New technological developments in laser cladding

A novel powder feeding system designed for the requirements of laser surface treatment is presented. lt permits the feeding of metallic and ceramic powders with grain sizes bigger than 20 mym, and is characterized by feed rates between 1 and 150 g/min. The tolerances of the feeding rate are less then 3 percent. The on-line measurement of the powder mass flow rate enables the fast and precise setting, long time constancy and variable control of the feed rate during the whole treatment process to be achieved. Because of its compact design and low weight, the entire powder feeding device can easily be attached to a laser working head. For cladding with wide focal areas broad cladding tracs of good quality and low dilution can be produced using powder nozzles with large diameters. In addition, the adapted configuration of laser beam and powder supply results in high coupling rates and a high cladding efficiency. Furthermore, the experimental results show that by adaptive regulation of the laser output power the track shape and composition can be controlled in a wide range. This is done by measuring the melt pool temperature via pyrometer and regulating the laser power according to the setting of a PID-controller. Especially for overlapping tracks and for cladding of workpieces of small volume, the presented method of melt bath diagnostics is a useful instrument to ensure constant cladding quality