Integration of High Productivity and Mechanical Properties of AISI 420 Stainless Steel Processed by Laser Powder Bed Fusion

Abstract

The high cost and time consumption seriously hinder industrial applications of laser powder bed fusion (LPBF) technology. Increasing layer thickness is an effective strategy to enhance productivity. This study investigated the effect of layer thickness under comparable volumetric energy density in LPBF-processed AISI 420 stainless steels. The results show that relative densities exceeding 99.8% are achieved in all the samples. A duplex microstructure comprising a martensitic matrix and retained austenite is observed in the as-built specimens, with the retained austenite content increasing from 17.6 to 30.9% as the layer thickness increased from 40 to 80 μm. Subsequent austenitizing and tempering heat treatments result in the complete transformation of retained austenite into tempered martensite. The specimen manufactured from 80 μm layer thickness exhibits an excellent ultimate tensile strength of 1437 MPa along with an outstanding elongation of 12% after heat treatment. The enhanced mechanical performance is attributed to the decomposition of retained austenite and the formation of finely tempered martensite during heat treatment. This work demonstrates that by optimizing process and post-processing parameters, both productivity and mechanical properties can be simultaneously improved in LPBF-fabricated AISI 420 stainless steels, providing a promising pathway toward high-performance and high-efficiency additive manufacturing.