Alloying Effects on the Microstructure and Properties of Laser Additively Manufactured Tungsten Materials

TL;DR

This study investigates how alloying tungsten with ZrC and NiFe via laser additive manufacturing improves microstructure stability, toughness, and hardness, addressing previous issues like cracking and embrittlement.

Contribution

It introduces a novel alloying approach combining ZrC and NiFe to enhance tungsten's microstructure and mechanical properties in additive manufacturing.

Findings

ZrC promotes microstructural stability and increases hardness through ZrO2 dispersoids.

NiFe enhances toughness by forming micron-scale FCC phases within BCC tungsten.

The combined WNiFe+ZrC system achieves improved stability and performance in laser AM tungsten.

Abstract

A large body of literature within the additive manufacturing (AM) community has focused on successfully creating stable tungsten (W) microstructures due to significant interest in its application for extreme environments. However, solidification cracking and additional embrittling features at grain boundaries have resulted in poorly performing microstructures, stymying the application of AM as a manufacturing technique for W. Several alloying strategies, such as ceramic particles and ductile elements, have emerged with the promise to eliminate solidification cracking while simultaneously enhancing stability against recrystallization. In this work, we provide new insights regarding the defects and microstructural features that result from the introduction of ZrC for grain refinement and NiFe as a ductile reinforcement phase - in addition to the resulting thermophysical and mechanical properties. ZrC is shown to promote microstructural stability with increased hardness due to the formation of ZrO2 dispersoids. Conversely, NiFe forms into micron-scale FCC phase regions within a BCC W matrix, producing enhanced toughness relative to pure AM W. A combination of these effects is realized in the WNiFe+ZrC system and demonstrates that complex chemical environments coupled with the tuning of AM microstructures provides an effective pathway for enabling laser AM W materials with enhanced stability and performance.