Development of a New Tooling Steel (L40) for Laser Powder Bed Fusion: Influence of Particle Size Distribution and Powder Atomization on Mechanical Performance

Abstract

Additive manufacturing (AM) is widely used for tooling applications: Complex conformal cooling channels are designed to increase and homogenize the cooling rate of a mold insert. The list of available steel grades in laser powder bed fusion is currently very limited and does not satisfy highly mechanically demanding applications; hard stainless steel metals printable without cracking are lacking. Herein, the influence of the particle size distribution and atomization process on the printability of a new tooling steel tailored for AM (L40) is observed on an EOS M290 printer based on microstructural observations and mechanical testing. Several batches with different powder size distributions of either gas‐ or water‐atomized powder are processed and studied. The aim of using water‐atomized powder is to reduce both the environmental footprint and the cost of the feed material. Dense built parts (other 99% density) are achieved using water‐ and gas‐atomized powders. The hardness is in all cases superior to 50 HRC, which is above the standard requirement for injection molding applications. The ductility of gas‐atomized parts is four times higher than that measured on heat‐treated maraging steel. Water‐atomized samples reach a ductility similar to that of maraging steel.

Effects of channel contour laser strategies on fatigue properties and residual stresses of laser powder bed printed maraging steel

“…Figure 1). Maraging 300 (X2NiCoMo18-9-5) is the alloy widely used for this application [8,9] because of its high ductility before heat treatment, its high strength, good hardness [10] and dimensional stability during ageing [11] even though stainless grades are also available for this application [12], [13], [14]. LPBF remains most widely used technology for this application even though Direct Energy Depostion has also been used [15,16,17].…”