Development, thermomechanical analysis, fabrication and testing of a macro-block-divertor specimens

For a divertor element with internal coolant flow reversal Carbon Fibre reinforced Carbon brazed on a Cu-base or refractory metal cooling tube was selected. In order to choose the optimum geometry and material combination, two criteria in the thermomechanical FEM analysis were used: the surface temperature under a thermal load of 10 MW/m2 and the residual stress in the CFC-material after brazing. Based on the results of the FEM calculations test specimens in macro-block-geometry made of a 2D-CFC material brazed to an OFCu tube were manufactured using a CuTi braze. In order to study the influence of the brazing parameters, the size of the braze gap and the formation of the CuTi-phase were varied. To evaluate the thermal behaviour, heat load experiments up to 10 MW/m2 for pulse durations of 5 s, 10 s and 15 s were applied in an electron beam facility. Before and after brazing all Cu-CFC interfaces were non-destructively tested using a high resolution ultrasonic inspection system. A very good agreement between thermography, ultrasonic inspection and metallography of the braze joints was observed. Due to these results new larger test specimens were produced using a smaller brazing gap and the vacuum plasma deposition of Ti for the formation of the braze. (author)