Microstructure evolution and corrosion behavior of the novel maraging stainless steel manufactured by selective laser melting

The effects of selective laser melting (SLM) processing parameters on the microstructure and corrosion behavior of CX (Corrax) stainless steel were investigated via microstructure characterization, electrochemical tests and passive layer analysis. Different processing parameters (including the laser power of 150-170 W and scanning speed of 0.9–1.3 m·s−1) were used to manufacture the SLMed CX samples. The results revealed that the relative density of SLMed CX samples reached above 96%, which exhibited a higher densification effect. Besides that, the SLMed CX samples had the high-density of geometrically necessary dislocations (GNDs, ranging from 9.63 × 1014 m−2 to 9.86 × 1014 m−2), and the average grain size mainly distributed within 2 μm, in which the sample S1 (manufactured with P = 170 W, V = 0.9 m·s−1) exhibited the smallest average grain size of 1.1 μm. The proportion of Σ3 boundaries varied slightly in samples, ranging from 4.13% to 4.87%, which was positively correlated with the content of recrystallization. In addition, the electrochemical test results indicated that the scanning speed had a greater effect on corrosion resistance of SLMed CX samples, comparing with the laser power. The sample S1 exhibited both the largest relative density of 99.13% and the best corrosion resistance, including the largest value of corrosion potential (ECorr, −259 ± 12mVSCE) and the lowest value of corrosion current density (ICorr, 0.484 ± 0.012 μA·cm−2). The corrosion resistance of SLMed CX sample was ascribed to the synergistic effects of its relative density, grain size, grain boundary character distribution and GNDs density, and these influence factors were also discussed in detail.