Ni/Me (Me = Al or Ti) reactive multilayer thin films with total thickness close to 2 -3 µm and modulation periods (bilayer thickness) between 12 and 60 nm have been successfully used to enhance the diffusion bonding process – reaction-assisted diffusion bonding (RADB) [1]. The Ni/Me reactive multilayer thin films with nanometric periods are directly deposited onto the base materials by magnetron sputtering from two targets. The power applied to each target is selected in order to obtain near equiatomic average chemical composition, while the period is adjusted by varying the substrates’ rotation speed.

Similar and dissimilar metallic joints have been obtained by RADB using less demanding conditions, namely lower temperature, time, or pressure. For instance, using Ni/Ti nanomultilayers  sound joints were achieved between NiTi and Ti-6Al-4V at 600 °C during 30 min, under 10 MPa [2]. This approach was also applied to ceramic/metal joining, and for this purpose Ti-6Al-4V and Al2O3 base materials were coated with reactive multilayer thin films [3]. Using Ni/Ti multilayer thin films with nanometric periods, Ti-6Al-4V and Al2O3 were joined at 800 °C during 60 min, under 5 MPa. The use of the reactive multilayers proves to be effective, since without interlayer sound joints between these base materials could not be achieved under the selected conditions.

The use of Ni/Me reactive multilayers with nanometric period presents a clear advantage in relation to the process without interlayer material. The nanomultilayers improve the contact between the joining surfaces and enhance the joining process due to the improved reactivity and diffusivity resulting from their exothermic and nanometric character.

Recently, the RADB joining strategy is being considered for the mold industry. Due to the large dimensions, it is not feasible to produce the whole mold by additive manufacturing, e.g. by laser powder bed fusion (LPBF), which poses the challenge of efficiently joining the molding surface/inserts to the base of the mold.