CHARACTERISATION OF STAINLESS STEEL 316L AND PALM STEARIN BASED BINDER BY USING METAL INJECTION MOLDING (MIM) PROCESS

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1 CHARACTERISATION OF STAINLESS STEEL 316L AND PALM STEARIN BASED BINDER BY USING METAL INJECTION MOLDING (MIM) PROCESS MURNI FARAHIN BT MUSA ZAINAL ABIDIN A thesis submitted in fulfilment of the requirements for the award of the degree of Master of Engineering (Materials Engineering) Faculty of Mechanical Engineering Universiti Teknologi Malaysia JUNE 2014

2 iii Thank you Allah and a special thanks is dedicated to my beloved parents for supporting me through my master program in UTM. Without their bless and support, I could not have smooth and ease in all my way through here. Zillion thanks to my supervisor for guiding me through this project. Without her guidance and supervision, I will not finish this project on track. I also will not manage to succeed here without moral support and bunch of help from my dear friends. They are very helpful when I really need help. Thank you for all the supports that you have shown. I really appreciate all the helps.

3 iv ACKNOWLEDGEMENT In preparing this thesis, I was in contact with many people, researchers and academicians. They have give huge contribution towards my understanding of this project and machines that I should use. In particular, I wish to express my sincere appreciation to my main thesis supervisor, Dr. Norhayati bt Ahmad, for encouragement, guidance, advices, motivation, critics and friendship. I am also very thankful to Dr. Khairur Rijal for letting me use his machines, Metal Injection Molding machine and Vacuum Furnace which available at UTM Jalan Semarak, KL. He also helps me in understanding the Metal Injection Molding process and defects. Without his approval and support, this project could not finished and presented in the same way as I presented here. I am also want to thank Universiti Kebangsaan Malaysia (UKM) for giving me a chance to use material engineering department s laboratory. They deserve a special thanks for the support and cooperation that we had went through. I am very grateful to all my family members as well for their endless moral and physical support towards me here. My fellow postgraduate students should also be recognized for their support. My sincere appreciation also extends to all my colleagues and others who have provided assistance at various situations. Their thoughts and recommendation are very useful indeed. Unfortunately, I am not possible to list down all of their names here due to limited space.

4 iv ABSTRAK Polisterin telah menjadi isu degradasi sekian lama kerana ia tidak boleh terurai secara semulajadi. Dalam projek ini. Polisterin (PS) yang telah dikitar semula telah dijadikan sebagai pengikat utama dalam pengacuan suntikan logam (MIM). Objektif projek ini ialah untuk menyiasat parameter suntikan optimum untuk keluli tahan karat 316L dengan pengikat polimer (PS, PE, stearin sawit dan gliserol) dan kajian ciri kekerasan dan keliangan juga mikrostruktur selepas acuan suntikan. Bahan suapan 63wt%, 64wt% dan 65wt% dihasilkan daripada proses pencampuran. Kesemua sebuk mentah disuntik dengan parameter suntikan yang telah dimanipulasi bagi suhu acuan dan tekanan untuk mencari parameter yang optimum yang boleh menghasilkan bentuk dumb bell yang sempurna. Parameter suntikan ( suhu acuan: 110 hingga 115 o C dan tekanan : 7 hingga 8kPa) boleh menghasilkan bentuk dumb bell yang sempurna diteruskan dengan proses penyahikatan, proses pensinteran, ujian mekanikal dan analisa. Daripada kajian, bahan suapan 63wt% menunjukkan pengaliran dan pembentukan yang bagus serta tahap ketahanan tinggi (388Hv) selain tahap keliangan yang rendah (89%) apabila menggunakan 110 o C sebagai suhu acuan dan tekanan sebanyak 7kPa.

