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Title:	Two component micro powder injection moulding of bi-material stainless steel 17-4PH and yttria stabilized zirconia
Authors:	Al Basir (P95497)
Supervisor:	Abu Bakar Sulong, Prof. Ir. Dr.
Keywords:	Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia Injection moulding Micro powder Zirconia
Issue Date:	12-Jun-2021
Description:	The global trend towards micro products and the necessity for incorporating different functional capabilities within a micro-component have played a significant role towards the evolvement of the two-component micro-powder injection moulding (2C-μPIM) process. 2C-μPIM technology provides the opportunity to conjugate different materials within one part with complex geometries at mass production. However, the incompatibility between two different materials in terms of physical and thermal properties particularly makes this process challenging. The main objective is to investigate the processability of stainless steel 17-4PH (SS17-4PH) and 3 mol% yttriastabilized zirconia (3YSZ) powders through four main parameters in the 2C-μPIM process. It focuses on the effect of different physical and thermal properties on the feedstocks, injection moulding, debinding, and sintering parameters. In this study, critical powder volume concentration (CPVC) analysis was carried out to determine the optimal powder loadings required to prepare the SS17-4PH and 3YSZ feedstocks. Typically, the feedstocks were obtained by mixing SS17-4PH and 3YSZ powders individually with a binder system comprised of 60 wt.% of palm stearin (PS) and 40 wt.% low-density polyethylene (LDPE). Afterwards, investigations were carried out to evaluate the rheological properties of the prepared feedstocks at temperatures of 140, 160, and 180 �C. The sequential procedures were employed to process the SS17-4PH and 3YSZ feedstocks by using a plunger type injection moulding machine to form micro-sized SS17-4PH/3YSZ green parts. Subsequently, solvent debinding process on the green bi-material micro-parts was carried out in acetone at 70 °C for 40 min. Eventually, thermogravimetric analysis-based thermal debinding process was carried out, and the sintering of the SS 17-4PH/3YSZ micro-sized brown parts were performed in the argon environment at 1250, 1300, and 1350°C at a heating rate of 10 °C/min for sintering time of 1, 2 and 3 hours. In this research work, the obtained CPVC of SS 17- 4PH and 3YSZ powders were 71.7 and 47.1 vol.%, respectively. Based on CPVC analysis, four feedstocks with optimal powder loadings of 69 and 70 vol.% for SS17- 4PH and 44 and 45 vol.% for 3YSZ were prepared. During the injection moulding process, SS17-4PH and 3YSZ feedstocks with powder loadings of 69 and 44 vol.%, respectively, were utilized to fabricate the green SS17-4PH/3YSZ micro-parts. Around 73.3% palm stearin was removed from the bi-material during the solvent debinding process. The open channels that developed in the solvent debound components helped to eliminate 96 to 99% of the binder in the thermal debinding stage. The density of the bi-material micro-parts after sintering reached 99% of the theoretical density. The sintered parts exhibited linear shrinkage between 9.3 ~ 17.4% in comparison to green parts. The microstructures from FESEM revealed the bonding between SS17-4PH and 3YSZ. EDS point and layered spectrum analysis displayed the existence of Fe, Ni, Cr, Zr, O, and Y at the interface that caused bonding as a consequence of the generation of the oxide layer in the process of co-sintering. The maximum hardness obtained along the bonding region of sintered bi-material micro-part was 1439.6 HV. Additionally, the tensile strength reached to 13.7 MPa. In conclusion, the findings exhibited that twomaterial SS17-4PH/3YSZ is successfully fabricated through 2C-μPIM process by overcoming the incompatibility in the physical and thermal properties of SS 17-4PH and 3YSZ materials.,Ph.D.
Pages:	200
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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