Negative additive manufacturing of Al2O3-Al cermet material by fused deposition and Direct Ink Writing

Abstract

Although additive manufacturing is an attractive alternative for the manufacturing of complex ceramic geom-etries, the manufactured parts have low mechanical properties due to low solid loading, high porosity, and geometrical distortions. Introducing ductile metal particles into the brittle ceramic matrix is an effective tech-nique to enhance the geometrical accuracy and mechanical properties of the printed part. In the current research, the Direct Ink Writing technique is used to fabricate alumina-based matrix composite reinforced with Al particles by negative additive manufacturing. A homogenous cermet mixture in the form of Al2O3-Al with various Al compositions (5 vol%, 10 vol%, 15 vol%, and 20. vol%) was achieved by high-energy ball milling. A slurry was prepared by mixing the milled powder with the carboxymethyl cellulose binder and sodium silicate in the deionized water. Rheological measurements of all the slurries were carried out to investigate the shear-thinning behavior of the pastes. The slurry was cast into the polylactic acid mold as the mold was built up layer by layer simultaneously using a Mitsubishi robotic manipulator. The printed parts were dried, demolded by dissolving in Dichloromethane (DCM) solution, and sintered at 1400 degrees C for 6 h. X-ray diffraction results revealed two distinguished phases (ceramic and metal) in the finished part. It is possible to formulate printable alumina -aluminum cermet slurries with solid content as high as 50 vol% and 97 % density. It was found that by the inclusion of metallic Al phase, the micro-hardness reduces as compared to monolithic alumina ceramic.