Effect of In-Situ Pulse Current on Microstructure and Mechanical Properties of Aisi 9310 Gear Steel by Laser Powder Directed Energy Deposition

Abstract

AISI 9310 gear steel is a widely used high hardenability material for aerospace gear components. Laser Powder Directed Energy Deposition (LP-DED) is an advanced manufacturing technology that utilizes a laser heat source to melt metal powder, creating a molten pool and rapidly achieving material deposition and shaping. It has advantages of high convenience and rapid forming, making it suitable for producing lightweight and high-strength aerospace parts. However, the forming quality has constrained the development of LP-DED. To solve this problem, this research improves LP-DED by assisted application of in-situ pulsed current to prepare high-quality deposited specimens. Pulsed current does not induce phase transformation in the deposition zone, but the Joule heating effect introduced by the current drives grain growth. The electric-plastic effect of pulsed current leads to increased plastic deformation, additionally transforming dislocation defects from dislocation lines to dislocation networks, and significantly increasing dislocation density. The current-induced contraction force compresses the molten pool and accelerates the gas discharge, effectively reducing the porosity and the number of pores, which improves comprehensive mechanical properties. This research contributes to the microstructure modification and property optimization of gear steel prepared by pulsed current-assisted LP-DED.

Keywords: Laser powder directed energy deposition, Gear steel, Pulse current, Characterization