Optimization of SLM productivity by aligning 17-4PH material properties on part requirements

The purpose of this study is the development of a global SLM-manufacturing optimization strategy taking into account material porosity and SLM process productivity. Selective laser melting (SLM) is a master forming process generating not only a near net shape geometry, but also the material with its properties. Research focuses primarily on optimal processing parameters for maximised material properties. However, the process allows also designing the material structure by internal porosity, affecting global material properties and the process productivity.

The study investigates the influence of the main SLM process parameters on material porosity and consequently on the static mechanical properties of hardened SS17-4PH material. Furthermore, a model for the SLM scanning productivity is developed based on the SLM processing parameters.

The results show a clear correlation between porosity level and mechanical properties. Thereby, the mechanical strength and material modulus can be varied in a wide range. The degree of internal material porosity can be correlated to the energy input defined by a set of SLM processing parameters, such as Laser power, powder layer thickness and scan speed, allowing pre-definition of a specific degree of porosity.

Aligning of the SLM processing parameters to the technical material requirements of the parts to be produced, e.g. maximal stresses in service, required E-modulus or lightweight aspects, enlarges the general design space significantly. In combination with the presented model for the scanning productivity, it is further possible to optimize the SLM build rate.