Siti Khadijah Alias

The Effect of Carburizing Medium on Carbon Dispersion Layer of ASTM A516 Steel

Carburizing had been a renowned case hardening method for most metal which produced hard casing protecting the surface, resulting in improvement of the mechanical, wear and corrosion behaviour. Carburizing in solid medium offer low cost advantages, thus it is widely implemented. The objective of this study is to compare the carbon thickness layer formed after carburizing process at two different solid medium which is powder and paste form. ASTM A516 Grade 70 mild steel was use as the sample in this study. Carburizing process in both powder and paste medium are conducted at three different temperatures which are 850°C, 900°C and 950°C for 8 hours holding time and cooled in room temperature, for comparison purpose. The thickness layer observation and measurement was carried out using optical microscope and XRD analysis was also conducted to validate the carbon appearances. Rockwell hardness test was also performed before and after carburizing process. The findings from this study indicated that paste carburized samples induced deeper carbon diffusion compared to powder carburized samples. Higher carburizing temperature is also favorable in enhancing the thickness layer in both powder and paste carburized samples. It could be stated that comparable thickness layer could be achieve faster in paste carburized samples, compared to powder carburized samples, which can lead a more cost effective carburizing process.

Tensile strength properties of niobium alloyed austempered ductile iron on different austempering time

This study focused on tensile strength properties inclusive of ultimate tensile strength and elongation values of niobium alloyed ductile iron in as cast and austempered conditions. The tensile specimens were machined according to TS 138 EN 10002-1 standard. Austempering heat treatment was conducted by first undergoing austenitizing process at 900°C before rapidly quenched in salt bath furnace and held at 350°C for 1 hour, 2 hours and 3 hours subsequently. The findings indicated that austempering the samples for 1 hour had resulted in improvement of almost twice of the tensile strength in niobium alloyed ductile iron. Improvement of elongations values were also noted after 1 hour austempering times. Increasing the austempering holding times to 2 hour and 3 hours had resulted in decrement in both tensile strength and elongations values.

Slurry wear test of long kenaf polyester composite (LKPC) and long kenaf polyester with fiberglass composite

This paper presents an experimental study on the influence of fiberglass woven in Long Kenaf Polyester Composite (LKPC). Wear and friction characteristics were examined using sea water and sand as a slurry. Wear test were carried out using Slurry Erosion Test Rig (TR-40). These tests were performed at room temperature with speed of 200 rpm for every 2 km interval. The results from the tests show that mass loss were depends on the matrix composition of the composite. Surface Roughness, Ra, was consistently reduced after each test in all cases.

Storage Modulus Analysis of Kenaf Fibre Reinforced Epoxy Composites

This article presents the storage modulus analysis of kenaf fibre composites that reinforced by two different epoxy matrix systems, named epoxy A and epoxy B. These epoxies are commercially available in Malaysia and been used as a polymer matrix in composite research. Composites were made from hand lay out technique and undergo storage modulus evaluation by using dynamic mechanical analysis (DMA). Fibre content ratios were found to affect the storage capacity in both reinforced epoxy system. However, the addition of 45% kenaf fibre volume ratios reinforced into Epoxy A composites exhibits only week improvement as compared to its rival. The possibility of causes might be attributed to the week interfacial between fibre and matrix.

Synthesis Route towards Fine and Monodisperse Ni Nanoparticles via Hot-Injection Approach

Manipulation of adding sequences have been found to influence the reaction rate, thus made it easier to produced controllable Ni nanoparticles. Hot-injection approach shown capability to significantly reduce the production time of Ni nanoparticles compared to the conventional one-pot synthesis. With minor modification on conventional polyol method, narrow, monodispersed and highly yield spherical nickel (Ni) nanoparticles were successfully produced at synthesis temperature of 60°C. Three mixing methods were investigated to study its efficiency towards producing rapid and narrower size distribution of Ni nanoparticles. Reduction processes were proposed each of the method. As-synthesized Ni nanoparticles were characterized with Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM) and Fourier transform infrared spectroscopy (FTIR) to analyze the size, morphology and interaction of reactants. Fine particles size distribution revealed that when hydrazine was first heated, reaction rate improved tremendously.

