Powder bed fusion of soft-magnetic iron-based alloys with high silicon content

Powder bed fusion of metal with laser beam (PBF-LB) of application-ready parts of iron-silicon alloys with a high silicon content is both promising and challenging. Although a higher silicon content significantly improves the soft-magnetic behaviour, it also promotes brittleness and thus, makes these alloys barely suitable for the pro-duction of parts with a height larger than a few millimetres. To overcome these challenges, the potential of a build-chamber preheating system implemented in a standard PBF-LB machine is investigated in terms of the defect-and crack-free manufacturing of large-scale samples and components of brittle iron-silicon alloys. In addition, the current study analyses the influence of the silicon content on the soft-magnetic and mechanical behaviour of additively processed iron-silicon alloys. For this purpose, four alloys with a silicon content between 2.4 wt.-% and 10.0 wt.-% are processed into samples with different dimensions. Subsequently, the manufactured samples are heat-treated and the resulting influence of both, the Si-content and the heat treatment on the microstructure as well as the soft-magnetic and mechanical properties are analyzed. As it is shown, defect-and crack-free parts can be manufactured independently of the dimensions. Iron alloyed with 6.7 wt.-% of Si exhibits the best permeability of all investigated alloys, which can be further improved up to 1.5 times by applying a suitable heat treatment. Thus, the results obtained build a basis for powder bed fusion of application-adapted parts with outstanding soft-magnetic properties, which can be barely manufactured using conventional form-ing technologies.