Materials Science Forum Vol. 819

Abstract: In this paper, dissimilar joining of 316L stainless steel to low carbon steel was carried out using gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW). Samples were welded using AWS: ER309L welding electrode for GMAW and AWS: ER316L welding electrode for GTAW process. Determination of mechanical properties and material characterization on the welded joints were carried out using the Instron tensile test machine and an optical microscope respectively. The cross section area of the welded joint consists of three main areas namely the base metal (BM), heat affected zone (HAZ), and weld metal (WM). It was found that, the yield and tensile strengths of welded samples using ER316L filler metal were slightly higher than the welded sample using ER309L welding electrode. All welded samples fractured at low carbon steel base metal indicating that the regions of ER316L stainless steel base metal, ER316L filler metal and heat affected zone (HAZ) have a higher strength than low carbon steel base metal. It was also found that ER316L welding electrode was the best filler to be used for welding two dissimilar metals between carbon and stainless steel.

Abstract: The effect of Al and Si addition on IMC formation at the solder and Cu substrate interface was investigated. The compositions of the solder alloy used are Sn-0.3 wt.% Ag-0.5 wt.% Cu (SAC0305), SAC0305-1 wt.% Al (SAC0305-1Al), SAC0305-2 wt.% Al (SAC0305-2Al) and SAC0305-2 wt.% Al-2 wt.% Si (SAC0305-2Al-2Si). Solder alloys were prepared by casting process. Melting temperature of each solder alloys was determined using DSC. Reflow process of the solder alloys were carried out at 260 ^oC on Cu substrate. Morphology of the intermetallic compound (IMC) formed at the solder joint was observed using Fe-SEM equipped with EDX. The addition of Al and Si reduced the thickness of IMC layer formed at the solder joint. The addition of 1.0 wt.% Al formed planar shape of IMC while the addition of 2.0 wt.% Al and 2.0 wt.% Al with 2.0 wt.% Si formed scallop shape of IMC. This is due to Cu-Al IMC and Ag-Al IMC scattered near the interface that act as diffusion barriers to Sn diffusion. This suggests that the addition of right amount of Al and Si could form thinner IMC layer that could lead to increase of reliability of solder interconnect.

Abstract: Zinc and its alloy is non-ferrous metal often used as anodic material for the corrosion control in industries. The aim of this research is to determine the corrosion behavior of Zn alloy with different cooling rate during casting process. The three zinc alloys used were Zn-0.5Al, Zn-0.5Al-0.1Mg and Zn-0.5Al-0.3Mg. The cooling rates were varied by pouring the melt into the ceramic and steel moulds. Thermal analysis test was conducted to indentify phase reaction and quantify the cooling rate data. Material characterization and electrochemical test were performed on the cast samples by using standard equipment. The results show that the Zn-0.5Al-0.3Mg cast with fast cooling rate had the lowest corrosion rate compare to others. This indicates that the magnesium addition can improve the corrosion resistance of Zn-Al alloy.

Abstract: Coating possesses superior wear resistance which makes the material suitable for components subjected to dynamic applications under sever wearing condition and high temperature applications. In this study, TiC coating layer was synthesized by preplacing a 1 mg/mm² of fine size (~40 μm) TiC powder on the surface of AISI 4340 steel. The composite layer was produced by rapidly melting TiC powder together with the substrate steel using tungsten inert gas (TIG) torch welding at a fixed heat input of 1344 J/mm. The wear behaviour of the coated steel was investigated using a universal pin-on-disc tribometer. The microhardness profile of the coating showed increment of the hardness value (almost 5 times higher) than the substrate material. The wear test results showed that the TiC coated steel has lower wear volume loss hence, higher wear resistance compared to the substrate AISI 4340 steel. Incorporation of TiC into the steel surface has improved the wear behaviour of the steel by reduction of plastic deformation and ploughing of the steel surface. The SEM micrograph of the wear worn surface showed mild type of abrasive wear for coated steel whereas, the AISI 4340 steel showed severe type wear with excessive plastic deformation and ploughing.

Abstract: Metals are increasingly used in engineering due to their high specific strength. However, some of pure metals do not posses good corrosion resistance. Therefore carbon nanomaterials (CNMs) has been studied to overwhelm the corrosion existed on the metal’s surface. CNMs are synthesized directly on various metal substrates by Chemical Vapor Deposition (CVD) technique without addition of any external catalyst, in reactor at temperature of 800°C. Argon with a flow rate of 200ml/min was used as a carrier gas and acetone as a carbon source. In this study, two different metals were used as metal substrate: mild steel and stainless steel 316. The morphology, existence of CNTs and elemental analysis of the CNMs on metal substrate are evaluated using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Energy Dispersive X-ray (EDX), respectively. It was proven that the different element composition of metal substrate influenced the size and morphology of CNMs. The most suitable metal to grow CNTs was found to be stainless steel.

