeeded in developing a measuring procedure that enables us to determine the constancy of the powder mass flow, the symmetry of the powder gas stream, and the position and size of the powder focus,” says Stefan Mann, who is in charge of the project at the institute.

Potential applications of this new measuring technique include all activities in the field of laser deposition welding, in particular engine and power plant manufacturing, tool making and mechanical engineering.

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Laser material deposition has become an established processing technique for the repair and manufacture of metal parts and the functionalization of metal surfaces. A nozzle injects a powdered filler material into the melt generated by the laser beam. This produces a layer metallurgically bonded to the workpiece.

It’s a gas, a powder gas that is

The powder gas feed is an important parameter of the overall process and plays a key role in the results, researchers said. Precise knowledge of the powder gas stream forms a necessary component in maintaining process quality, so delivery of powder to the melt pool via the nozzle serves as a crucial element in this process.

It has a major influence on the consumption of powder material, the effectiveness of the gas shielding system used to prevent oxidation, and the quality of the coating layer. In order to ensure consistently high process stability and quality, the scientists say it is necessary to check the processing results at regular intervals because nozzle wear can lead to deviations that change the diameter and position of the powder focus. Orientation of the powder gas stream to the laser beam is of major importance.

Until now, the only way of determining these changes was to use laser metal deposition to obtain reference samples. Correlating these samples with comparative deposited welds revealed the quality of the nozzle.

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