Comparative Study of Filament-Fed and Blown Powder-Based Laser Additive Manufacturing for Transparent Magnesium Aluminate Spinel Ceramics

Abstract

Magnesium aluminate spinel is of great interest as a transparent ceramic for its excellent mechanical properties and excellent optical transmittance. Additive manufacturing of this desirable material presents several benefits over traditional manufacturing methods, including reduced fabrication time and cost and the potential to fabricate structures with complex geometries and internal cooling networks. Despite the many benefits, the challenges hindering this technology must be overcome. A primary challenge with powder-based laser additive manufacturing of transparent ceramics is a trade-off between densification and cracking. The fabrication of transparent ceramics requires nearly full densification since pores act as light scattering centers. Even relatively small percentages of porosity render ceramics translucent or opaque. Previous studies on powder-based laser direct deposition of spinel ceramics have shown that densification to transparency is possible with high-laser power deposition. While high-laser powers are beneficial for densification, it also produces high thermal gradients that result in significant crack formation. Cracks hinder mechanical properties and transparency, limiting possible applications. Thus, we propose a filament-based deposition strategy to reduce laser power requirements. Filament-fed laser direct deposition, instead of blown powder, dramatically reduced the amount of gas porosity within the melt. Hence, highly densified, transparent, spinel ceramics were fabricated. Through decreased laser power requirements for high densification, cracking was largely reduced. This paper provides a comprehensive comparison between filament- and powder-based laser direct deposition by analyzing important sample characteristics, including porosity, cracking, grain size, and their controlling mechanisms. This paper also presents a laser direct deposition and postprocessing method to manufacture predensified spinel filaments.

Department(s)

Mechanical and Aerospace Engineering

Comments

U.S. Department of Education, Grant P200A180061

Keywords and Phrases

Additive Manufacturing; Filament-Fed; Laser Direct Deposition; Magnesium Aluminate Spinel; Transparent Ceramics

International Standard Serial Number (ISSN)

1042-346X

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2021 Laser Institute of America, All rights reserved.

Publication Date

01 Nov 2021

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