Laser deposition welding's powder gas stream can now be analysed by illuminating it with another laser and capturing images with a camera for analysis.
Laser material deposition is now used for the repair and manufacture of metal parts. Material is deposited layer by layer using a nozzle, injecting a powder that is melted by the laser. The delivery of powder to the molten layers is crucial because it has a major influence on powder consumption.
Scientists at the Fraunhofer Institute for Laser Technology have succeeded in performing qualitative and quantitative characterisation of the powder gas stream using a laser, camera system.
The camera has a high frame rate that allows users to determine the number and position of individual powder particles at a defined point in time. The lateral laser beam moves down the powder gas stream layer by layer, capturing in a few seconds the data for each layer. The system then calculates the particle density distribution for each layer. The scientists expect that this new measuring technique will aid, in particular, engine and power plant manufacturing, tool making and mechanical engineering.
Stefan Mann, the project’s leader, said: '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.’
Until now, the only way of determining the factors spelt out by Mann was to create reference samples of parts made or repaired with laser metal deposition. Correlating these samples with comparative deposited welds revealed the quality of the nozzle.
