Mohd Afian Omar

Investigation of Rheological Behavior of Low Pressure Injection Molded Stainless Steel Feedstocks

The purpose of this research is to investigate the influence of different powder loadings of 316L stainless steel (SS) powders on rheological behavior of feedstocks required for low pressure powder injection molding (L-PIM) process. The main idea consists in development of various formulations by varying 316L SS powder contents in feedstocks and evaluating the temperature sensitivity of feedstock via flow behavior index and activation energy. For this purpose, the irregular shape, spherical shape, and combination of both shapes and sizes (bimodal approach) of 316L SS powders are compounded with wax based composite binder. Moreover, the influence of elemental nanosized boron (B) addition (up to 1.5 wt.%) on rheological properties of irregular shape 316L SS powders is also evaluated using capillary rheometer method. It is observed that rheological parameters for solid powder loading of powder gas atomized (PGA) and bimodal powder P25/75 316L SS underwent sudden change from PGA-69 vol.% to PGA-72 vol.% and P25/75-67 vol.% to P25/75 316L SS 70 vol.%, respectively. Thus it is concluded that PGA-69 vol.% and P25/75-67 vol.% are optimal powder solid loadings corresponding to the lowest values of activation energies.

Fabrication of Low-Cost, Cementless Femoral Stem 316L Stainless Steel Using Investment Casting Technique

Total hip arthroplasty is a flourishing orthopedic surgery, generating billions of dollars of revenue. The cost associated with the fabrication of implants has been increasing year by year, and this phenomenon has burdened the patient with extra charges. Consequently, this study will focus on designing an accurate implant via implementing the reverse engineering of three-dimensional morphological study based on a particular population. By using finite element analysis, this study will assist to predict the outcome and could become a useful tool for preclinical testing of newly designed implants. A prototype is then fabricated using 316L stainless steel by applying investment casting techniques that reduce manufacturing cost without jeopardizing implant quality. The finite element analysis showed that the maximum von Mises stress was 66.88 MPa proximally with a safety factor of 2.39 against endosteal fracture, and micromotion was 4.73 μm, which promotes osseointegration. This method offers a fabrication process of cementless femoral stems with lower cost, subsequently helping patients, particularly those from nondeveloped countries.

Interaction between Binder and Powder in Injection Moulding of 316L Stainless Steel

Owing to several steps involved in metal injection moulding (MIM) process, it is important to understand the interactions between metal powder and binder mixture particularly during mixing, injection moulding and debinding. A polar organic compound generally forms hydrogen bonds more readily with metal powder because of acid-base interactions. In this study, the interaction of local binder system comprised of; palm stearin (PS) and thermoplastic natural rubber (TPNR) with conventional binder; polyethylene (PE), polypropylene (PP) and paraffin wax (PW) and mixed with 316L stainless steel powder were investigated. The results showed that all the binder have high interaction with 316L stainless steel that make, the resulting the bonding sufficiently strong and suitable for MIM process. Keywords: Chemical interaction, Injection Moulding, Binder, Rheology

Effects of Residual Carbon on Microstructure and Surface Roughness of PIM 316L Stainless Steel

Powder injection molding (PIM) offers an attractive method for producing smart and intricate shapes components. PIM process is cost effective and equally applicable for metals and ceramics. Debinding process is the most critical step among all PIM steps and any residual during debinding can change the composition of sintered product resulting change in final properties. In this research work, the injection molded samples were thermally debound and sintered in various atmospheres. The results showed that the sintered samples with improper thermal debinding resulted the carbide formation at the surface and across the grain boundaries that caused to increase the roughness value.

