A New Technique for Chemistry at the Scale of Printing and Bulk Composition Analysis

This work demonstrates and evaluates a new technology for chemical characterization of additive manufacturing metals. The process of rapidly melting and solidifying materials can affect chemical properties and impact part performance. Despite its importance, performing chemical characterization is difficult and time-consuming. For most metals, it requires 3-4 different analytical techniques and standard test methods. Addressing the limitations of current instruments, the innovative technology combines Laser Ablation, Laser Ionization (LALI) with Time-of-Flight Mass Spectrometry (TOF-MS). The work’s first part compares results quantified by LALI-TOF-MS with those obtained by other analytical techniques. For a set of additive manufacturing metals, it will compare accuracy and precision and discuss any discrepancies between different techniques. The second part of this work demonstrates the technology’s chemical mapping capabilities. This includes results from a variety of case studies that reveal local heterogeneities in elemental and oxide composition.

LALI-TOF-MS combines a dual-laser ionization system with a TOF mass analyzer and provides trace-level quantification for virtually the entire periodic table. The LALI ionization source analyzes solid samples directly, eliminating the complicated sample preparation procedures required by other techniques. For additive manufacturing metal applications, solid samples include printed parts or pelletized powders. The instrument’s versatility supports 1) rapid quality control of virgin and reused feedstock powders, 2) development of new materials specifically suited for additive manufacturing, and 3) investigating chemical variations across heterogeneous materials and failed parts. LALI-TOF-MS can provide bulk quantification of a metal’s elemental composition and it can quantify interstitial elements like carbon, nitrogen, and oxygen that generally require other instrumentation. Additionally, it can perform elemental mapping, identifying both spatial distributions and depth profiles of any element of interest. With a spatial resolution ranging from 5-200 microns, LALI-TOF-MS provides chemical data at the particle level and the same scale as the melt pool in many additive manufacturing techniques.