5 v ABSTRACT Polystyrene (PS) has been a nature s degradable issue as it cannot biodegradable. In this project, recycle polystyrene (PS) is used as main binder in Metal Injection Molding (MIM). The research aims are to investigate the optimum injection parameter for stainless steel 316L with polymeric binder (PS,PE, palm stearin and glycerol) and study its hardness and porosity also microstructure after injection molding. 63wt%, 64wt% and 65wt% of powder loading of feedstock were prepared in mixing process. All prepared feedstock were injected under manipulated injection parameter for mold temperature and pressure to find the optimum parameter which can inject full dumb bell shape. The injection parameter (mold temperature: 110 to 115 o C and pressure: 7 to 8kPa) which able to produce full dumb bell shape is continued for debinding process, thermal pyrolisis process, sintering process, mechanical testing and analysis. From the studies, 63wt% of powder loading shows good flowability and moldability with high hardness (388Hv) and low porosity (89%) when using 110 o C as mold temperature and 7kPa of pressure.

6 vii TABLE OF CONTENTS CHAPTER TITLE PAGE DECLARATION DEDICATION ACKNOWLEDGEMENT ABSTRACT ABSTRAK TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF APPENDICES ii iii iv v vi vii x xii xiv 1 INTRODUCTION Significant And Benefits Of Research Objectives Problem Statement Scope Of Work 4 2 LITERATURE REVIEW Precision Manufacturing of Medical Device Metal Injection Molding (MIM) Mixing Injection Binder Removal or Debinding Process 14 15

7 viii Sintering Process Stainless Steel as Powder Material Stainless Steel as Orthopedic Implant Corrosion of Stainless Steel 316L in Human Body Polystyrene as Binder Polyethylene Palm Stearin Research of Metal Injection Molding MPIF Standard RESEARCH METHODOLOGY Mixing Process Injection Molding Process Debinding Process Sintering Process Mechanical Testing Hardness Test Microstructure Study 3.7 Fourier Transform Infrared Analysis (FTIR) RESULTS AND ANALYSIS 4.0 Introduction Fourier Transform Infra Red (FTIR) Spectroscopy 46 Analysis. 4.2 Hardness Test Porosity Test 63 5 CONCLUSION AND RECOMMENDATION Conclusion Future Work 66

8 ix REFERENCES APPENDICES 67 69

9 x LIST OF TABLE TABLE NO. TITLE PAGE Table 2.1 Table 2.2 Table 2.3 Table 2.4 Table 2.5 Table 3.1 Table 3.2 Table 4.1 Table 4.2 Table 4.3 Table 4.4 Comparison between Metal Injection Molding (MIM) and Powder Compaction. Major biomedical metals and alloys and their applications. Content of palm stearin with its melting point. Chemical composition of MIM materials. Mechanical properties of stainless steel in MIM materials properties. Injection parameters which are manipulated in this research at all stages of each series of experiments. Injection molding parameters which are maintained for 63%, 64% and 65wt% powder loading. Preliminary result of Metal Injection Molding (MIM) for 63, 64, 65wt% powder loading. Result for sintered sample of MIM after hardness testing. Result of mechanical testing for sintered sample using pressure of 8kPa in MIM parameter. Result of brown part when it is injected using 115 o C for mold temperature and 7kPa in pressure for MIM parameter

10 xi LIST OF FIGURE FIGURE NO. TITLE PAGE Figure 2.1 Gear and screw produce with MIM. 10 Figure 2.2 Fasteners made from MIM. 11 Figure 2.3 MIM components with no geometric shape restriction. 12 Figure 2.4 Picture of part after sintering on left side and right side is product before sintering and after debinding process. 16 Figure 2.5 Knee and hip implant from metal alloy. 18 Figure 2.6 Products made from palm stearin. 22 Figure 3.1 Brabender machine for mixing process. 30 Figure 3.2 Mixing process is done at this part of Brabender machine. 30 Figure 3.3 Mixing chamber. 31 Figure 3.4 Crushing machine. 31 Figure 3.5 Crushing process is done at this chamber. 32 Figure 3.6 Micro Injection Molding (MIM) machine. 32 Figure 3.7 Figure 3.8 Injection barrier where feedstock is inserted and melted in it. Injection molding apparatus to clean the barrier and removed mould from injection molding machine Figure 3.9 Venticell Furnace. 36 Figure 3.10 Figure 3.11 Example of green specimen immersed in n-heptane solution. Green specimen is placed inside the furnace for debinding process

