Abstract
Four ceramic coatings are fabricated on 6061 aluminum alloy substrates with a micro-arc oxidation technique in silicate electrolytes with different TiO2 nano-additive concentrations. To explore the cavitation erosion resistance of the micro-arc oxidation (MAO) coating, cavitation tests are performed using a vibratory test rig. After cavitation tests lasting 10 min, the mass losses, surface morphologies, and chemical compositions of the samples after cavitation tests are examined using a digital balance, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), respectively. The results indicate that, in contrast to the aluminum alloy, the MAO coatings, by adjusting TiO2 nano-additive concentration, can decrease the mean depth of erosion rate (MDER) due to the cavitation damage, and lead to an excellent cavitation erosion resistance. The results also show that: In contrast to aluminum alloy, MAO coatings can decrease the MDER due to the cavitation damage in a short period of time by adjusting TiO2 nano-additive concentration. With the increase of TiO2 nano-additive concentration, the compactness and the surface hardness of MAO coatings decrease, which can easily lead to larger erosion pits.
Highlights
Aluminium magnesium alloy, with low density, high strength [1] and a good corrosion resistance [2], receives significant attention in hydraulic machinery, such as ships, pumps and valves
The resulting vapor bubbles or cavities are transported by the flow and subsequently collapse when the pressure recovers to a value above the vapor pressure
If the bubbles collapse adjacent to the solid material surface, it can result in pitting or erosion of the surface and component failure [3,4]
Summary
With low density, high strength [1] and a good corrosion resistance [2], receives significant attention in hydraulic machinery, such as ships, pumps and valves. In these flowing systems, cavitation can occur if the pressure at any location falls below the vapor pressure of the liquid at the operating temperature. With the introduction of hard ceramic coatings by means of micro-arc oxidation, the wear resistance, corrosion resistance, cavitation erosion resistance, and electrical insulation of the metals were increased [9,10,11,12,13]. Nanometer-TiO2 or nanometer-SiO2 as additives were incorporated into coatings or greases, which improved the wear resistance of the protective
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