Sintering Characteristics of Injection Moulded 316L Component Using Palm-Based Biopolymer Binder

Metal injection moulding (MIM) has been widely recognised as an advanced technology for the fabrication of complex-shaped, low cost and high performance components. Fine powders, less than 20 micron in diameter, are mixed with suitable thermoplastic binder and formed into the desired shapes. The binder aids the flowability and formability of fine metal powders during moulding, and they have to be removed in the next stage to enable high density components to be produced. The removal of the binder is done either thermally in the furnace or by solvent extraction. Ideally, the removal of the binder would open up pore channels which allow accelerated removal of the higher boiling point components. The components are sintered following the debinding stage. This stage is crucial to the MIM process as appropriate sintering conditions would ensure pore-free structures that have good mechanical properties (German, 1990; German and Bose, 1997)

Tribological Properties of 316L Stainless Steel Fabricated via Metal Injection Molding

The tribological properties of sintered 316L stainless steel fabricated via injection molding were investigated. Tests were carried out at room temperature comparing metal injection molded dog bone tensile samples at different sintering temperatures. The parameter used for the pin on disk test is a 10kN load, 500m sliding distance and a chromium steel ball as a sliding partner. The morphologies and compositions of the worn surfaces were analyzed by SEM, Raman and XPS. The results showed that the wear mechanism and friction coefficient of SS316L depended strongly on the microstructure which was influenced by the sintering temperature.

Rapid Debinding of Injection Moulded M2 High Speed Steel Using Palm Stearin/Waste Rubber Binder

Tendency of injection moulded parts to necessitate a long debinding time which consequently leads to an increase of defects formation has been a major obstacle for the economic process of Metal Injection Moulding (MIM). In the present study, a novel binder system based on waste rubber has been formulated in injection moulding of Molybdenum High Speed Steel (M2 HSS). The feedstock consisted of M2 HSS powder with mean diameter particle size of 16μm and binder which comprised of palm stearin, polyethylene, waste rubber and stearic acid. The moulded part was immersed into n-heptane at 60°C in order to remove the palm stearin and stearic acid, followed by sintering in a controlled vacuum atmosphere. Results showed that solvent extraction debinding technique allowed complete removal of palm stearin and stearic acid from the injection moulded part within 3 hours without swelling or distortion of the debound part. In addition, this study has demonstrated that, the novel binder system has successfully shorten the debinding time through a single stage debinding process whilst the sintered part possessed approximate density of 8.1 g/cm3 and hardness of 76.9 HRC.

Innovative Metal Injection Molding (MIM) Method for Producing CoCrMo Alloy Metallic Prosthesis for Orthopedic Applications

Powder injection molding (PIM) is a powder metallurgy process currently used for the production of complicated and near net shape parts of high performance materials [. This technique basically combines the advantages of plastic injection molding and the versatility of the conventional powder metallurgy technique. The process overcomes the shape limitation of powder compaction, the cost of machining, the productivity limits of isostatic pressing and slip casting, and the defect and tolerance limitations of conventional casting [1, 2, . According to German and Bose [, the technology of metal injection molding (MIM) is more complicated than that of the plastic injection molding, which arises from the need to remove the binder and to densify and strengthen the part. The process composed of four sequential steps: mixing of the powder and organic binder, injection molding, debinding where all binders are removed and sintering [1, 2, 3, 4]. If it necessary, secondary operations such as heat treatments after sintering can be performed [1, 2, 3, 4, .

Development of Metal Injection Moulding Process for Medical Applications

To counter the problems associated with the conventional processes of producing implants, a new approach has been invented, which is the adaptation of the injection moulding process for manufacturing the fracture fixation plates. With this technique in place, we have now taken a step in the right direction towards rapid manufacturing of fracture fixation plates, for the first time. The fracture fixation plates produced using this technique comply with the international standards including MPIF Standard 35, ISO 5832-1 and ISO 10933. The advantages of the present invention are design flexibility, rapid manufacturing, cost effectiveness and minimal waste compared to conventional process

Single Step of Binder Thermal Debinding and Sintering of Injection Moulded 316L Stainless Steel

Metal injection moulding was performed with gas atomized 316L stainless steel powders. Feedstocks were prepared using a paraffin wax/polyethylene/stearic acid binder system and subsequently molded into tensile bar specimens. Solvent extraction done at 80○C has shortened the debinding process to 30 minute. Single step of thermal binder debinding and sintering was done in a vacuum furnace. Sintering at 1380○C has reduced the porosity and associated with grain growth that result in an increase in ultimate tensile strength to 444 MPa while the elongation increased to 29% before fracture.