11 xii Figure 3.12 Low Vacuum Furnace. 38 Figure 3.13 Shimadzu Micro Hardness. 39 Figure 3.14 Figure 3.15 Figure 3.16 Figure 3.17 Schematic diagram about diamond indenter touches on the surface of a specimen. Formula for hardness test using Viskers Hardness Tester. Scanning Electron Microscope (SEM) which is available at Universiti Teknologi Malaysia (UTM). Tabletop SEM available at FBME. Images were taken here when SEM at FKM was broken Figure 3.18 Diagram of how FTIR works to produce wavelength. 44 Figure 3.19 Figure 4.1 FTIR Spectrometer machine which is available at Faculty of Chemical Engineering is used to identify polymeric binder. FTIR of palm oil and sesame oil. FTIR or palm oil is a reference for this research Figure 4.2 FTIR spectrum for polystyrene. 48 Figure 4.3 FTIR spectrum for polyethylene. 48 Figure 4.4 FTIR spectrum for glycerol. 49 Figure 4.5 FTIR spectroscopy analysis of palm oil (PO), polystyrene (PS), polyethylene (PE) and glycerol (glc). 50 Figure 4.6 Figure 4.7 Figure 4.8 Figure 4.9 FTIR spectroscopy shown above is taken for sintered sample. From FTIR analysis, glycerol (glc) and palm oil (PO) are present in the analysis. Metal content in white colour images from EDX result obtained Microstructure of 63wt% under 110 C for mold temperature, 180 C for melt temperature and 7kPa in pressure. Microstructure of 64wt% under 110 C for mold temperature, 180 C for melt temperature and 7kPa in pressure

12 xiii Figure 4.10 Figure 4.11 Figure 4.12 Figure 4.13 Figure 4.14 Figure 4.15 Figure 4.16 Figure 4.17 Figure 4.18 Figure 4.19 Figure 4.20 Microstructure of 65wt% under 110 C for mold temperature, 180 C for melt temperature and 7kPa in pressure. Microstructure of 63wt% under 110 C for mold temperature, 180 C for melt temperature and 8kPa in pressure. Microstructure of 64wt% under 110 C for mold temperature, 180 C for melt temperature and 8kPa in pressure. Microstructure of 65wt% under 110 C for mold temperature, 180 C for melt temperature and 8kPa in pressure. Microstructure of 63wt% under 115 C for mold temperature, 180 C for melt temperature and 7kPa in pressure. Microstructure of 64wt% under 115 C for mold temperature, 180 C for melt temperature and 7kPa in pressure. Microstructure of 65wt% under 115 C for mold temperature, 180 C for melt temperature and 7kPa in pressure. Hardness obtained from experiment using 110 o C and 115 o C mold temperature and 7kPa pressure in MIM parameter. Comparison of hardness value using 7kPa and 8kPa in pressure and 110 o C for mold temperature. Percentage of porosity in sintered part of 110 o C and 115 o C in mold temperature using 7kPa pressure were compared. Percentage of porosity for sintered part after injected with 7kPa and 8kPa in pressure

13 xiv LIST OF APPENDICES APPENDIX TITLE PAGE A Gant Chart I 64 B Gant Chart II 65

14 CHAPTER Introduction Metalworking industries has been growing up since then and metalworkers started to learn and implemented better quality product from metal alloys such as wrought iron, cast iron and steels. From this implementation, people started to develop more products form iron and metal alloys and trigger Industry Revolution where boilers, steam engines and railways can be made from mass production. As for today, many products are being made in metal from advance metal alloy. The techniques of fabricating the metals are also facing a revolution. The revolution in technique of fabricating metal has introduced Metal Injection Molding (MIM). By using this technique precise and intricate product from big to nano-scale size product can be made. This technique often used in electronic industry. This process is similarly like baking a cake. MIM is a process of manufacturing where combination of metal powder and binder can produce a very precise, optimum mechanical properties and intricate shape product. Binders used in this process can be organic and inorganic product. For an instance, recycle polymer product can be implemented and use as binder since it is hard to degrade naturally in earth besides it creates hazardous gas when polymer degrades naturally with other items. The resource of recycle polymer can be found in mineral water bottle, beads of pillow, shampoo bottle and even toys (Rashid,2011). When metal powder and binders are mixed in mixing machine, it creates a mixture of feedstock (Rashid and Amalina,2011). Feedstock has to be transformed into granulate shape in order to melt it in injection molding for shaping into desired

