Hydroxyapatite coating on stainless steel 316L using investment casting technique

Decades of research had found that the use of hydroxyapatite (HA) could promote osseointegration and increase the mechanical stability and strength of the metallic implant. Currently, medical implants are produced by machining, metal forming and casting particularly investment casting technique. Comparatively, the investment casting technique is more practical to mass produced implant due to its simplicity, superior surface finish, relatively cheap process, capability to produce complex and near-net shape implants. Investment casting technique provides a single stage processing technique in producing coated implant i.e. HA coated on the cast implant. In this respect, the possibility of applying HA layer during casting for implant substrate using investment casting was explored. Previous studies used paint brush in applying HA layer onto the internal cavity of the ceramic mould. However, the layer thickness was inconsistence which affects the quality of the HA layer coated on the casting and impractical for small and complex shapes components. In this study, medical grade 316L stainless steel (316L-SS) was coated with HA using investment casting technique by pouring molten 316L-SS into a HA coated ceramic mould at temperature of 1650?C in argon gas. The coated samples were sintered in a furnace at four different temperatures (600, 800, 1000 and 1200?C) for 1 hour. The as-cast and sintered HA coated samples were characterised using scanning electron microscopy, energy dispersive x-ray spectroscopy and x-ray diffraction analysis. Results showed that the as-cast samples produced good HA coating bond, formed amorphous phases and complex calcium-chromium oxide (CaCrO) layer at the interface between HA and 316L-SS. Sintering process was conducted to recrystallise and improve the properties of the as-cast HA coating. The results confirmed that crystallinity and purity of the coating increased with increasing sintering temperature whilst Ca/P ratio and porosity decreased. Increasing sintering temperature from 600 to 800ºC did not significantly alter the crystallinity and purity. The crystallinity and purity recorded at that temperature range were 57.35% - 58.55% and 61.80% - 63.21% respectively. This temperature range was considered insufficient to recrystallise and purify the coating to an acceptable value for implant applications. Increased of sintering temperature from 1000 to 1200ºC increased the crystallinity from 73.52% - 74.47% and purity from 61.80% - 81.8%. Simultaneously, the Ca/P ratio and porosity were reduced to 1.51 and 14.14% respectively which is acceptable to human body. Sintered as-cast specimen at 1000ºC immersed into Simulated Body Fluid (SBF) solution showed increased in Ca/P ratio with increasing immersion time indicating that the coating was bioactive

Shell Mould Strength of Rice Husk Ash (RHA) and Bentonite Clays in Investment Casting

Investment casting process (IC) plays a major role in the modern manufacturing process in providing an economical means of mass production components with intricate shape and complex geometry as demand in various crucial applications including aerospace, automotive, military, biomedical and others. This casting technique, develop shell mould fabrication by coating the required pattern with a refractory mixture which offers the complex geometrical shape and sizes parts to be cast. However, the modern IC approach in shell mould production suffers from zircon’s cost and supply instability as it is the main material to be used. Zircon uses as refractory filler for slurry production, and also in the form of sand used as stucco particles, is favoured by the investment casting facilities and industries as it exhibits the most versatile properties such as low thermal expansion and low reactivity to the metal to be cast. During the period of zircon supply shortage, many facilities introduce several alternatives. Currently, the step taken to reduce the cost of primary slurry material is by using some alternate refractory material like, alumina, silica, to be used with zircon for shell mould production. In relation to that, several researches continue to search for alternatives approach for shell mould materials. This research introduces the alternative method in fabricating investment casting shell mould as recognized from investment casting industry located in Sungai Puar of Bukittingi Padang Indonesia. This industry employs several local resources to fabricate the shell mould. These materials consist of rice husk ash (RHA), and two types of bentonite clays. The bentonite clays were obtained nearly from Kota Payakumbuh in the western provinces. However, this industry suffers from weak shell mould strength and need to be investigated and consulted. In this paper, the investigation on shell mould strength made from rice husk ash (RHA), and bentonite clays were conducted. The strength was measured by its modulus of rupture (MOR) performed in 3 points flexural bending test. The green and fired shell mould strength was determined from five type of slurry composition. The results revealed that the highest green and fired strength obtained were 0.157 MPa and 0.361 MPa from shell mould sample C of RHA (46%) and bentonite (54%) of its composition

Piston ring assembly for a new natural gas vehicle symmetrical multistage wobble-plate compressor

