Enhancing corrosion resistance of additive manufactured heterogeneous martensite stainless steel by hot isostatic pressing

Abstract

The effect of hot isostatic pressing (HIP) on microstructure, corrosion resistance and passive film characteristics for heterogeneous martensite stainless steel (MSS) manufactured by laser powder bed fusion (LPBF) was studied. The microstructure was mainly typical original austenite grains and martensite laths and the high content of austenite disappeared after HIP. The average grain size (about 14.09 μm) was larger than that of sample before HIP (about 4.33 μm). When the laser power was 170 W and the scanning speed was 550 mm·s−1, the density of the samples after HIP increased to >99.99%. When the scanning speed increased to 1250 mm·s−1, the density of samples increased from 97.82% to 99.89%. After HIP treatment, the passivation trend of low density (97.8%) samples was more obvious and the pitting potential increased from −44 mVSCE to 179 mVSCE. The pitting potential of high density (99.77%) samples increased from 265 mVSCE to 291 mVSCE and the electrochemical impedance value increased. The sensitivity of the samples to chloride ions significantly decreases after HIP. The donor density for sample before HIP was 2.5546 × 1020 cm−3, which was higher than that of sample after HIP (2.001 × 1020 cm−3). Therefore, the corrosion resistance of LPBF high strength stainless steel was enhanced after HIP.