Abstract:
Wear is a huge problem in the mining industry as it depreciates the assets invested. The industry is looking at efficient refurbishment technologies to repair its equipment so as to enhance its service life. This thesis focuses on the development of wear resistant clads via laser cladding (LC) process to mitigate the problem of degradations in slurry tailings’ pump impeller made of 304L stainless steel. A critical literature review indicates that Tribaloy T-800 and Stellite 6 powders are candidate materials for modifying 304L stainless steel on account of compatibility in the thermo-physical properties of the clads and the substrate. Hence, consolidation behaviour of fiberlaser deposited Tribaloy T-800 and Stellite 6 clads was analysed for chemical homogeneity, microstructural evolution in addition to geometrical characteristics via process maps. Characterisation techniques such as optical microscopy (OM), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) were employed in the analysis of the regions on the process maps with a view to determining the more suitable material in modifying 304L stainless steel substrate. Five regions of consolidation were identified for each coating with varying parameters for different process regions for each coating accounted for by variation in chemical composition. Tribaloy T-800 clads were taken further for quality optimisation of its wear resistance and microhardness on the premise of their superior consolidation behaviour and mechanical properties relative to that of Stellite 6 clads. Taguchi design of experiments (DoE) was implemented for predicting the coefficient of friction (COF), wear resistance and microhardness of laser cladded Tribaloy T-800 clads as feed rate, scan speed and spot diameter were varied. The outcome of this study reveals an optimal combination of parameters for improving the wear resistance of the clads and a good agreement between the predicted and experimental values within acceptable level of significance.
