Effects of TiN content and heat treatment on microstructural changes, mechanical strength, and corrosion resistance in selective laser melting of TiN/AISI 420 composites

Abstract

This study investigates the influence of Titanium Nitride (TiN) concentration variations and heat treatment on the microstructure, strength, and corrosion resistance of TiN/AISI 420 composites fabricated via selective laser melting (SLM). Results demonstrate that the addition of TiN particles (2 μm in size) at 0.5, 1, and 2 wt percent (wt. %) to the AISI 420 alloy enhances the toughness modulus of SLM TiN/AISI 420 to 37.0 ± 1.5 J/m3, 42.2 ± 0.4 J/m3, and 36.2 ± 0.7 J/m3, respectively, surpassing the SLM AISI 420's toughness of 21.3 ± 0.6 J/m3. Moreover, a positive relationship between TiN content and corrosion resistance is observed, with 2 wt % TiN/AISI 420 composites exhibiting the highest resistance at 105.6 ± 2.5 mm/year in a 6 wt % FeCl3 solution. Following heat treatment, a reduction in hardness is noted due to decreased surface residual stress and increased retained austenite. However, treated composites demonstrate improved mechanical and corrosion resistances. Particularly noteworthy is the highest toughness of 118.0 ± 1.3 J/m3 observed in 1 wt % TiN composites and a corrosion rate of 104.7 ± 2.7 mm/year in 2 wt % TiN composites. The homogeneous dispersion of TiN particles and the phenomenon of transformation-induced plasticity significantly enhance toughness, while increased levels of retained austenite contribute to improved corrosion resistance. This work underscores the potential of advanced manufacturing techniques in developing composite materials with diverse applications, such as robotic mold inserts. It emphasizes the pivotal role of composite formulation and post-processing in augmenting material performance.