Quality Related Effects of the Preheating Temperature on Laser Melted High Carbon Content Steels

Additive manufacturing technology selective laser melting (SLM) is an emergent technology allowing generation of complex metal parts layer by layer. During the past years the range of available and processable materials for SLM has been widely extended. However, there is a still a lack of SLM processable high carbon content steels. In the fields of machine elements, especially in advanced cutting tools a large potential of laser melting is identified regarding function integration, topology optimisation and implementation of bionic concepts. In these fields of application high carbon content steels are frequently used. The M2 High Speed Steel (HSS) is a high carbon content steel that belongs to the group of tool steels. As other high carbon content steels, M2 HSS tends to a high susceptibility to cracking. Therefore, the strongly pronounced temperature gradients occurring during the laser melting process lead to part deformation and crack formation. Heating of the SLM baseplate represents a promising approach to reduce temperature gradients and internal stresses. In the present study the quality related effects of reduced temperature gradients on SLM parts were evaluated using a baseplate heating system. Optimized process parameters allowed a stable processing of M2 HSS leading to a relative part density of 99%. Residual stresses decreased with increasing baseplate temperature by trend.