The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform

C.j Choi - One of the best experts on this subject based on the ideXlab platform.

  • binder system for sts 316 nanopowder feedstocks in micro metal injection molding
    Journal of Materials Processing Technology, 2007
    Co-Authors: Sugeng Supriadi, Eung Ryul Baek, C.j Choi
    Abstract:

    Abstract The stainless steel (STS) 316 nanopowder (average Particle size of 100 nm) were mixed with thermoplastic binder system to produce feedstock for micro-metal injection molding (μMIM) by using lost mold method. The combination of paraffin waxes, bee's waxes, carnauba waxes, ethylene vinyl acetate (EVA), polypropylene (PP) and stearic acid were chosen as binder systems with various formulations adopted to attain optimum feedstock properties. Three different kinds of binder systems of EVA-based, PP-based, and wax-based binder system were deeply investigated. It is found that the wax-based binder system performs the lowest viscosity and heat capacity as well as greater pseudo-plasticity than other binder systems. The feedstocks were injected into SU-8 micromold which was fabricated using photolithography technique. The feedstock which was mixed with wax-based binder system performed the smallest deformation. This result inferred that wax-based binder system is appropriate as binder materials for very fine metal powder applied in μMIM. In this paper we also demonstrated the application of nanopowder on sintering process and showed that the Sintered Part using nanopowder provides less surface roughness than one produced using micron-sized metal powder.

  • binder system for sts 316 nanopowder feedstocks in micro metal injection molding
    Journal of Materials Processing Technology, 2007
    Co-Authors: Sugeng Supriadi, Eung Ryul Baek, C.j Choi
    Abstract:

    Abstract The stainless steel (STS) 316 nanopowder (average Particle size of 100 nm) were mixed with thermoplastic binder system to produce feedstock for micro-metal injection molding (μMIM) by using lost mold method. The combination of paraffin waxes, bee's waxes, carnauba waxes, ethylene vinyl acetate (EVA), polypropylene (PP) and stearic acid were chosen as binder systems with various formulations adopted to attain optimum feedstock properties. Three different kinds of binder systems of EVA-based, PP-based, and wax-based binder system were deeply investigated. It is found that the wax-based binder system performs the lowest viscosity and heat capacity as well as greater pseudo-plasticity than other binder systems. The feedstocks were injected into SU-8 micromold which was fabricated using photolithography technique. The feedstock which was mixed with wax-based binder system performed the smallest deformation. This result inferred that wax-based binder system is appropriate as binder materials for very fine metal powder applied in μMIM. In this paper we also demonstrated the application of nanopowder on sintering process and showed that the Sintered Part using nanopowder provides less surface roughness than one produced using micron-sized metal powder.

Hafizawati Zakaria - One of the best experts on this subject based on the ideXlab platform.

  • yttria stabilized zirconia formed by micro ceramic injection molding rheological properties and debinding effects on the Sintered Part
    Ceramics International, 2013
    Co-Authors: Farhana Mohd Foudzi, Abu Bakar Sulong, Norhamidi Muhamad, Hafizawati Zakaria
    Abstract:

    Abstract Micro Ceramic Injection Molding (μCIM) is a near net-shape process to produce smaller and intricate Parts at a competitive cost. The application of nano-sized ceramic powder in μCIM has the advantages of fine grain size growth and good surface finish. However, the nano size effect causes agglomeration and low powder loadings, which result in defects during the μCIM process and in the Sintered components. This study extensively investigated the debinding and sintering of yttria-stabilized zirconia (YSZ), as well as its rheological properties, using polypropylene (PP) as the primary binder and palm stearin as the secondary binder. 50 nm Yttria stabilized zirconia (YSZ) powders were mixed with palm stearin and PP at a powder loading of 37–43 vol%. The results of rheological studies showed that the feedstock had a dilatant flow characteristic and a viscosity of around 10–40 Pa s. Feedstock with 38 vol% powder loading had the lowest activation energy of 9.48 kJ/mol. The green Part of the injected feedstock had flexural strength ranging from 13 to16 MPa, within which the feedstock with 43 vol% powder loading had the highest green density. Solvent debinding was carried out at three temperatures (50, 60, and 70 °C) using heptane. A large porous region was clearly identified at 70 °C compared with 50 °C. A debinding split furnace with argon gas was used to remove PP at 450 °C for 4 h. The debound samples did not shrink when 94%–98% of the binder system was removed. All debound samples Sintered at 1350 °C and 41 vol% had the highest mechanical properties with hardness of 900 HV and a flexural strength of 400 MPa.

