420 stainless steel-Cu parts fabricated using 3D Multi-Material Laser Powder Bed Fusion: a new solution for plastic injection moulds

A novel multi-material design concept to be applied in plastic injection moulds is proposed combining the mechanical resistance of the 420 stainless steel alloy and the high thermal conductivity of copper, in a single component, fabricated in just one event by means of homemade 3D Multi-Material Laser Powder Bed Fusion equipment. The processing strategy and the interface region between both materials are analysed and discussed both from a metallurgical and mechanical point of view. The results show a good metallurgical bonding between the two materials, with a diffusion zone of about 10 mu m, capable of providing mechanical interlocking, i.e. entrapment of one material in the other, creating a physical link between them. Both materials have low porosity and the pores detected present a sub-micrometre size distribution. A few pores and cracks on both the top and cross-section surfaces were detected with some tens of micrometres in size, at the interface zone. The hardness of the 420 stainless steel and copper varied from 482 to 532 HV and 99 and 116 HV, respectively.