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Title:	2-component powder injection moulding (2C-PIM) of stainless steel (SS17-4PH) and yttria stabilized zirconia (3YSZ)
Authors:	Bonaventure Emeka Ukwueze (P75173)
Supervisor:	Abu Bakar Sulong, Assoc. Prof. Dr.
Keywords:	Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia Molding (Founding) Molding materials Zirconium oxide
Issue Date:	8-May-2019
Description:	Due to growing need for multifunctional and high performance devices in modern engineering applications, there is increasing concern for development of advanced materials with new functions or properties. These functions are difficult to accomplish using conventional powder injection moulding (PIM) or other machining /casting processes or with traditional materials. Thus, 2C-PIM is a unique choice for production of intricate geometries of metal-ceramic composites in high production units. However, this technique is often challenging due to limitations imposed by the incompatibility in the physical and thermal properties of the dissimilar materials. The objectives are to investigate the rheological properties and evaluate the feasibility of processing the bimaterials from 17-4PH and 3YSZ feedstock. Furthermore, to develop the solvent/ thermal de-binding process and establish the optimum time for solvent de-binding including influence of other parameters. The effect of sintering temperatures on the bonding mechanisms, microstructure and mechanical /physical properties of final part were studied. Four feedstocks with optimal powder loading 69vol%, 68vol% for 17- 4PH and 51vol%, 50vol% for 3YSZ were prepared. Two binder system of Palm stearin (PS) and Low-density polyethylene (LDPE) were utilized as a binder system in the ratio of 60wt%/40wt%. The feedstock mixing was performed using Brabender mixer and the rheological behavior investigated under a temperature of 130oC, 150oC and 180oC using Schmidaz capillary rheometer. The rheological results indicated pseudo- plastic and shear thinning behaviour acceptable for PIM. The feedstocks were processed in sequence using screw type injection moulding to form a bi-material. Solvent extraction of the palm stearin binder was performed in acetone. Thermal de-binding of the remaining binder component was performed in two steps in a split furnace under argon atmosphere. The sintering of bi-material of 17-4PH and 3YSZ were conducted by isothermal sintering in vacuum at 1250oC, 1300oC and 1350oC. The single materials of SS17-4PH and 3YSZ were subsequently sintered under the same conditions. Heating rates of 2oC/min, 3oC/min, 5oC were applied. The densities of the sintered samples were measured using Archimedes method. The densities for SS17-4PH and 3YSZ indicated 95% - 97% and 93% - 97% respectively. The result indicated that linear shrinkage of the bi-materials increased from 10% to 12% while density improved from 95% to 97%. The SEM and FESEM analysis showed the bonding appeared sound with no flaws. The XRD patterns depicted sharp crystalline structure attributable to cubic structure of chromium iron nickel and tetragonal phase structure of zirconium yttrium oxide at the interface. EDX line and layered spectrum analysis showed presence of Fe, Cr, Ni, and Zr at the interface which resulted in bonding due to formation of oxide layer and metallic phases during co-sintering. The microstructure depicted the tetragonal structure of 3YSZ on one part and martensitic ferritic structure of 17-4PH on the other part. The distribution of hardness values showed that regions closer to the interface have higher value than regions farther from it. The tensile (bonding) strength of the bi-materials were also determined and fall within the range of 39.65 to 48.7MPa. The carbon contamination is minimal. Therefore, the development of a bimaterial structure of stainless steel and zirconia via 2C-PIM process was successful.,Ph.D.
Pages:	192
Call Number:	TS243.5.U559 2019 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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