Reduction of hot cracking by magnetofluiddynamic modification of the laser-induced melt pool convection during powder-based generative laser cladding

点击翻译按钮获取中文摘要

The occurrence of hot cracking is a significant problem during welding processing of highly heat resistant nickel base superalloys. Hot cracking is most often associated with liquid films that are present along grain boundaries in the fusion zone and the partially melted zone and can only be suppressed to a very limited extent. Latter is the case despite remarkable studies and analyses of the phenomenon. Notable measures are material improvements and thermomechanical treatment which can only be applied with particular arrangements. In the present proposal a new approach is presented which suppresses the cause of hot cracking by using a non-contact method to influence the solidification process. It is based on the laser-induced modification of the melt pool convection (Marangoni convection) using customized magnetic fields. In contrast to an energy input via electron beam or electric arc the laser beam is not interacting with the applied magnetic field. This limits the influence on the flowing melt pool. This limitation is a unique feature and offers the potential for surface applications that are independent from the geometry of the substrate. Besides the substantial theoretical analysis, first experimental results are presented. Latter consolidate the initial working hypothesis. Consequently, an extensive experimental research program will be addressed. This includes in particular the interaction of the melt pool with temporal and/or spatial varying or constant magnetic fields as well as the variation of the melt pool through the systematic adjustment of laser power, focal distance and/or the time of interaction. Identifying the interaction with the melt pool convection requires the present collaboration with considerable expertise and knowledge in laser material processing, fluid dynamics as well as materials engineering and characterization.