15 2 shape product. At this stage, feedstock is heated and melted at polymer melting point then injected in the mould. After injection process, the desired part is allowed to cool to a solid form. In order to obtain the metal part, part which also known as green part has to undergo debinding process. In this process, low melting point binder is removed and the remaining part is sintered to ensure binder is completely removed from metal part in sintering process. Low melting point binder in this binder system is palm stearin. Palm stearin will be removed from the specimen through debinding process. Other binders are removed via sintering process which requires more heat. 1.1 Significant and Benefits of Research MIM process is a new approach in Malaysia. By applying MIM in Malaysia, many profits can be gained and new gadgets can be produced without dependency on import product. Malaysia has high potential in MIM industry as the material for binder and powder metal can be obtained in Malaysia. Binder for MIM can adapt a wide range of materials because MIM can be used for high temperature in melting temperature. Local binder of MIM is beneficial to industry and has become a great concern in research. Binder system of MIM has been varied and attempted in research in order to find the most cost reduction and can shorten production process. Polystyrene has been used for food container in 1990s. Polystyrene has become a favorable food container among the businessman especially in food industry because of hygiene factor where the food is resisted from bacteria growth and water from entering the food. Polystyrene has been made for other various products such as solid spoons and folks, polystyrene cups and plates and disposable polystyrene razor. Polystyrene has attracted many industries as its light weight, economical and sturdy which against moisture but at the same time maintain its original shape. Polystyrene has become a critical issue in Malaysia where it can be biodegradable. Polystyrene can only degrade after 500 years in earth and resistance

16 3 to photolysis as reported by Amruta (2013). Polystyrene has been introduced as potential main binder in MIM. The character of can be burnt and vanished in air has captured researchers to try polystyrene as binder in MIM. Palm oil has become one of the largest exports in Malaysia. In 2007, palm oil industry has obtained RM 31.8 billion. Fractions of palm oil are majority of palm stearin and palm olein as reported by Siew Lin (2007). As in palm stearin, there are many fatty acids which can be used as lubricant and surfactant in MIM s binder system. One of fatty acids in palm stearin is stearic acid which is commonly used in MIM binder system as lubricant. Besides its high melting point which is in range of 44 to 56 ºC higher than room temperature, palm stearin is categorized as potential lubricant and surfactant for MIM s binder system. Palm stearin is also economical in price and easy to obtain in Malaysia rather than other foreign country. The most unique characteristic of palm stearin is that chemistry composition of palm stearin can be modified to meet the requirement of MIM. 1.2 Objective of Research The main objective in this research is to investigate the optimum metal injection parameter for the prepared feedstock which are 63wt%, 64wt% and 65wt% of powder loading. Another objective is to study the sintered specimen in hardness and porosity in order to find the best injection parameter. 1.3 Problem Statement Polystyrene (PS) and polyethylene (PE) have environmental problem in biodegradable. PS and PE are introduced as binder in MIM in order to overcome this problem as these polymers are classified as thermoplastic. PS and PE can be burnt and vanished in the air.

17 4 1. No study in optimum metal injection molding parameter (mold temperature, injection holding time, melting temperature and injection pressure) has been done for stainless steel 316L for particle size of 7.157µm. 2. Optimum powder loading composition of 63wt%, 64wt% and 65wt%. is not found yet for stainless steel 316L with powder particle of 7.157µm and powder loading of 63% and 64%. 1.4 Scope of Work The scope of this research is to investigate the optimum powder loading and binder composition for stainless steel 316L by using MIM process. 1. Preparation of feedstock with different solid loading (63wt%, 64wt% and 65wt%) mixed with polymeric binder by using Metal Injection Molding (MIM). 2. The green part was injected with different injection molding parameter to find optimum MIM parameter for each powder loading. The manipulated injection parameters were mold temperature (110 to 115ºC) and injection pressure (7 to 8 bar). Optimum parameter value of mold temperature and injection pressure will inject full dumb bell part with good mechanical properties. 3. The sintered part was injected with manipulated injection molding parameter was related with its hardness property.

