Cold Isostatic Pressing to Improve the Mechanical Performance of Additively Manufactured Metallic Components

TL;DR

This study demonstrates that cold isostatic pressing significantly enhances the mechanical strength and capacity of additively manufactured AISI 316L stainless steel components by reducing porosity and maintaining isotropic microstructure.

Contribution

The paper introduces a novel post-processing technique, cold isostatic pressing, to improve the mechanical properties of 3D printed metallic parts, which was not previously explored for this purpose.

Findings

CIP increases yield load and maximum capacity of 3D printed steel.

Porosity is reduced and microstructure remains isotropic after CIP.

Material exhibits homogeneous properties regardless of layer orientation.

Abstract

Additive manufacturing is becoming a technique with great prospects for the production of components with new designs or shapes that are difficult to obtain by conventional manufacturing methods. One of the most promising techniques for printing metallic components is binder jetting, due to its time efficiency and its ability to generate complex parts. In this process, a liquid binding agent is selectively deposited to adhere the powder particles of the printing material. Once the metallic piece is generated, it undergoes a subsequent process of curing and sintering to increase its density (hot isostatic pressing). In this work, we propose subjecting the manufactured component to an additional post-processing treatment involving the application of a high hydrostatic pressure (5000 bar) at room temperature. This post-processing technique, so-called cold isostatic pressing (CIP), is shown to increase the yield load and the maximum carrying capacity of an additively manufactured AISI 316L stainless steel. The mechanical properties, with and without CIP processing, are estimated by means of the small punch test, a suitable experimental technique to assess the mechanical response of small samples. In addition, we investigate the porosity and microstructure of the material according to the orientations of layer deposition during the manufacturing process. Our observations reveal a homogeneous distribution independent of these orientations, evidencing thus an isotropic behaviour of the material.