http://hdl.handle.net/11189/454 2026-09-22T23:31:19Z http://hdl.handle.net/11189/10847 Title: Assessment of the financial feasibility of the rapid sand casting process using the discounted payback period Authors: Msani, Anazo; Nyembwe, Kasongo Didier Abstract: The rapid sand casting of sand moulds has gained significant attention in the foundry industry. However, existing technologies for this process are still quite expensive, and financial assessments are required to justify the adoption of this process in foundries. To that end, a paper was previously published on the financial feasibility of the Voxeljet VX1000 system using the payback period method. This study takes the analysis one step further by considering the time value of money by using a discounted payback period method. The accuracy of the two methods as a means of providing accurate results is compared to guide local foundry men in adopting this process in the local foundry industry. 2024-01-01T00:00:00Z http://hdl.handle.net/11189/10846 Title: Potentiodynamic and electrochemical impedance spectroscopy analysis of hybrid metallic systems in 1 M HCl Authors: Oguntuyi, Samson; Mahlobo, Mandlenkosi G.R.; Akinfolarin, Femi J.; Kibambe, Ngeleshi M.; Nyembwe, Kasongo Didier; Mashinini, Peter M.; Olubambi, Peter Abstract: This study evaluates the corrosion performance of hybrid aluminium components comprising built and substrate regions. The hybrid system, developed via additive and subtractive methods, was divided to separate individual parts for microstructural and electrochemical analysis in 1 M HCl using Open Circuit Potential (OCP), Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP), and Chronoamperometry were used to assess corrosion kinetics, passive film stability, and time-dependent degradation. Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) was used to characterize surface morphology before and after corrosion, identifying phase distribution and localized corrosion. The results pinpoint the electrochemical differences between two hybrid configurations - Sample E (Al 7 built on 6082 substrate) and Sample F (Al 10 built on 6082 substrate), with one typical configuration (Sample E) exhibiting superior corrosion resistance across both its built and substrate regions due to a more stable passive layer and refined microstructure. 2025-01-01T00:00:00Z http://hdl.handle.net/11189/10845 Title: Pitting corrosion study at the built and substrate region of hybrid additive-manufactured Al-Si-Mg alloys Authors: Oguntuyi, Samson; Mahlobo, Mandlenkosi G.R.; Nyembwe, Kasongo Didier; Mashinini, Peter M.; Olubambi, Peter Abstract: Hybrid Additive Manufacturing (HAM) of Al-Si-Mg alloys results in distinct microstructural variations at the built-substrate interface, influencing electrochemical behavior and overall performance. This study investigates the characteristics and corrosion response of as-received built-substrate HAM Al-Si-Mg alloys through microstructural and electrochemical analysis. Thorough microstructural evaluation was carried out using scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), to determine grain morphology and phase distribution in the built and substrate zones. Open circuit potential (OCP), cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) were employed to assess corrosion resistance and pitting susceptibility in natural seawater. The findings provide insights into the role of interfacial microstructure on corrosion susceptibility, contributing to the optimization of HAM-processed Al-Si-Mg alloys for enhanced performance in engineering applications. The outcome revealed that the substrate area showed a refined microstructure with enhanced corrosion resistance in contrast to the built. Also, this study gives a vital understanding of the corrosion behaviour of each region of HAM Al-Si-Mg alloys, which is important for service reliability and structural integrity in aerospace and marine applications. 2025-01-01T00:00:00Z http://hdl.handle.net/11189/10844 Title: Impact of binder jetting process parameters on sand mould friability Authors: Kabasele, Jonathan Kabadjundi; Nyembwe, Kasongo Didier; Mashinini, Madindwa Abstract: The growing application of the binder jetting process for the manufacturing of sand moulds, beyond prototyping, has highlighted the need to understand the effects of process parameters on mould properties. Friability is a crucial foundry property of moulds, related to the resistance of mould erosion during the pouring of liquid metal. In this study, test samples were printed using the Voxeljet VX1000 system and evaluated for friability, with results ranging between 11% and 44%. Artificial Neural Network (ANN) modelling and sensitivity analysis were employed to identify key process parameters affecting friability. AFS (American Foundry Society) grain size emerged as the dominant factor, accounting for 80% of the total impact. Coarser grains significantly improved mould durability by enhancing particle packing and bonding strength. Drop mass (resin concentration) ranked second with a 12% impact, while printhead speed followed closely at 11%. DX (print resolution) exhibited the lowest influence at 6%, indicating that while the distance between drops of binder remains essential for structural integrity, it is not the primary driver of friability. This study is in line with South Africa’s strategy for the implementation of additive manufacturing in the foundry industry. 2025-01-01T00:00:00Z