Effect of ZrH2 particles on the microstructure and mechanical properties of IN718 manufactured by selective laser melting

TL;DR

This study investigates how ZrH2 particles affect the microstructure and mechanical properties of IN718 alloy produced by selective laser melting, revealing increased strength and anisotropic behavior influenced by processing and heat treatment.

Contribution

It demonstrates that ZrH2 addition creates Zr-rich particles without altering microstructure, enhancing strength, and analyzes anisotropic mechanical properties related to texture.

Findings

ZrH2 particles increase alloy strength at room and high temperatures.

Heat treatments produce gamma'' precipitates controlling strength.

Mechanical anisotropy is linked to texture orientation.

Abstract

The influence of Zr additions (in the form of ZrH2 particles) on the microstructure and mechanical properties of IN718 Ni-based superalloy manufactured by selective laser melting was explored. Fully dense alloys could be obtained by careful selection of the processing parameters. The addition of ZrH2 did not modify the microstructure of the alloy but introduced a dispersion of Zr-rich globular particles of approximately 50 nm in diameter which increased the strength of the as-printed material at ambient (23C) and high temperature (550C). Heat treatments of solubilisation followed by aging led to a fine dispersion of gamma" precipitates that controlled the strength of the alloy, which was independent of the addition of Zr. Moreover, dynamic strain ageing was found in the heat treated materials when deformed at 550C. Finally, the strength of the IN718 deformed perpendicular to the building direction was higher than that along the building direction, regardless of the heat treatment and temperature. Computational homogenization simulations showed that the anisotropy was associated with the strong texture.