Mohamed Imbaby

Net shape fabrication of stainless-steel micro machine components from metallic powder

A fabrication process of the net shape 316-L stainless-steel micro machine components is reported. The fabrication process combines softlithography and powder metallurgy to produce microcomponents of complex geometries of high quality. The process starts with softlithography by producing ultra thick SU-8 master moulds and their negative replicas of polydimethylsiloxane (PDMS). Then stainless-steel slurry is prepared by mixing super fine 316-L steel powder and binder to fill the PDMS moulds. The two binders used in the experiments were Duramax D-3005 and a mixture of B1000 and B1007. The PDMS micro moulds are filled with the metallic slurries and green parts are obtained from de-moulding, before going through de-binding and sintering in forming gas atmosphere. The fabrication steps were repeatedly tested. The resultant micro parts show high quality shape retention which is attributed to the quality of the SU-8 master moulds. The hardness property of the sintered microcomponents was tested with a micro indenter and a 200 g load was applied. The Vickers hardness of the sintered components was found to be about 255, which was higher than 225 of annealed 316L stainless steel and the two binders make little difference on the hardness of the sintered samples.

Net shape fabrication of stainless steel-alumina composite micro parts

This paper presents a successful method to fabricate high-quality composite micro parts. The fabrication process starts with producing SU-8 aster moulds using photolithography technique, mirror replication of PDMS soft moulds, preparing composite slurry using super fine 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, de-binding and sintering. A new method was used in this research to homogenize the alumina particles in a stainless steel composite slurry. Stainless steel and alumina powders were dispersed separately in distilled water and dispersant. Then, the two dispersed powders were mixed together to form a homogeneous composite slurry. The process resulted in high-quality composite micro parts which retain the very details of the SU-8 master moulds. The internal structures of the green and sintered micro parts showed homogeneous distribution of alumina particles in a stainless steel matrix. The density and micro hardness of the sintered parts were also investigated in detail for different stainless steel alumina compositions.

A Fabrication Process of Composite Micro Components using Super Fine Stainless Steel and Ceramic Nano Powders

Fabrication of micro components from different monolithic materials such as ceramics, metals, and polymers have been discussed before [Jun et al., 2008; Mohamed et al., 2008; Bong-Kee & Tai, 2008], but hardly any research has been reported in fabrication of composite microparts [Ping et al., 2008; Hany & Kyle, 2009; Su-Jin et al., 2008]. This chapter introduces a novel approach to fabricate stainless steel ceramic composite micro machine components. The two types of composites to be introduced are stainless steel-alumina and stainless steel-titania. Three types of powders were tested, including 5 μm stainless steel, 400 nm alumina and 320 nm titania. Four different compositions prepared for each composite type are 2.5, 5, 7.5 and 10% weight of ceramic. Characterization of composite micro components in terms of slurry preparation process, sintering conditions, shape retention, density, linear shrinkage and micro hardness is reported in detail. The fabrication process is divided into three stages. In the first stage, SU-8 master moulds and their negative replica soft moulds are produced using softlithography process. The second stage includes preparation of composite slurries, filling soft micro moulds and obtaining composite green micro components. In the third stage, the composite green micro components are de-bound and sintered in vacuum and nitrogen-hydrogen mixture (90% nitrogen and 10% hydrogen) respectively at 1350 oC. Afterwards, the properties of sintered micro components are studied in detail.

Micro Machine Parts Fabricated from Aqueous Based Stainless Steel Slurry

A fabrication process of stainless steel micro components from metallic powder is reported. The process consists of two stages. In the first stage, high quality SU-8 master moulds and their negative replicas from soft moulds are produced using photolithography and soft moulding techniques respectively. The second stage includes preparation of stainless steel slurry, filling the soft mould, obtaining the green parts, de-binding and sintering to the finial parts. A method is proposed in this research to obtain the optimum dispersant for preparation of the metallic slurry and the result was found to be 0.003 (dispersant/powder wt.). Both vacuum and forming gas atmosphere sintering conditions were investigated. The results show micro components have the similar high quality as the master moulds. The maximum sintered density was found to be 98.1% when the sample was sintered at 1, 350 ∘C in vacuum.