Natural gas is an alternative fuel of choice in the market today due to the increase in the price of petroleum, as well as out of environmental concerns. Pressure requirement for a natural gas vehicle (NGV) storage tank is 3000 psig (206 bars). Thus, at NGV refueling facilities, the natural gas need to be stored at a higher pressure in order to refuel the NGV at the pressure required. Compressors are needed in the compression process at the refueling facilities. A new compressor design for natural gas refueling appliance has been developed which is the symmetrical multistage wobble-plate compressor. This compressor design is the newest variation of the axial reciprocating piston compressor. The success of the compressor design in compressing gas depends on the piston ring assembly design. Through this paper, the process of designing the piston ring assembly and considerations taken for this new compressor design were explained. The results presented are those from preliminary tests using air on the working fluid. Real tests on natural gas are to be organised utilising all the experience and lesson learnt from that on air

Microstructure analysis of hydroxyapatite coating on stainless steel 316L using investment casting technique for implant application

Osteoporosis and traffic accidents are a significant factor that causes a bone fracture in Indonesia. One solution for the bones fracture treatment is by using fixation implant that has similar characteristics with the human bones. Stainless Steel (SS) 316L is one of biomaterial that has been used as an implant material due to its corrosion resistance, excellent biocompatibility, and excellent mechanical properties. However, the bioactivity properties of the material are needed to improve by coating it with hydroxyapatite (HA). In this research, HA was coated to the surface of 316L SS by using investment casting technique. A slurry of HA was poured into the casting cavity surface prior to the metal casting process and then followed by sintering at temperatures of 850°C, 900°C, and 950°C. Characterization of HA coating layer on specimen surface was conducted by Optical Microscope, Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray (EDX). The hardness of the samples was measured by Vickers Hardness Tester. The result of the experiment shows that the investment casting is successfully to coat the HA on the SS 316L surface. Pouring method produces HA layer with thickness (spongy and porous surface) in the range of 60 μm - 110 μm. The increasing of sintering temperature increases the hardness number of the surfaces, and affect the purity of HA, but it is not related to coating thickness. The optimum sintering temperature is obtained at 900°C which produces the best calcium and phosphate ratio. The investment casting method is found as a simple and non-expensive technique that can be used to coat HA powder to SS 316L that produces good properties and optimum crystallinity of HA that suitable for orthopaedic implant application

Microstructure Analysis of Hydroxyapatite Coating on Stainless Steel 316L Using Investment Casting Technique for Implant Application

Osteoporosis and traffic accident are major factor that causes bone fracture in Indonesia. One of solution for the bones fracture treatment is by using fixation implant that has similar characteristics with the human bones. Stainless Steel (SS) 316L is one of biomaterial that has been used as an implant material due to its corrosion resistance, good biocompatibility, and excellent mechanical properties. However, the bioactivity properties of the material is needed to improve by coating it with hydroxyapatite (HA). In this research, HA was coated to the surface of 316L SS by using investment casting technique. A slurry of HA was poured into casting cavity surface prior to metal casting process, and then followed by sintering at temperatures of 850oC, 900oC, and 950oC. Characterization of HA coating layer on specimen surface was conducted by Optical Microscope, Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray (EDX). Hardness of  the samples was measured by Vickers Hardness Tester. Result of the experiment shows that the invvestment casting is successfully to coat the HA on the SS 316L surface. Pouring method produces HA layer with thickness (spongy and porous surface) in the range of 60 µm – 110 µm. The increasing of sintering temperature increases the hardness number of the surfaces, and affect the purity of HA, but it is not related to coating thickness. Optimum sintering temperature is obtained at 900oC which produces the best calcium and phosphate ratio. The investment casting method is found as a simple and non-expensive technique that can be used to coat HA powder to SS 316L that produces good properties and optimum crystallinity of HA that suitable for orthopedic implant application

