Selective laser melting of Nano-TiN reinforced 17-4 PH stainless steel: Densification, microstructure and mechanical properties

In this study, TiN-reinforced 17-4 PH stainless steel was produced by selective laser melting (SLM). It was aimed to utilize nano-sized TiN particles both as inoculants to obtain an equiaxed microstructure in as-built condition and as dislocation barriers to improve mechanical properties. SLM process parameters development was conducted for TiN-reinforced 17-4 PH stainless steel powders. Consistent with the literature, it was observed that SLM processing window shifts to higher energy densities with the addition of ceramic particles. Moreover, it was found that smaller point distance values favor continuous melt tracks and thus, higher densities. TiN-reinforced composites were seen to exhibit a very fine and equiaxed microstructure, effectively eliminating directional solidification and consequent anisotropy. Both strength and ductility in as-built condition increased significantly for the TiN-reinforced composites. Strength further increased after heat treatment with a compromise in ductility due to excessive hardening from both TiN particles and Cu-rich precipitates. Yet, TiN incorporation was found promising for high-temperature applications in the future, where standard 17-4 PH stainless steel fails due to precipitate coarsening.

Automated summary

TiN-reinforced 17-4 PH stainless steel was produced using selective laser melting (SLM), resulting in a fine and equiaxed microstructure with improved mechanical properties. The addition of TiN particles shifted the SLM processing window to higher energy densities. The incorporation of TiN was found promising for high-temperature applications in the future.