Laser cladding of glass-ceramic sealants for SOFC

One of the recent developments in the joining technology for SOFC is the laser assisted welding. Nowadays, the sealing of the cell is carried out by heating the entire stack in a furnace and through a sintering-crystallization process of the glass powder at the operation temperature (700-900 °C). The laser welding implies temperatures above 1200 °C but a high reduction in the sealing time (only a few minutes). In this work, the laser cladding of glass-ceramic sealants on Crofer22APU has been studied, employing a glass composition that previously showed appropriate properties for sealing SOFC. To evaluate the suitability of this technique, the quality of the joint between the steel Crofer22APU and the glass-ceramic has been studied directly after laser cladding, thermal treatment and thermal cycling. The crystallization kinetics, crystalline phases and 11B-NMR were studied. The residual stresses in the steel after laser welding have also been evaluated by X-ray diffraction using Synchrotron radiation.