Pemilihan Bahan Suapan bagi Proses Pengacuan Suntikan Logam Berdasarkan kepada Kajian Sifat Reologi
Authors: Muhamad Norhamidi , Jamaludin Khairur Rijal , M. Amin Sri Yulis , Ab. Rahman Mohd Nizam 
Published: January 2013

Sifat reologi bahan suapan acuan suntikan logam MIM yang disediakan dengan keluli tahan karat 316L pengabusan gas dan, polymethyl methacrylate (PMMA), polietelena glikol (PEG) dan asid sterik sebagai bahan pengikat telah dikaji. Dai kapilari L/D = 10 telah digunakan dalam kajian ini. Serbuk keluli tahan karat kasar dan halus telah diadunkan dengan bahan pengikat pada beban serbuk 64% dan 65% isipadu. Kesemua bahan suapan mempamerkan tingkahlaku pseudo plastik memandangkan indek tingkahlaku alirannya kurang daripada 1, tetapi indek tersebut berkadar songsang terhadap beban serbuk. Seterusnya, indek tingkahlaku bagi serbuk kasar didapati lebih besar berbanding serbuk halus. Bahan suapan 16_64 lebih peka berbanding bahan suapan yang lain, dan bahan suapan 31_65 pula didapati kurang peka terhadap suhu dan tekanan. Bagaimanapun, kepekaan juga didapati berkadar songsang terhadap beban serbuk. Maka, indek kebolehacuan bagi 31_64 adalah yang terbaik, dan hasil kajian mendapati bahawa beban serbuk 64% isipadu menghasilkan kebolehacuan bahan suapan yang lebih baik. Akhirnya, kajian ini menyimpulkan bahawa kesemua bahan suapan sesuai untuk disuntik ke dalam acuan kerana sifat reologinya menunjukkan penipisan ricih apabila tegasan ricih dikenakan terhadapnya. Bagaimanapun, bahan suapan pada beban serbuk 64% isipadu adalah yang lebih sesuai disebabkan oleh indek kebolehacuan yang lebih tinggi daripada 65% isipadu.

Kata kunci: Pengacuan suntikan logam, reologi, indek tingkahlaku aliran, tenaga pengaktifan, indek kebolehacuan

Rheological properties of the metal injection molding (MIM) feedstock prepared with gas atomized 316L stainless steel and, polymethyl methacrylate (PMMA), polyethylene glycol (PEG) and stearic acid as binder have been investigated. Capillary rheometer with die of L/D = 10 was used in the investigation. Coarse and fine stainless steel powders were mixed with binders at powder loading of 64% and 65% volume. All feedstocks exhibit pseudo plastics behaviour as the flow behaviour indexes were less than one, but it is inversely proportional to the powder loading. Moreover, the flow behaviour index of the coarse powder is larger than the fine powder particles. Feedstock 16_64 exhibits higher sensitivity among other feedstocks while 31_65 was least sensitive to the temperature and pressure. However, the sensitivity was also inversely proportional to the powder loading. Thus, moldability index of the 31_64 is the best and result shows that powder loading 64% volume gives better moldability to the feedstocks. Finally, the investigation concluded that the feedstocks are suitable to be injection molded because the rheological properties demonstrate a shear thinning when subjected to shear stress. However, feedstock with the powder loading of 64% volume is the most suitable as the moldability index is higher than the 65% volume feedstocks.

Key words: Metal injection molding, rheology, flow behaviour index, activation energy, moldability index