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The scope of this work is to synthetize and characterize a WCCoCr/NiCr nanocomposite evaluating its application as protective coating against erosive wear when applied by High Velocity Oxygen Fuel (HVOF). The composite was formed by carbide of tungsten-cobalt-chrome (WCCoCr) processed by high energy milling and a metallic matrix of nickelchrome (NiCr). The milled material was added to the NiCr in the fraction of 5%wt. The powders were investigated by X-ray diffraction and and scanning electron microscopy, analysing particle size distribution and surface area. The protective layers were deposited by HVOF and evaluated for their microhardness, microstructure, porosity, and erosive wear. Their microstructure showed lamellar character, with a low level of oxides and porosity between 0.5 % and 1 %. The coating formed by NiCr and WCCoCr milled for 3 hours presented microhardness of 635 HV and erosion rates 50 % smaller than the commercial coating.

With depleting reserves of high-grade iron ores in South Africa, the local minerals processing industry is increasingly paying attention to fine tailings material as a potential resource for the future. A significant proportion of these tailings consists of slimes, i.e. material finer than 38 μm. Upgrading of slimes by physical separation techniques is usually constrained by low efficiency at such fine sizes. Selective flocculation has the potential of overcoming these constraints to a degree. This paper reports on a study that investigated that potential by coupling selective flocculation with magnetic separation to improve separation efficiencies. The coupled process achieved an improvement in the grade of the magnetic concentrate from 52.3% to 59.2% Fe at much the same Fe recovery. This constitutes an improvement in separation efficiency from about 40% to 57%. These results were achieved under laboratory conditions, confirming the positive indications found in the literature, and give an indication that similar results may be possible at an industrial scale.

Due to their enhanced tribological properties that contribute to an increased useful life of components, martensitic stainless steels are an excellent option for industrial applications such as hydroelectric, petrochemical, civil construction and mineral processing plants. In the present investigation, the erosive wear of AISI 410 martensitic stainless steel is evaluated after thermal treatment by quenching and tempering by mass loss, under erosive attack at 30° and 90° incidence angles, using a self-made jet slurry erosion equipment controlling parameters such as speed, volume of fluid, temperature and concentration of erosive particles of erodent. The characterization of the eroded samples was carried out in terms of the microstructure (SEM) and microhardness as well as the particle size distribution (LG) and morphology of the erodent. It was possible to establish the relationship between the slurry erosive wear and the physical properties inherent of stainless steel for this particular experimental configuration, concluding that the steel presents better resistance to jet slurry erosion wear when compared to austenitic steel commonly used in the industry.