Javad Rajabi - One of the best experts on this subject based on the ideXlab platform.

  • effects of binder system and processing parameters on formability of porous ti ha composite through powder injection molding
    Materials & Design, 2015
    Co-Authors: Muhammad Rafi Raza, Javad Rajabi, Majid Niaz Akhtar, Abu Bakar Sulong, Norhamidi Muhamad
    Abstract:

    Abstract Porous titanium-hydroxyapatite (Ti/HA) composite is a developed composite material suitable for bio-medical applications. Powder injection molding (PIM) with space holder method is used to produce porous Ti/HA with mechanical properties, similar to human bone, and pores helps to initiate tissue growth. However, the differences in physical and mechanical properties of these composites are the main challenges during debinding and sintering. Therefore, the main objective is to determine effects of binder systems and processing parameters on formability of Ti/HA composite. In PIM, a binder system is necessary to produce green and ultimately Sintered Part. There are two binder systems and variation of sintering temperature has been used. Results revealed that Polyethylene glycol (PEG)-based binder system is applicable with NaCl space holder and optimum sintering parameters, including temperature, heating rate, and holding time of 1300 °C, 10 °C/min, and 5 h, respectively. The fabricated porous Ti/HA exhibits average porosity, pore size distribution, compressive strength, and roughness values of 55%, 60 μm to 170 μm, 370 MPa, and 0.323 μm, respectively. FESEM results showed that the pores are interconnected. It may be an appropriate material for future bio-medical applications.

Aibing Yu - One of the best experts on this subject based on the ideXlab platform.

  • three dimensional mpfem modelling on isostatic pressing and solid phase sintering of tungsten powders
    Powder Technology, 2019
    Co-Authors: Xizhong An, Aibing Yu
    Abstract:

    Abstract Particulate scale three-dimensional CIP and solid phase sintering of tungsten powder in powder metallurgy process was numerically reproduced using MPFEM method. The effects of initial packing structures on the densification behavior of the tungsten powders during CIP and sintering were systematically investigated. Various macroscopic and microscopic properties including relative density, overall/local stress distributions, deformation status, pore filling behavior as well as densification mechanisms were characterized and analyzed. The results indicate that the initial packing structure before CIP plays an important role in determining the properties of both green compact and Sintered Part after compaction and sintering. Detailed analyses of individual Particles revealed that the Particles with larger deformation tend to generate greater stress concentration during CIP and sintering; meanwhile, the stress distribution in different location of each Particle also demonstrated that a close relationship exists between the stress concentration/release process of individual Particles and their initial packing structure before CIP.

  • three dimensional mpfem modelling on isostatic pressing and solid phase sintering of tungsten powders
    Powder Technology, 2019
    Co-Authors: Xizhong An, Aibing Yu
    Abstract:

    Abstract Particulate scale three-dimensional CIP and solid phase sintering of tungsten powder in powder metallurgy process was numerically reproduced using MPFEM method. The effects of initial packing structures on the densification behavior of the tungsten powders during CIP and sintering were systematically investigated. Various macroscopic and microscopic properties including relative density, overall/local stress distributions, deformation status, pore filling behavior as well as densification mechanisms were characterized and analyzed. The results indicate that the initial packing structure before CIP plays an important role in determining the properties of both green compact and Sintered Part after compaction and sintering. Detailed analyses of individual Particles revealed that the Particles with larger deformation tend to generate greater stress concentration during CIP and sintering; meanwhile, the stress distribution in different location of each Particle also demonstrated that a close relationship exists between the stress concentration/release process of individual Particles and their initial packing structure before CIP.

Norhamidi Muhamad - One of the best experts on this subject based on the ideXlab platform.

