Fabrication of free standing 316-L stainless steel–Al2O3 composite micro machine parts by soft moulding

This paper presents a successful method for fabricating high-quality stainless steel–alumina composite micro machine parts using a soft moulding technique. The fabrication process starts with the production of SU-8 master moulds using a photolithography technique, followed by mirror replication of PDMS soft moulds, preparation of composite slurry using superfine 316-L stainless steel (5 μm) and α-alumina powder (⩽400 nm) in 2.5, 5, 7.5 and 10 wt.%, filling the moulds, obtaining the green parts, debinding and sintering. The fabrication process was investigated in detail and the optimum dispersant and binder was obtained. The process resulted in high-quality composite micro parts that retain the very detailed features of the SU-8 master moulds. The density and micro hardness of the sintered parts were also investigated for the different composite compositions. The hardness of the stainless steel composite was improved by about 1.8 times that of the pure 316-L stainless materials by the addition of 10% alumina.