Delamination mitigation in additively manufactured Al₂O₃ via enhanced thermal postprocessing

Abstract

Manufacturing thick (>10 mm) alumina (Al2O3) parts through the ceramic additive manufacturing technique of digital light processing (DLP) is difficult due to the large amount of polymer that must be removed. Nearly 35–65 vol% of a fugitive UV‐curable polymer is used in commercial ceramic slurries in order to maintain shape through the DLP process. During the thermal debind, gases form and escape quickly due to pressure build‐up, leading to defects in the form of print layer delamination. Here, we analyze the polymer decomposition through thermogravimetric analysis in order to design a less aggressive thermal debind schedule through strategic thermal holds and decreased heating rates. The new schedule led to a 83% reduction in average delaminations per sample (from 6.9 delaminations per sample to 1.2 delaminations per sample) and up to a 100% increase in wall thickness (from nominally 10–20 mm). A complex, Al2O3 turbine rotor (with maximum wall thickness of 5 mm in the center hub section) of a JetCat P400 engine was fabricated to compare the new schedule to the manufacturer provided one. The improved thermal debind schedule produced a turbine rotor with no observable delamination defects.