Embedding ceramic components in metal structures with hybrid directed energy deposition

Abstract

The combined bene t of both additive and subtractive manufacturing within the same gantry system enables hybrid directed energy deposition to create complex geometries with smooth surface nish and superior dimensional accuracy. Moreover, with layer-by-layer access to the structure during both the addition and subtraction of material, the insertion of components is now possible, assuming the components can survive the high temperatures associated with the subsequent metal deposition. Ceramic inserts are of interest for a variety of reasons including: (1) to create complex interwoven ductile / brittle composites for ballistics, or (2) to integrate high temperature strain or temperature sensors protected within ceramic substrate subsumed into a larger metal structure. In this work, steel substrates were machined to create an internal cavity for insertion of a ceramic component. During the investigation of several different over-the-ceramic deposition strategies, components were inserted and different sequences were continued to envelop the inserted ceramic with varying success. Unmelted powder served as both a thermal buffer and to provide a ush surface upon which the laser cladding could continue. Subsequent depositions were attempted with both dry and wet powder (addition of machining coolant to wet) providing stability and minimizing displacement caused by the gas ow. Finally, the use of an oblique angle for laser cladding allowed for the redirection of some fraction of the introduced thermal energy away from the ceramic, and consequently, improved the survival of the inserts. With this combination of techniques, ceramic inserts survived full embedding within a complex steel structure.