Effects of nitriding on salt spray corrosion resistance of additively manufactured 17-4 PH steels

This work addresses the effects of varying nitriding temperatures of 530, 560 and 580 °C for 2 h on corrosion resistance of additively manufactured (AM) 17-4 PH steels, using neutral salt spray (NSS) method for 104 h. The morphological analysis indicated the presence of columnar grains along the built direction of additive manufacturing process. The refined grain size and the amount of the precipitates increased with an increasing nitriding temperature. The results of the analysis showed that a minimum weight loss was observed at 580 °C, due to the formation of passive oxide layer and nitrogen rich precipitates on the surface. The X-ray diffraction (XRD) showed the presence of these compounds: Cr2N, (Fe, Cr)4N, (Fe, Cr)2-3N, Fe2O3, FeOOH, and Cr2O3 on the nitrided sample after the salt spray test.