Exploration of microstructure, mechanical, and corrosion properties in selective laser melting TiN/AISI 420 composites with diverse TiN reinforcement particle sizes

Metal matrix composites (MMCs), defined as metal matrices reinforced by ceramic particles, are manufactured by selective laser melting process (SLM), delivering outstanding performance. This research examines the influence of reinforcement Titanium Nitride (TiN) particle size on the performance of martensitic stainless steel (AISI 420) matrix fabricated via SLM. Initially, one in weight percentage of TiN particles of varying sizes (20 µm, 2 µm, and 20 nm) were incorporated into the AISI 420 matrix, using a hybrid wet mixing method to ensure homogeneous dispersion and mitigate particle agglomeration and contamination. The microstructure, mechanical, and corrosion properties of the SLM TiN/AISI 420 samples were subsequently analyzed. The results revealed that samples reinforced with 20 nm TiN particles exhibited optimal performance, achieving a hardness of 746 ± 5 HV, a tensile strength of 1671 ± 15 MPa, and an elongation of 5.79 ± 0.13. These values surpass those of samples reinforced with 2 μm TiN and 20 μm TiN particles. The uniform distribution of fine TiN particles within the matrix, which effectively reducing grain size, significantly contributed to these results. Furthermore, the 20 nm TiN/AISI 420 samples also exhibited superior corrosion resistance in seawater solution, with a corrosion rate of 1.17 ± 0.01 µm year −1 — 59% and 80% lower than the 2 μm and 20 μm TiN/AISI 420 samples, respectively. This enhancement in corrosion resistance is attributed to the high content of retained austenite and the presence of TiN particles, which improve the continuity and stability of the passive oxide layer. Graphical abstract