Fachhochschule Bielefeld
Composite coatings are widely used in medical, military and commercial application due to their excellent corrosion resistance, mechanical properties, namely, hardness, young’s modulus and their high wear resistance, especially, when introducing nano particles in order to enhance their tribological properties. In the present study, NiB-TiO2 nanocomposite coating has been electrodeposited on tool steel substrate 1.2312 in heat treated condition in order to protect the hammer of barite crushers against wear. TiO2 nanoparticles with an average size of 21 nm were introduced with a concentration of 5 g/l into the bath and dispersed by mechanical stirring. In order to evaluate the tribological performances of the investigated coating, a cyclic impact wear test was conducted under 45° and 90° impact angles for 10 min until 10,000 cycles using an impact-sliding tester. In addition, a tribological wear test has been elaborated using rotating pin-on-disk configuration under a normal load of 10 N with a velocity of 500 rpm for a duration varying between 30 min and 4 hours. The surface morphology, chemical composition and particle distribution throughout the coating were investigated by scanning electron microscopy (SEM). The wear tracks have been analyzed by means of laser scanning microscope (LSM) and SEM with the purpose to determine the damage mechanism. The first SEM results show the successful incorporation of TiO2 nanoparticles in form of agglomerations throughout the coating. The impact sliding results reveal that the wear mechanism depends principally on the impact angle, which will be investigated in detail by means of SEM. Furthermore, the tribological results obtained from the rotative configuration test confirm that the incorporation of the TiO2 nano particles enhances the wear resistance of the coating by increasing the friction coefficient and consequently decreasing the depth of the wear track compared to the pure NiB coating.
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