  • effects of binder system and processing parameters on formability of porous ti ha composite through powder injection molding
    Materials & Design, 2015
    Co-Authors: Muhammad Rafi Raza, Javad Rajabi, Majid Niaz Akhtar, Abu Bakar Sulong, Norhamidi Muhamad
    Abstract:

    Abstract Porous titanium-hydroxyapatite (Ti/HA) composite is a developed composite material suitable for bio-medical applications. Powder injection molding (PIM) with space holder method is used to produce porous Ti/HA with mechanical properties, similar to human bone, and pores helps to initiate tissue growth. However, the differences in physical and mechanical properties of these composites are the main challenges during debinding and sintering. Therefore, the main objective is to determine effects of binder systems and processing parameters on formability of Ti/HA composite. In PIM, a binder system is necessary to produce green and ultimately Sintered Part. There are two binder systems and variation of sintering temperature has been used. Results revealed that Polyethylene glycol (PEG)-based binder system is applicable with NaCl space holder and optimum sintering parameters, including temperature, heating rate, and holding time of 1300 °C, 10 °C/min, and 5 h, respectively. The fabricated porous Ti/HA exhibits average porosity, pore size distribution, compressive strength, and roughness values of 55%, 60 μm to 170 μm, 370 MPa, and 0.323 μm, respectively. FESEM results showed that the pores are interconnected. It may be an appropriate material for future bio-medical applications.

  • yttria stabilized zirconia formed by micro ceramic injection molding rheological properties and debinding effects on the Sintered Part
    Ceramics International, 2013
    Co-Authors: Farhana Mohd Foudzi, Abu Bakar Sulong, Norhamidi Muhamad, Hafizawati Zakaria
    Abstract:

    Abstract Micro Ceramic Injection Molding (μCIM) is a near net-shape process to produce smaller and intricate Parts at a competitive cost. The application of nano-sized ceramic powder in μCIM has the advantages of fine grain size growth and good surface finish. However, the nano size effect causes agglomeration and low powder loadings, which result in defects during the μCIM process and in the Sintered components. This study extensively investigated the debinding and sintering of yttria-stabilized zirconia (YSZ), as well as its rheological properties, using polypropylene (PP) as the primary binder and palm stearin as the secondary binder. 50 nm Yttria stabilized zirconia (YSZ) powders were mixed with palm stearin and PP at a powder loading of 37–43 vol%. The results of rheological studies showed that the feedstock had a dilatant flow characteristic and a viscosity of around 10–40 Pa s. Feedstock with 38 vol% powder loading had the lowest activation energy of 9.48 kJ/mol. The green Part of the injected feedstock had flexural strength ranging from 13 to16 MPa, within which the feedstock with 43 vol% powder loading had the highest green density. Solvent debinding was carried out at three temperatures (50, 60, and 70 °C) using heptane. A large porous region was clearly identified at 70 °C compared with 50 °C. A debinding split furnace with argon gas was used to remove PP at 450 °C for 4 h. The debound samples did not shrink when 94%–98% of the binder system was removed. All debound samples Sintered at 1350 °C and 41 vol% had the highest mechanical properties with hardness of 900 HV and a flexural strength of 400 MPa.

  • sintering parameter optimization of ti 6al 4v metal injection molding for highest strength using palm stearin binder
    Procedia Engineering, 2013
    Co-Authors: N Mohamad H Nor, Norhamidi Muhamad, A Mohd K A Ihsan, Khairur Rijal Jamaludin
    Abstract:

    Abstract This paper presents an optimization of sintering parameters for the best Sintered strength of Ti-6Al-4 V powder mixed with 60wt% of palm stearin binder and 40wt% of polyethylene by metal injection moulding (MIM) technique. The mechanical properties of the Sintered Part are resulted from tremendous densification of the sample. Sintering parameters have been optimized using Taguchi method of L 9 (3 4 ) orthogonal array. The analysis of variance (ANOVA) was employed to determine the significant levels (α) and its contribution to the variables of the final strength. The study demonstrated that sintering temperature was the most influential variable contributes to the best final strength, followed by heating rate, dwelling time and cooling temperature. Based on these results, samples displayed yield strength of 934.3 MPa, and a plastic elongation of more than 10% were produced. These values meet the requirements of the ASTM B348-02 for titanium alloy medical grade.