Production of a multi-functional 420 stainless steel-copper surface by laser texturing and hot pressing: a new solution for plastic injection moulds

The aim of this work was the development, production and characterisation of a multi-functional surface, consisting of a 420 stainless steel surface textured by laser and subsequently filled with pure copper by hot pressing, for plastic injection moulds. The influence of pure copper on the physical, chemical, surface, mechanical and thermal properties was analysed. The textured pattern consisted of unidirectional lines with a machined volume of approximately 12%. The steel and pure copper interface after sintering were well defined and sharp, and no significant diffusion was observed in the multi-material part produced. The pure copper zones exhibited grains of a quite heterogeneous size (lower than 50 µm) with twins and micropores at the grain boundaries, while the 420 stainless steel consisted of an iron-rich matrix (grains lower than 10 µm) and Cr₂₃C₆. The hardness values of the 420 stainless steel and copper measured were 385 HV and 84 HV, respectively, and the thermal conductivity of the multi-material solution was ≅ 4 times higher than the 420 stainless steel (62.54 and 15.72 W/m K, respectively).