Boron Dispersion Layer of Paste Boronized 304 Stainless Steel before and after Shot Blasting Process

Boronizing had been extensively used in enhancing the properties of metallic material such as steel by formation of hard casing on the surface of the substrate. This study highlighted the effect of applying surface deformation process which is shot blasting on the dispersion layer of paste boronized 304 stainless steel. Boronizing treatment was conducted using two different temperatures which are 850°C and 950°C for 6 hour holding time. Shot blasting process was conducted onto the surface of the samples before boronizing process in order to allow deeper boron dispersion layer. Microstructure and boron dispersion layer measurement were then accomplished using optical microscope. XRD analysis was performed to validate the existence of Fe2B phases and Rockwell hardness test was also conducted to obtain the hardness values. The results indicated that combinations of high boronizing temperature and shot blasting process facilitate deeper dispersion layer. Deeper dispersion layer are paramount as it will enhanced the hardness and wear properties.

XRD Evidence for Phase Structures of Niobium Alloyed Austempered Ductile Iron

This paper presents the changes on phase structures of niobium alloyed ductile iron after austempering process which started by austenitizing process at 900°C and held at 350°C for 1 hour, 2 hours and 3 hours in salt bath furnace. The phase structure were observed by light microscope, and then verified through X-Ray diffraction (XRD). The phase structure of as cast niobium alloyed ductile iron mainly consists of graphite nodules embedded in ferrite and pearlite phases with presence of niobium carbide. Austempering process resulted in the structure of graphite nodules embedded in ferrite platelets and bainitic structures. Increasing the austempering holding times had resulted in coarsening of the ferrite platelets structures and transformation from lower bainite to upper bainite structures.

Development of High Strength Ductile Iron with Niobium Addition

The studies emphasis on the development of niobium alloyed ductile iron with higher strength comparing to unalloyed ductile iron. 0.5wt% to 2wt% niobium were added into mixture of ductile iron casting containing pig iron, carburizer and steel scrap, and nodulized through 1.6wt% Fe-Si-Mg addition in CO2 sand casting process. Samples were then machined according to TS EN 10001 standards for tensile test and ASTM E23 for Charpy impact test. In addition, Rockwell hardness test was also performed. Microstructure observations were made after 2% Nital chemical etched and the phase structures were validated through XRD analysis. It was found that addition of niobium in ductile iron provide significant enhancement in mechanical properties when compared to unalloyed ductile iron. Addition of higher amount of niobium had further increased the strength and impact toughness properties. The enhancement of the mechanical properties is expected to further expand the applications of ductile iron.

Investigating the mechanical properties of 0.5% copper and 0.5% Nickel Austempered Ductile Iron with different austempering parameters

The purpose of this research is to investigate the mechanical and corrosion characteristics of Ni-Cu alloyed Austempered Ductile Iron before and after austempering process. Specimens of ductile iron and 0.5% Cu-Ni ductile iron were produced through conventional CO2 sand casting method. The specimens were then austenitized at 9000C before austempered at 3500C at three different holding times which were 1 hour, 2 hours and 3 hours subsequently. The corrosion characteristics of newly developed material were obtained by means of polarization test and the mechanical testing involved tensile test (TS 138 EN1002-1), Rockwell hardness test and Charpy Impact test (ASTM E23). Density test as well as microstructure and SEM observations were also done to ductile iron and Cu-Ni alloyed ductile iron samples. All the testing was done to both as cast and austempered specimens. Addition of copper and Nickel was found to slightly increased the mechanical properties due to solid strengthening effect of Copper and Nickel. The results also indicated that austempering process at 1 hour gives the optimum mechanical properties in term of tensile strength and impact properties compared to other specimens. Increasing the austempering holding times to 2 hours and 3 hours, in contrast had resulted in decrement of the mechanical properties. There are however only slight improvement in hardness properties and no significant effect on density properties of the specimens.

Effect of Pack Boronizing on Microstructure and Microhardness of 304 Stainless Steel

The implementation of boronizing in low alloy steel had been implemented tremendously in past years as this method offers excellent surface protection that led to enhancement of hardness and wear of the material. In conjunction to that, few parameters had been recognized as the factor that promotes boron diffusion into the surface of the material which is the selection of boronizing temperature and time. This study concentrated on the effect of pack boronizing on the boride layer thickness of 304 stainless steel which contained high amount of alloying elements. The microstructural analysis and boron layer thickness was measured and observed using optical microscopy and SEM analyzer. The microhardness of the material was measured using Vickers microhardness tester. The results portrayed that boronizing successfully induced boronizing layer containing FeB and Fe2B phases with thickness of 15μm. This resulted in major improvement of the microhardness values with improvement of 5 times compared to non-boronized samples.