DOCTOR OF PHILOSOPHY

on Wednesday, September 6, 2023

1:00 PM

 DISSERTATION PROPOSAL DEFENSE

will be held for

Nathaniel Lies

In-person at GTMI 114

Or online at: Click here to join the meeting

THE DEVELOPMENT OF HIGH-TEMPERATURE MOLYBDENUM ALLOYS MANUFACTURABLE VIA POWDER BLOWN LASER DIRECTED ENERGY DEPOSITION ADDITIVE MANUFACTURING

Committee:

Prof. Aaron Stebner, MSE/ME (advisor)

Prof. Arun Gokhale, MSE

Prof. Josh Kacher, MSE

Prof. Richard Neu, ME/MSE

Prof. Stefano Curtarolo, Duke University, MEMS

Dr. Dan Driemeyer, Boeing

Abstract

Molybdenum (Mo) alloys have long been limited in their use by low room temperature ductility and oxidation concerns. Despite these issues, Mo has found valuable application in several industries requiring high temperature materials such as aerospace, nuclear power, and metalworking fixtures. The geometric freedom and atmospheric control of powder blown laser directed energy deposition additive manufacturing (DED-LB) makes it an attractive choice for expanding applications of Mo alloys. This work explores three main avenues of improving the additive manufacturability of Mo: (1) improving ductility, (2) inoculation, (3) local compositional control. First, increasing ductility via alloying additions can reduce issues such as thermal cracking and delamination of the part from the substrate during printing. Potential alloying additions will be investigated through an integrated computational materials engineering (ICME) framework and verified with a repeatable casting process and mechanical testing before being additively manufactured. Second, inoculation has been shown to improve the properties of cast and additively manufactured alloys, especially high temperature strength. An ICME framework will be used to predict beneficial non-metallic additions to alloys that will be printed, mechanically tested, and compared with results from goal 1. Third, leveraging local compositional control in DED-LB will allow for alloys identified in previous sections to be used in conjunction with an oxidation resistant cladding to demonstrate additive manufacturing's unique capability to produce optimized Mo components.