Effect of duplex surface treatment on the impact properties of maraging steel produced by laser powder bed fusion

The impact properties of an L-PBF 18Ni-300 maraging steel were investigated after different heat and duplex (nitriding and PVD coating) surface treatments. Impact energy is almost isotropic. Contrary to expectations, impact energy is not decreased by surface treatments, since the effect of surface embrittlement of nitriding is compensated by the increase in the austenite content. An important role is played by the geometry of the notch where the surface hardening is lower than in the flat surface of the Charpy specimens.