Bulan Abdullah

Mechanical Properties of Aluminium Foam by Conventional Casting Combined with NaCl Space Holder

The purposes of this study were to determine the correlation of the aluminium foams mechanical properties in terms of the effect between its density and porosity as well as between its compressive strength and energy absorption of aluminium foam produced by space holder technique. The space holder used was NaCl particle with three different sizes and conditions. The space holders were completely filled the cavity prior pouring of molten aluminium by CO2 sand casting. Then, the samples underwent machining process to remove surface imperfection after casting, followed by water leaching in ultrasonic cleaner to remove the space holder. The higher the porosity, the lower the compressive strength but then again it acts as good energy absorption. Aluminium foam using NaCl size range of 10-15 mm has the highest energy absorption.

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.

The Effects on Microstructure and Hardness of 0.28% Vanadium and 0.87% Nickel Alloyed Ductile Iron after Boronizing Process

Boronizing/boriding is a thermo mechanical process which produced protective surface layers to enhance the performance of engineering components utilized in mechanical, wear and corrosion. The present study investigate the microstructure and the hardness of boride layers formed on 0.28% Vanadium and 0.87% Nickel alloyed ductile iron after boronizing process. Specimens were boronized at 950° C for 6, 8 and 10 hours holding time before being cooled in the furnace. The microstructure and boride layer formed on the surface of substrates were observed under Olympus BX60 Optical Microscope. Vickers Micro Hardness Tester was also performed to determine the hardness of boride layers. Boride layer was formed by diffusion of the boron into the metal lattice at the surface which composed double phase of FeB and Fe2B with saw-tooth morphology. The results of this study indicated that the thickness of boride layers increased from 109.8μm at 6 hours to 195.4μm at 8 hours holding time before they crack at 10 hours. The hardness of the material surface also increased from 1535 HV to 1623 HV at 6 and 8 hours respectively. In conclusion, the microstructure, borides thickness and hardness of borides layer were depending on boronizing time while temperature kept constant.

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.

The Effect of Surface Treatment on 0.16% Chromium and 1.32% Nickel Alloyed Ductile Iron (Di) through Boronizing Process

This paper aim to investigate the effect on microstructure, hardness and wear (slurry erosion) of alloyed ductile iron (DI) with addition of 0.16% Chromium and 1.32% Nickel before and after boronizing process. The specimens were prepared by melting the Ductile Iron compositions through CO2 sand casting method. Specimens were fully coated with boronizing paste and heated at 850°C and 900°C for 8 hours holding time. Microstructures of the specimens were observed under Olympus BX 41M Optical Microscope. Vickers Micro Hardness Tester was used to determine the hardness of the specimens while Wear Test (Slurry Erosion) to measure the wear volume of each specimen. After boronizing process, the boron element diffused into the specimens which make the surface harden. The thickest boride layer was detected at sample with temperature 900°C. The samples of 900°C give higher hardness than temperature 850°C which is 2909 HV and 1395 HV respectively. Referring to surface roughness test, samples boronized at 900oC had high wear resistance compared to sample boronized at 850oC and as cast. The selection temperature in boronizing treatment can prevent the rate of wear thus can identify the hardness of surface in order to prolong the equipment and application or even structure.

Effect of shot blasting on paste boronizing of 316L stainless steel

This investigation was conducted to study on the effect of shot blasting on the case depth of boride layers produced and microhardness after performing paste boronizing on 316L stainless steel. 250 micron diameter of glass beads had been used in the process of shot blasting with variation in the blasting pressure. Paste boronizing was performed at 850°C with 8 hours of soaking time. The samples involved were tested and analyzed on the microstructure and microhardness. Boride layers of FeB and Fe2B formed due to paste boronizing improve the microhardness of 316L stainless steel and the effect of shot blasting with increasing the blasting pressure increase both of case depth of boride layers and microhardness on the studied metal.