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Arbi Dimyati
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Transmission Electron Microscopy Characterization of High-Temperatur Oxidation of Fe-20Cr-5Al Alloy Prepared by Focused Ion Beam Technique Dani, Mohammad; Untoro, Pudji; Putra, Teguh Yulius Surya Panca; Parikin, Parikin; Mayer, Joachim; Dimyati, Arbi
Makara Journal of Technology Vol. 19, No. 2
Publisher : UI Scholars Hub

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The Focused Ion Beam (FIB) technique was applied for cross section preparation of the oxidized alloy for Transmission Electron Microscopy (TEM) study. Prior to preparation, the specimens of Fe-20Cr-5Al alloy sheet were oxidized in air at 1200 oC for 2 minutes, 10 minutes, 2 hours, and 100 hours. The microstructure and elemental composition of the samples were characterized using TEM equipped with an Energy Dispersive X-Ray Spectroscopy (EDX). The Electron Energy Loss Spectroscopy (EELS) was used to determine of the light elements. The TEM investigation reveals remarkable microstructure evolution of the specimens during oxidation which generally exhibit a typical multi-layer structure. The TEM images, however, can provide detailed description about the phases occur after oxidation such as the Tungsten (W) and the Gallium (Ga) layers on top of the samples obviously formed during FIB preparation, the formation of Al2O3 and Cr2O3 layer, MgAl2O4 spinel, porosity, Zr/Hf/Mg phases or clusters inside the oxide scale. Hence, the FIB technique has been proven to be reliable preparation technique for microstructural and elemental studies of Fe-20Cr-5Al alloy using TEM.
Residual Stress Measurements on the TIG Weld Joint of 57Fe15Cr25Ni Austenitic Steel for Structural Material Applications by Means X-Ray Diffraction Techniques Parikin, Parikin; Ismoyo, Agus Hadi; Iskandar, Riza; Dimyati, Arbi
Makara Journal of Technology Vol. 21, No. 2
Publisher : UI Scholars Hub

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Measurements of residual stress on the 57Fe25Cr15Ni steel plate with no-filler TIG-welding process were carried out. This work was conducted to determine the nature of weld ability in synthesized steel. The bulks were formed in a dimension of 30x20x7 mm3 to ease data retrieval. Results show that the largest residual stress occurred in the weld metal area, amounting to 82.40 MPa with lattice stretching of 0.18%. Conversely, the values decreased to 65.92 MPa and a stretch of 0.14% in the HAZ area. This residual stress is a tensile stress that can reduce the mechanical strength of the material since it adds to the applied loads. This was confirmed by microstructure observations. The carbon content was very high in the dark lines. Weaken materials usually start from this side and could initiate the intergranular cracks that rapidly migrate among its grain boundaries.
Microstructures and Hardness of TIG Welded Experimental 57Fe15Cr25Ni Steel Parikin, Parikin; Dani, Mohammad; Rivai, Abu Khalid; Ismoyo, Agus Hadi; Iskandar, Riza; Dimyati, Arbi
Makara Journal of Technology Vol. 22, No. 2
Publisher : UI Scholars Hub

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The microstructures and hardness of tungsten inert gas (TIG) welded experimental 57Fe15Cr25Ni steel were investigated through optical–scanning electron microscopy analyses and with a hardness tester, respectively. The welding process restructured the constituent atoms into regular and irregular crystal lattices. Rapid cooling of the weld metal allowed the formation of a dendritic (columnar) structure, with porous grains. By contrast, slow cooling influenced HAZ and led to the formation of grain structures. The crystal lattice became more organized and larger than other zones. Meanwhile, the base metal formed circular nets that covered large area inside thick and thin grain boundaries. The diffraction patterns revealed texturing in the weld metal. The crystallite orientation changed from (111) to (200) and (220) planes. The weld metal profile broadened (amorphous) and had full width at half maximum (fwhm) value larger than those in HAZ and the base metal. The weld metal possessed hardness of 121 HV, which is slightly lower than the hardness of the base metal (130 HV). HAZ exhibited the highest hardness value (152 HV). Hardening was influenced by carbon and outer oxygen migration to the grain boundaries, which formed colonies, i.e., chromium carbide, aluminum carbide, aluminum oxide, silicone oxide, and silicon carbide (precipitation hardening). Welding (heat) may change the microstructure and hardness of HAZ and the weld metal region, which would be brittle and very critical in responding to applied loads.
Effects of Plasma Sintering on the Post TIG Weld Joint of Fe-15Cr-25Ni Austenitic Stainless Steel Parikin, Parikin; Dani, Mohammad; Dimyati, Arbi; Insani, Andon; Deswita, Deswita; Aziz, Ferhat; Mardiyanto, Mardiyanto; Mustofa, Salim; Purwanto, Setyo; Adhika, Damar Rastri; Syahbuddin, Syahbuddin; Huang, Ching An
Makara Journal of Technology Vol. 26, No. 1
Publisher : UI Scholars Hub

