Understanding the microstructure and mechanical properties of IN738LC fabricated by laser powder bed fusion at different partition lengths

Abstract

The adoption of a partition scanning strategy during laser powder bed fusion (LPBF) is one of the main ways to relieve residual stress and refine the grain. In this work, the IN738LC alloy samples were fabricated by island and linear scanning strategies at different partition lengths (PL). The effect of different PLs on forming quality, microstructure, and mechanical properties was investigated. The results indicated that the densification decreased, and the surface became rough showing more balling defects with increasing PL. With the increase of PL from 2.5 mm to 15 mm, the primary dendrite arm spacing (PDAS) increased by 50% and 84%, average grain size increased by 25% and 24%, and high-angle grain boundaries (HAGB) decreased by 24.1% and 17.7% for RL and IS scanning strategies. The combination of the high-temperature gradient, high cooling rate, and complex remelting at small PL weakens the texture and increases the anisotropy. The excellent mechanical properties were obtained at the rotating line (RL) scanning strategy with a partition size of 2.5 mm. The microhardness, ultimate tensile strength (UTS) and elongation (El) reached 470.7 HV, 1598 MPa, 14.2%.