SIMULASI DAN ANALISIS LOCKING COMPRESSION PLATE IMPLAN TULANG PAHA MENGGUNAKAN METODA FINITE ELEMENT ANALYSIS

Penggunaan implan pada kasus patah tulang (atau secara umum disebut pemasangan pen), bertujuan untuk menyangga atau menyambung bagian tulang yang patah. Implan ini secara ilmiah dinamakan Locking Compression Plate (LCP) yang terdiri dari pelat dan sekrup. Berdasarkan fungsinya sebagai penyambung, maka LCP dirancang untuk dapat menanggung beban tubuh dan beban lainnya sampai tulang itu sembuh dan menyatu kembali.  Namun, ada kasus tulang paha patah (femur fracture) yang telah disambung menggunakan LCP mengalami patah pada pelat sebelum tulang sembuh sehingga harus dilakukan kembali operasi kedua untuk pemasangan pelat yang baru. Penelitian ini bertujuan untuk membuktikan kekuatan bahan pelat LCP apakah patah akibat pembebanan yang melebihi kekuatan bahannya atau tidak. Rekonstruksi menggunakan software berbasis 3D Computer Aided Design (CAD) dengan metoda simulasi Finite Element Analysis (FEA). Beban yang diberikan tidak hanya secara vertikal mengikuti beban tubuh diatas tulang paha, namun juga dianalisis beban secara horizontal dan torsional. Disamping itu, juga dikembangkan rancangan pelat dalam 5 bentuk lainnya sebagai alternatif rancangan (prototipe). Hasil penelitian menunjukkan bahwa bahan pelat LCP yang digunakan adalah Stainless Steel 316L medical grade yang sesuai dengan standar bahan implan. Dengan adanya penelitian ini diharapkan dapat memberikan kontribusi desain dan informasi tentang penggunaan pelat LCP yang baik sehingga kasus-kasus yang mengalami pelat patah dapat dihindari

Effect of forging temperature on biodegradable MG-0.7%ca alloy properties for implant application

The potential of binary Mg-Ca alloy as biodegradable material is considerable interest in implant application among researchers. This research was conducted to investigate the effect of different forging temperature and forging speed on the hardness, microstructure and corrosion rate of Mg-0.7%Ca. The experiment was established by preparing the alloy sample with 0.7%wt calcium content. The forging process was carried out under four different temperature variations of 140°C, 180°C, 220°C, and 260°C ( 10°C) with two different speed;25 and 45 strokes per minute (spm). The samples microstructure was examined by optical microscope and scanning electron microscope (SEM) equipped with energy dispersive X-ray (EDX). The mechanical properties of the forged samples were measured in its hardness and plastic deformation ability along with samples cold-working percentage. The corrosion rate was determined by performing the electrochemical test in simulated body fluid. This research found that increases of forging temperature and forging speed provide a higher rate of recrystallization and Mg2Ca compound precipitation results in greater hardness, increase deformation and reduce the cold-working percentage. However, the investigated factors still led to a high corrosion rate compared to a previous study and consequently, reduce the feasibility of the alloy in implant application for biodegradable material

RANCANGAN PERAHU PELAT DATAR UNTUK KELOMPOK NELAYAN MUARO TANJUANG DANAU MANINJAU

Danau Maninjau merupakan salah satu danau yang terletak di Kabupaten Agam, provinsi Sumatera Barat. Danau ini mempunyai banyak potensi bagi masyarakat sekeliling danau dalam usaha kecil menengah. Salah satu aktifitas usahanya adalah nelayan Keramba Jaring Apung (KJA). Perahu adalah salah satu peralatan penting dalam transportasi nelayan baik itu untuk mencari ikan ataupun sarana transportasi dari pinggir danau ke penangkaran ikan di KJA  perancangan perahu pelat datar (PPD) metode penelitian yang  dilakukan dengan menelaah permasalahan material dan pembuatan perahu tradisonal. Proses Perancangan  PPD.Kegiatan pembuatan perahu pelat datar diawali dengan perancangan PPD. Proses perancangan dilaksanakan di Laboratorium Material Jurusan Teknik Mesin Fakultas Teknik Universitas Negeri Padang. Dalam proses perancangan PPD ini melalui beberapa tahapan diantaranya : Perancangan desain kapal, Penentuan tahanan perahu. Proses Pemotongan Pola pada Pelat.Dari desain yang telah di rancang terdapat 8 bagian pemotongan pola gambar, Proses Penyambungan Bagian Pelat, Proses Finishing. Desain alat disesuaikan dengan ukuran dimensi pada kapal tradisional. Pembuatan gambar detail perahu menggunakan Solidworks 2019, dan analisis numerik menggunakan software maxsurf. Pembuatan perahu pelat datar dengan bahan pelat besi sangat berpotensi sebagai alternative pembuatan perahu di sekitaran danau Maninjau. Penggunaan bahan perahu yang tanpa proses pembengkokan sangat efektif dan mudah dalam pengerjaan.