Curved Small Tungsten Macro-Brush Test Mock-Up Fabrication Using Vacuum Brazing for Divertor Target Elements

The aim of the work is to develop the fabrication technology of a small curved tungsten (W) macro-brush–type geometry using a vacuum brazing technique. Taking the design concept of the ITER divertor dome, the present mock-up has scaled down more than ten times in size. A feasibility study of the curved brazing was done, and design and fabrication of the special fixture for the curved profile brazing were carried out. The vacuum brazing technique was used to develop the joining of tungsten tiles in the curved profile of a CuCrZr block (heat sink) using silver-free brazing alloy (NiCuMn-37) with a specially designed custom-made fixture (Type 304 stainless steel). Nondestructive testing, particularly the ultrasonic immersion technique, was incorporated to inspect the quality of the brazed joint in the mock-up. The hardness value (HV) measured on the copper alloy was found to degrade from 143 to 46 HV (before and after brazing). The results of the experimental activity and methodology adopted to fabricate the small-sized trial W mock-up are presented and discussed in the paper.