Influence of post-processing milling conditions on the machinability and residual stresses evolution of LPBF 18Ni300 maraging steel

Abstract

Metal additive manufacturing (MAM) currently allows the production of mechanical components with technical specifications suitable for structural applications with a high level of complexity. Despite the most recent technological developments, additively manufactured parts may still lack the geometrical and dimensional accuracy as well as surface integrity required for precision mechanical assemblies and system reliability. These requirements often lead to post-processing operations through precision machining technologies. The present work focuses on the machinability study of 18Ni300 maraging steel obtained by laser powder bed fusion and its comparison with the conventional counterpart. Milling tests were carried out covering a wide range of cutting parameters, aiming at understanding their influence and comparing the obtained results in terms of cutting force, specific cutting pressure, roughness and chip morphology. In depth residual stresses have been measured for different operational and metallurgical conditions and their comparison was performed. A more significant effect of the feed parameter on the analysed data is noticed, particularly regarding the affected layer depth of the residual stresses due to cutting. Moreover, the higher mechanical strength of the additively manufactured alloy does not translate into an equivalent increase in the required average specific cutting pressure.