Afifah Mohd Ali

Tetragonal and Monoclinic Phase Transformation of ZTA-MgO Ceramic Cutting Tool by Machining Process

The purpose of this study is to investigate the phase transformation route of ZTA-MgO ceramic cutting tool in raw powder form, after sintering process and after machining process. This is to evaluate the effect of phase transformation to the properties of the cutting tool i.e hardness and fracture toughness. Samples of ZTA-MgO ceramic cutting insert were fabricated by wet mixing the materials, and then dried at 100°C before crushed into powder. The powder was pressed into rhombic shape and sintered at 1600°C at 4 hours soaking time to yield dense body. To study the effect of the phase transformation of the fabricated tool, machining was performed on the stainless steel 316L at 2000 rpm cutting speed. XRD analysis were performed on three type of ZTA-MgO samples which were the raw powder, the sintered samples and also the samples after machining process. Results shows that the m-ZrO2 reduced to 0% when sintering process take place and reappear at 12% when the machining process take place proving the occurrence of transformation toughening during the machining process. The consequence of this condition is the hardness of the samples increased by 22% while the fracture toughness decreased by 21.1%.

Effect of Process Parameters on Abrasive Contamination during Water Abrasive Jet Machining of Mild Steel

In the area of grit blasting, it is well known that microscopically small abrasive debris gets trapped on the surface, and due to impact the grits might cause the surface to fracture and a fraction of it to be embedded. The same problem appears in abrasive water jet (AWJ) machining especially in the so-called deformation wear zone or striation zone. The major aim in this study is to investigate the abrasive contamination on mild steel cutting surface. In the present study mild steel was used as the work material, since it is widely used in many industries. In order to analyze the pattern of the contaminations on the cut surface, the selected process parameters were abrasive flow rate, pressure and work feed rate. Abrasive contamination was measured at different depths along the path of the abrasives. The three selected zones for measuring abrasive contamination at different depths were the primary impact zone, the smoother zone and the deformation wear zone. It was found that contamination at the middle zone, i.e., the smoother zone had the least abrasive contamination while the initial impact zone and the deformation wear zone showed high abrasive contamination. It was also found that a higher pressure reduces abrasive contamination while a higher abrasive flow rate and work feed rate increase abrasive contamination.

The Relationship of Cutting Chip Type, Length and Thickness to Wear of Zirconia Toughened Alumina Added with Magnesium Oxide (ZTA-MgO) Cutting Tool

The effect of cutting chips on the performances of ZTA-MgO ceramic cutting tool investigated. nThe aim of this project is to discover the effect of cutting chip type, length and thickness on the wear of the nZTA-MgO cutting tool. CNC turning machining performed by using Rom-Bridgeport CNC turning machine at ncutting speed range from 2250 to 3000 rpm, the feed rate 0.1, 0.3 and 0.5 mm/rev while the depth of cut is nkept constant at 0.2 mm. The flank wear and crater wear were measured accordingly using optical nmicroscope, Matlab programming and SEM. The chip type, length and thickness were classified and nmeasured. The variation of cutting parameters influenced the chip geometry and it relation to tool wear were nanalysed. The chips were collected. The chip type, length and thickness analysed using optical microscope nand SEM. Result shows chip started with tubular and ribbon form of chip. Increment of feed rate, make the nchip break to smaller part. The chip length increase when cutting speed was increased. The chip is 2.49 cm nlength at cutting speed 2250 rpm increased up to 4.61 cm at 3000 rpm. The chip thickness was increased nwith increasing of feed rate where the average thickness is at lowest when the feedrate is at 0.1mm/rev and nhighest at 0.5 mm/rev all cutting speed. The increment of chip length caused the crater wear increased on ncutting tool from 5.66 mm2 at chip length of 2.49 cm and increased to 7.40 mm2 when the length increased to n4.61 cm. The high chip thickness caused higher flank wear on the cutting tool. Based on the analysis, the chip ntype, length and thickness have influence on flank and crater wear of the ZTA-MgO cutting tool which may nlead to failure of the cutting tool.

The Cutting Speed Influences on Tool Wear of ZTA Ceramic Cutting Tools and Surface Roughness of Work Material Stainless Steel 316L during High Speed Machining

The purpose of this research is to find the effects of cutting speed on the performance of the ZTA ceramic cutting tool. Three types of ZTA tools used in this study which are ZTA-MgO(micro), ZTA-MgO(nano) and ZTA-MgO-CeO2. Each of them were fabricated by wet mixing the materials, then dried at 100°C before crushed into powder. The powder was pressed into rhombic shape and sintered at 1600°C at 4 hours soaking time to yield dense body. To study the effect of the cutting speed on fabricated tool, machining was performed on the stainless steel 316L at 1500 to 2000 rpm cutting speed. Surface roughness of workpiece was measured and the tool wears were analysed by using optical microscope and Matlab programming where two types of wear measured i.e. nose wear and crater wear. Result shows that by increasing the cutting speed, the nose wear and crater wear increased due to high abrasion. However, surface roughness decreased due to temperature rise causing easier chip formation leaving a good quality surface although the tool wear is increased.

Role of Ce2Zr3O10 Phase on the Microstructure and Fracture Toughness of ZTA Composites

Despite the impressive development in understanding transformation toughening, tailoring the toughness of zirconia toughened alumina (ZTA) ceramics remained a major challenge. In our research, a simple route based on the powders mixing process of ZTA powders with varying CeO2 additions (0 - 10 wt.%) is developed to investigate this issue. The experimental results clearly reveal that the fracture toughness of ZTA ceramics can be tailored by mixing of ZTA starting powders.