Comparative study of the microstructure between a laser beam melted 17-4PH stainless steel and its conventional counterpart

The aim of this work was to compare the microstructures 17-4PH martensitic stainless steels (MSSs) obtained by conventional manufacturing (CM), and additive (AM) using laser beam melting (LBM) process. Both materials were studied after same H900 heat treatment. Significant differences in microstructure observed between two MSSs, with a higher austenite content for AM-H900 sample, as compared CM-H900 sample. Transmission electron microscopy (TEM) analyses allowed identify both retained reversed but most part detected found be austenite. high amount sample attributed heterogeneous distribution austenite-stabilising elements solution treated AM leading decrease Ms value subsequent increase driving force martensite transformation during ageing at 480 °C. Moreover, TEM highlighted thinner laths steel one. This interpreted an nucleation sites growth rate Despite those microstructure, samples showed similar tensile behaviour, UTS Rp0.2 values, strain fracture probably related pores and/or intergranular carbides.