3D multi-material 420 stainless steel-copper parts for improved thermal conductivity of plastic injection moulds: a step forward in laser powder bed fusion
摘要
The demand for manufacturing multi-functional parts is increasing by the requirement for versatile parts that can adapt to different functions, all in the same component. 3D Multi-Material Laser Powder Bed Fusion is an advanced manufacturing tool to enable the fabrication of complex multi-functional parts. In the present study, this technology was exploited to print multi-material part of high-strength 420 stainless steel alloy with copper heat flow channels, all printed at once. This solution aims to enhance the capacity of plastic injection moulds to extract heat with minimum impact in the mechanical strength. The processing strategy, the interface region between both materials, and the stresses associated with thermal cycles of the plastic injection moulding process are analysed and discussed from a metallurgical, mechanical, and thermal point of view. The 420 stainless steel-copper interface was found to be well-defined and sharp, with no significant diffusion being observed both in the as-built sample and samples subjected to continuous thermal cycles. The incorporation of 4 vol.% copper led to a ~ 22% reduction in the electrical resistivity of the multi-material samples (~ 31 µΩ cm) compared to the mono-material specimens resulting in a thermal conductivity of the 420 stainless steel-copper sample (23.37 W/m K) significantly higher than that of the 420 stainless steel samples (15.30 W/m K). No cracks associated with the continuous heating and cooling steps inherent to the mould were detected, but changes in the microstructure and consequently in the hardness values were observed.