A Mechanistic Study on Environment Gases in Metal Additive Manufacturing

TL;DR

This study investigates how different environmental gases affect laser-based metal additive manufacturing, revealing how gases like helium influence cooling, defect formation, and part quality through advanced imaging techniques.

Contribution

It provides new insights into the effects of various gases on critical AM phenomena, guiding strategic gas selection for improved manufacturing outcomes.

Findings

Helium has negligible cooling effect compared to argon.

Helium suppresses unstable keyholes and reduces pore size.

Environmental gases significantly influence defect formation in laser AM.

Abstract

A variety of protective or reactive environmental gases have recently gained growing attention in laser-based metal additive manufacturing (AM) technologies due to their unique thermophysical properties and the potential improvements they can bring to the build processes. However, much remains unclear regarding the effects of different gas environments on critical phenomena in laser AM, such as rapid cooling, energy coupling, and defect generation. Through simultaneous high-speed synchrotron x-ray imaging and thermal imaging, we identify distinct effects of various environmental gases in laser AM and gained a deeper understanding of the underlying mechanisms. Compared to the commonly used protective gas, argon, it is found that helium has a negligible effect on cooling the part. However, helium can suppress unstable keyholes by decreasing effective energy absorption, thus mitigating keyhole porosity generation and reducing pore size under certain processing conditions. These observations provide guidelines for the strategic use of environmental gases in laser AM to produce parts with improved quality.