Hybrid Additive Manufacturing and Electric Field‐Assisted Sintering of High‐Temperature Heat Exchangers via Sacrificial Channel Molds

ABSTRACT A hybrid manufacturing approach, integrating additive manufacturing (AM) with electric field‐assisted sintering (EFAS), is developed for fabricating compact heat exchangers (CHXs) from refractory metals. The methodology employed additively manufactured sacrificial channel molds (SCMs) as shapeholders, which are embedded in metal powders using EFAS. Following embedding, the SCMs are chemically dissolved to form CHX internal channels. SCMs are fabricated from chemically reactive, calcium‐based ceramic feedstocks. The microstructure, phase composition, and dissolution behavior of both as‐printed and embedded SCMs are investigated. The shrinkage of the SCMs embedded in refractory metals and the SCM‐metal interfacial characteristics are studied. The results showed that the SCMs containing sufficient chemically reactive ceramics dissolved effectively. The as‐printed SCMs retained the phase composition of their feedstocks, but the embedded SCMs experienced phase changes during embedding. Shrinkage after embedding is strongly dependent on SCM density, with lower density SCMs exhibiting greater shrinkage. A thin SCM‐affected zone is observed at the metal matrix surface, characterized by increased porosity compared to the bulk matrix. This effect is attributed to infiltration of the SCMs into powder particle boundaries under pressure, followed by their dissolution. This study demonstrates the feasibility of manufacturing CHXs from hard‐to‐process refractory metals for use in harsh environments.