This work is framed in the joining technologies for fusion reactor applications, more specifically in ITER tungsten-to-steel joints. The main problem for W/steel joints is the mismatch between the coefficients of thermal expansion of tungsten and steel that after joining process causes residual stresses at the interface, reducing the strength of the whole joint. Moreover, the deeper diffusion of the metallic filler (in case of brazing) leads to a softening in the seam area and consequently has a detrimental effect on mechanical properties. Finally, the direct contact between copper and steel causes the formation of a reaction layer constituted of brittle compounds which weaken the whole joint.