Tribological performance of novel Nickel-based composite coatings with lubricant particles

Abstract The present study is focused on the evaluation of the tribological performance of novel Ni/hBN and Ni/WS2 composite coatings electrodeposited from an additive-free Watts bath with the assistance of ultrasound. Lubricated and non-lubricated scratch tests were performed on both novel composite coatings and on standard Ni deposits used as a benchmark coating to have an initial idea of the effect of the presence of particles within the Ni matrix. Under lubricated conditions, the performance of the Ni/hBN composite coating was very similar to the benchmark Ni coating, whereas the Ni/WS2 behaved quite differently, as the latter did not only show a lower coefficient of friction, but also prevented the occurrence of stick-slip motion that was clearly observed in the other coatings. Under non-lubricated conditions, whereas the tribological performance of the Ni/hBN composite coating was again very similar to that of the benchmark Ni coating, the Ni/WS2 composite coatings again showed a remarkable enhancement, as the incorporation of the WS2 particles into the Ni coating not only resulted in a lower coefficient of friction, but also in the prevention of coating failure

Effect of Thermally-Induced Surface Oxidation on the Mechanical Properties and Corrosion Resistance of Zr60Cu25Al10Fe5 Bulk Metallic Glass

The electrochemical corrosion resistance (in NaCl solution) and mechanical behavior of Zr60Cu25Al10Fe5 metallic glass are modified by the controlled growth of a protective oxide coating, with tunable thickness, during air-annealing treatments in the temperature range 573–673 K. The oxide layer is mainly composed of ZrO2 and Al2O3 and is depleted in Cu and Fe oxides. The glassy structure of the as-cast Zr60Cu25Al10Fe5 alloy is preserved underneath the coating after annealing at 623 K whereas partial crystallization occurs at 673 K. The corrosion current density decreases while the size of the capacitive loop in Nyquist diagrams increases as the oxide layers are made thicker. Nanoindentation experiments reveal an increase of hardness, H, reduced Young's modulus, Er , and H/Er ratio (indicative of wear resistance) after oxidation. Oxidation at 623 K results in an optimum mechanical behavior probably due to the nature of the constituent phases, which can be useful for applications where different parts have to operate in contact