18 62 REFERENCE Amalina Amir, March 2011, Development of Metal Injection Molding (MIM) Binder Formulation of 17-4PH Stainless Steel Powder, Master, UiTM Amruta Deshpande, 2013, Polystyrene Properties, Unpublished Note, Buzzle Bertazzo, S.; Gentleman, E.; Cloyd, K. L.; Chester, A. H.; Yacoub, M. H. Stevens, M. M., 2013, Nano-Analytical Electron Microscopy Reveals Fundamental Insights Into Human Cardiovascular Tissue Calcification,12 (6): , Nature Materials. Douglas C. Hansen, 2008, Metal Corrotion In Human Body : The Ultimate Bio- Corrosion Scenario, Vol. 17 No.2, The Electrochemical Society Interface. Dr Frank Petzoldt, 2007, Metal Injection Molding in Europe, Vol.1 No. 2, pages 23-28, PIM International Inovar Communications Ltd. Fei Ling Pua et. el, 2013, Solvolytic Liquefaction of Oil Palm Empty Fruit Bunch (EFB) Fibres: Analysis of Product Fractions Using FTIR and Pyrolysis- GCMS,42(6)(2013): , Sains Malaysiana. Hj Nor Rashid Ismail, 2010, The Green Choice Changing The Buying Habit of Malaysian Consumer, SIRIM Link Driving Innovation Through Technology, PP 10002/05/2010(024916), Page Jmazunder, 2014, White Paper Title: Precision Additive Manufacturing of Medical Device, The Pom Group, Inc. Juan M Adames, December 2007, Characterization Of Polymeric Binders For Metal Injection Molding (MIM) Process, Doctor of Philosophy, University of Akron. M. A. Omar, I. Subuki, N. S. Abdullah, N. Mohd Zainon and N. Roslani, 2012, Processing of Water-atomised 316L Stainless Steel Powder Using Metal-injection Processes, Vol. 8, MPIF Standard 35, 2007, Materials Standard for Metal Injection Molded Parts, New Jersey, USA, Metal Powder Industries Federation

19 63 National Institute of Standard and Technology (NIST), 2011, Glycerin, U.S, Coblentz Society Collection (C). NICODOM IR Suspect powders, 2013, Overview of Polystyrene, Unpublished Note, NICODOM Ltd. Nor Hafiez Mohamad Nor, Norhamidi Muhamad, Sri Yulis M. Amin, Sufizar Ahmad, Mohd Halim Irwan Ibrahim, Murtadhahadi, Khairur Rijal Jamaludin, 2008, Pengacuan Suntikan Logam (MIM) Bagi Serbuk Titanium Dengan Sistem Bahan Pengikat Stearin Sawit, Seminar I - AMReG 0, 12 Jun 2008, Seremban, Malaysia, Page 1-9. R. Ibrahim, M A Omar, W C Goh, M Mohamad, S Muhamad, N A Yahya, Z Radzi, N H Abu Kasim, 2007, Fabrication of 316L stainless steel parts by Injection Moulding for Biomedical Application using a Novel Binder, Biomed 06, IFMBE Proceedings 15, pp R. Ibrahim, M. Azmirruddin, M. Jabir, M.R. Ismail, M. Muhamad, R. Awang and S. Muhamad, 2010, Injection Molding of Titanium Alloy Implant For Biomedical Application Using Novel Binder System Based on Palm Oil Derivatives, ISSN , pp R.M. German, 1990, Powder Injection Molding, Princeton,New York, Metal Powder Industries Federation. Smith Metal Product, 2011, A Design Guide For MIM : Metal Injection Molding, Randall M. German,Metal Injection Molding A Comprehensive MIM Design Guide,1-58, Princeton, New Jersey, Metal Powder Industries Federation. Thermo Nicolet, 2001, Introduction to Fourier Transform Infrared Spectrometry, Thermo Nicolet Booklet, Brochure, Madison,U.S.A, Thermo Nicolet Coperation. Tsc, 2014, Hardness Test, Unpublished Note, Gordon England. Williams,B., 1989, Parmatech Shapes Metals like Plastics, Metal Powder Report, Vol. 44No.10, p