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Arc-plasma sintering (APS) for 5 s has been applied to the post tungsten inert gas (TIG) weld joint of Fe–15Cr–25Ni austenitic stainless steel (ASS). The treatment is intended to observe the effect of heat generated by plasma on micro-crystal structures around the fusion zone (FZ), especially internal stress relief in steel after being subjected to welding. The effect of stress relief in weld was measured using the neutron diffraction technique. ASS that is predominantly composed of Fe, Cr, and Ni elements, with contents of 57%, 15%, and 25%wt. respectively, was cut into two parts. Both parts were then welded with TIG without filler with a current and voltage of 60 A and 50 V, respectively. After APS for 5 s, the sample was characterized and analyzed using high-resolution powder neutron diffractometer at a high-temperature laboratory facility. The results show that the tensile residual stress decreased with the APS heat input. The residual stresses significantly decreased from 82.40 MPa to 1.21 MPa in the FZ and continued almost evenly from 65.92 MPa to 1.24 MPa in the heat-affected zone (HAZ). The residual stress is a tensile stress that can reduce the mechanical strength of materials. This condition is also applicable to applied loads. A microstructure gives a confirmation that the C element migrates from the FZ to HAZ. The content was very high in dark traces. The C element reacts to Cr and O to form chromium carbide (Cr23C6) and chromium carbonyl (CrC6O6), respectively. It rapidly migrates among its grain boundaries. It may also weaken materials and probably initiate intergranular cracks.
EFFECT OF SINTERING TEMPERATURE ON TUNGSTEN CARBIDE DENSITIES AND POROSITY Ade, Ade Saputra; Hidayat, Imam; Prijono, Kusdi; Dimyati, Arbi; Salam, Rohmad; Rohmat, Nur; Suhendi, Suhendi
Jurnal Teknik Mesin (Journal Of Mechanical Engineering) Vol 13, No 2 (2024)
Publisher : Universitas Mercu Buana

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22441/jtm.v13i2.23016

Abstract

The manufacture of tungsten carbide begins with mixing WC with Co in the milling process and then the compaction process is carried out using a compacting machine. After that, the sintering process is carried out to increase the strength of the material. From various studies it was found that the sintering temperature had an effect on the density of the tungsten carbide produced. The problem is what is the best sintering temperature for WC (Tungsten carbide). This study was intended to analyze the effect of temperature on the density and porosity of tungsten carbide. The research was carried out with a compaction press load of 20 tons with 4 variations of sintering temperature and heating electric current strength, namely 50A -600°C, 60A -800°C, 70A -1000°C and 80A -1200°C. The results of this study prove that the WC sintering temperature has a significant effect on density and porosity. The highest average density of 9.4763 g/ml was achieved by specimens with a sintering temperature of 1.000°C and a current of 70A. Microstructural observations using SEM-EDX also proved that this specimen had the best density compared to other specimens.
Co-Authors Abu Khalid Rivai Ade, Ade Saputra Agus Hadi Ismoyo Andon Insani Bambang Suharno Damar Rastri Adhika Deswita Deswita Ferhat Aziz Huang, Ching An Joachim Mayer, Joachim Kusdi Prijono Mardiyanto Mardiyanto Marzuki Silalahi Mohammad Dani Nur Rohmat Parikin Parikin Pudji Untoro Putra, Teguh Yulius Surya Panca Riza Iskandar Rohmad Salam, Rohmad RR. Ella Evrita Hestiandari Salim Mustofa Setyo Purwanto Sri Harjanto Suhendi Suhendi Syahbuddin Syahbuddin Teguh Yulius Surya Panca Putra, Teguh Yulius Surya