Novel approach for suppressing of hot cracking via magneto-fluid dynamic modification of the laser-induced marangoni convection
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. The latter is the case despite remarkable studies and analyses of the phenomenon. In this work, a new approach is presented which intends the suppression of hot cracking by using a non-contact method to influence the solidification process. It is based on the idea of a modification of the laser-induced melt pool convection (Marangoni convection) using customized magnetic fields. As a consequence, special system technology is derived on the basis of theoretical considerations while the effectiveness to be expected is estimated on the basis of the information available in the literature. The implemented system technology is described in detail. The focus of this description is on the magnetic flux density distribution or the temporal change, respectively, with respect to the laser-induced melt pool. The presented experimental results provide a comparative view of samples welded with and without the influence of a magnetic field while a significant difference is evident. The outlook of this work describes key data of a test stand specially developed for examining the identified topic in in-depth investigations.