Densification behavior, microstructural evolution, and mechanical properties of TiC/AISI420 stainless steel composites fabricated by selective laser melting

AISI 420 martensitic stainless steel with excellent corrosion resistance is an ideal choice for plastic injection molds. However, injection molds are easy to fail in high–intensity and high-pressure environments. Therefore, it's necessary to improve their hardness and tensile strength to prolong the service life of injection molds. In this work, Selective laser melting (SLM), an additive manufacturing technology was utilized to process 5 wt% TiC/AISI 420 composites. The influence of volumetric energy density (η) on relative density, constitutional phases, microstructure and mechanical properties were investigated. The results indicated that insufficient energy input could cause defects such as pores and crack in the parts, while a part with near-full density could be fabricated if the applied η was properly settled. The ring-like structure that was comprised of thin “metal-ceramic” interface along the grain boundary was distributed more uniform with the increase of applied η. The SLM-processed sample showed a best mechanical properties at highly applied η (320 W, 850 mm/s, η = 85.6 J/mm3). It had an elevated micro-hardness (592.2 ± 53.6 Hv), an enhanced tensile strength (1452.5 MPa) and an improved elongation (8.65%), which was higher than that of the cast AISI 420 stainless steel. The research would provide theoretical support for the application of SLM-processed AISI420 stainless steel composites.