Masters Degree Dissertations

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Browsing Masters Degree Dissertations by Author "Azizi, Chiriga"

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    An investigation into the causes of premature failure of in-house manufactured high-speed steel tools: a case study of Luwero Industries Limited, Uganda
    (Kyambogo University (Unpublished work), 2024-10) Azizi, Chiriga
    Significant research gaps exist in optimizing High-Speed Steel (HSS) tools, primarily due to a tendency to focus on isolated factors rather than their combined effects, which limits our understanding of machining interactions. Additionally, the lack of empirical validation for theoretical models undermines the reliability of tool performance predictions. Advanced modeling techniques, such as Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD), are often underutilized, and sophisticated microstructural characterization methods, including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), have not been fully leveraged to investigate phase distribution and carbide formation. This study addresses performance discrepancies observed at Luwero Industries Limited (LIL), where in-house HSS tools exhibited significantly lower durability—1,125 rounds per regrind—compared to imported tools, which lasted 4,130 rounds. By examining the combined effects of heat treatment and cutting conditions on tool life—a critical but often overlooked aspect in the existing literature—this research employed advanced characterization techniques, including energy dispersive X-ray (EDX) analysis and two-factor ANOVA with replication, to evaluate carbide formation, morphology, and tool life. The advanced equipment utilized in this study included the Flame Emission Spectrometer (CREATE-9800, 2020), Digital Rockwell Hardness Tester (HRS-150, 2020), metallurgical microscope (OPTIKA B-150, 2020), scanning electron microscope (Carl Zeiss AG, 2022), and Head-turning and Finish-mouth trimming machine (WK-007, 2014). Key findings revealed that imported tools contained higher concentrations of critical alloying elements—particularly carbon, vanadium, and cobalt—resulting in improved hardness and wear resistance. In contrast, in-house tools, while having elevated chromium levels, lacked sufficient carbon, adversely affecting their performance. Heat treatment significantly influenced mechanical properties, achieving a peak hardness of 65.7 HRC at 1300°C; however, increased brittleness at elevated temperatures required careful monitoring. The microstructural analysis underscored the critical role of carbide size and distribution: larger carbides enhanced hardness, while finer carbides contributed to toughness. Effective cooling strategies, especially the use of chilled air, significantly extended tool life compared to dry-cutting methods. Moreover, inconsistent elemental distributions led to premature wear, highlighting the necessity for greater uniformity in manufacturing processes. Overall, this research demonstrates that optimizing elemental composition, heat treatment, and cooling methods can substantially enhance the performance and durability of HSS tools at Luwero Industries Limited. Furthermore, the findings from this research can be applied to similar industries utilizing HSS tools, offering valuable insights for improving production efficiency and reducing reliance on imported tools.