Effect of processing gas on spatter generation and oxidation of TiAl6V4 alloy in laser powder bed fusion process

Abstract

The atmosphere is a vital factor influencing powder degradation during laser powder bed fusion. Particularly, its purity, density, and thermal conductivity, can strongly affect spatter generation, thermal history, and oxidation. It is critical to understand the atmosphere-spatter properties relationship to enhance powder recyclability and overall process sustainability. Herein, the effect of processing gases, among pure Ar, (Ar+He), and He, on spatter generation and oxidation during TiAl6V4 processing is investigated. To evaluate their influence on impurity pickup and morphology of spatters, bulk chemical analysis and scanning electron microscopy were conducted. The nature and thickness of surface oxides on spatters were comprehensively examined using surface analysis tools including X-ray photoelectron spectroscopy, Auger electron spectroscopy, and nano secondary ion mass spectroscopy. The bulk chemical analysis showed a 70% increase in oxygen content and a 3-fold increase in nitrogen content from virgin to spatter collected in standard argon atmosphere. The increase of impurities was substantially lower for the spatters generated in He and the mixture of (Ar+He). The surface analysis showed that the spatter surface was covered with a uniform Ti- and Al-rich oxide layer along with Al-based oxide particulates. Finally, this study discusses the nature of oxide on TiAl6V4 spatters.