Abstract: Metal-ceramic composite or cermet coatings have become popular due to their enhanced wear and corrosion resistance properties. Cermet consists of ceramic particulate embedded in a metallic binder. WC-Co coatings are often used in applications that require wear resistance, but there are many applications in which thermally sprayed coatings have been deposited on components that operate under both abrasive and corrosive condition. Thus, in this study, the corrosion behavior of WC-12wt%Co in different electrolyte has been evaluated. Electrochemical test has been done in three electrolytes namely 0.5 M hydrochloric acid, HCl, 0.5 M sulfuric acid, H₂SO₄ and 0.5 M sodium hydroxide, NaOH. It is found that corrosion potential of this coating in acidic environment is more positive compares to in alkaline environment. Both in acid and alkaline electrolyte, binder dissolution were preferential. It may be concluded that this coating have higher corrosion resistance in alkaline electrolyte than in acid electrolyte.

Abstract: In this study, alumina powder of two particle sizes, 1.0 and 3.0 μm were dispersed into the surface layer of pure commercial aluminum sheets by Friction Stir Processing technique (FSP) to produce a composite surface layer of Al/Al₂O₃. The processing parameters such as traverse speed and applied load were kept constant throughout the whole process at 45 mm/min and 10 kN respectively. Samples were subjected to various numbers of FSP passes from 1 to 3. The effect of tool rotation speed, alumina particle size and the number of the FSP passes on material flow were investigated. Mechanical properties evaluation of the surface layer revealed that hardness and strength are a result of the interactions of FSP passes and tool rotational speed. The increments in hardness of the surface layer showed big variation between samples of small alumina particle size and that of larger alumina particle size. Finer particles gave better hardness and strengthening effect than the coarse particles did. Microstructural observations were carried out using optical and scanning electron microscopy (SEM) on samples’ cross sections perpendicular to the tool traverse direction.

Abstract: Complexing agent in the electroless nickel coating (Ni-P) solution plays an important role to maintain the coating deposition rate during the coating process. This paper studies the effect of two complexing agent; sodium citrate and sodium acetate in Ni-P coating. Ni-P coating was prepared in bath containing: NiSO4·6H2O, NaPO2H2·H2O, C2H5NO2, and Pb (NO3)2. Ni-P coating was coated on polished Cu substrate. Morphology, thickness and surface roughness of Ni-P coating were characterized using scanning electron microscope (SEM)/electron dispersive x-ray (EDX), optical microscope (OM), and atomic force microscopy (AFM). The result showed that sodium acetate have higher deposition rate up to 12 μm/h, whereas sodium citrate provided better surface morphology with lower surface roughness.

Abstract: The use of anodized aluminum oxide (AAO) is vastly being explored in recent years. The application includes molecular separation, sensing, energy storage and template synthesis for various nanostructures. The reason AAO is preferred was because of the ability to control the nanopore structure by manipulating some factors during the anodisation process. This study will investigate the exploitation of voltage and anodisation time during the anodisation process and the effect it has on the nanopore structure of the AAO by examining the structure under Field Emission Scanning Electron Microscope (FE-SEM). The experiment was carried out by anodizing aluminum foil in 0.3 M oxalic acid as electrolyte under the constant temperature of 5 °C. The applied voltage was varied from 40, 60 and 100 V with different anodisation time. The outcome of this study demonstrates that applied voltage has a proportional relationship with the developed pore size. Increasing the applied voltage from 40 to 100 V had increased the pore size of the AAO from 38 nm to 186 nm, respectively. Aluminium oxide anodized at 60 V demonstrates pore size in the range of 76 nm. Prolong anodisation time had improved the pore morphology of anodized aluminium oxide in the case of 40 V, however, the pore wall starts to collapse when anodisation time is more than 4 minutes at 100 V.

Abstract: Magnesium alloys create increasing interest in structural application where weight reduction is vast concern. However, one of magnesium drawback in various applications is low corrosion resistance. In general, a hard coating can be applied on metal to combat such a problem. AlN and TiN coatings are most widely utilized in manufacturing area i.e for structural application due to its high hardness, high chemical stability, and excellent adhesion to substrates. Most recent, TiAlBN coating catch many attentions due to its superior properties than other most studied hard coating. The incorporation of aluminium in the cubic face centered TiN structure on Ti sites leads to deformation and strengthening of the crystal structure of the coating together. Moreover, incorporation of BN in this coating should improve and enhanced the corrosion resistance of Mg alloy. Therefore, in this study, TiAlBN coating have been chosen to be deposited on Mg alloy using reactive magnetron sputtering together with AlN and TiN coatings for comparison study. During depositions, target power, working pressure and bias voltage are optimized for each coating. Analysis on the effect of AlN, TiN and TiAlBN coatings on Mg alloy substrate include thickness measurement and microstructure by scanning electron microscope (SEM). Coatings phase were analysed using glancing angle X-ray diffraction analysis (GAXRD) and corrosion properties were evaluated using potentiodynamic polarization in NaCl solution. TiAlBN shows better performance of corrosion protection with the least corrosion rate (penetration rate = 0.20 mm/yr; mass loss rate=0.97g/m²d) in sodium chloride (NaCl) solution although having the lowest coating thickness (412 nm).