Abstract
In order to enhance wear properties of Al-Zn-Mg-Cu alloy parts, Al2O3-MoO2-SiO2 composite ceramic coatings are formed on Al-Zn-Mg-Cu alloy by the DC micro-arc oxidation (MAO) method in the silicate electrolyte with sodium molybdate. Effects of sodium molybdate concentration on the structure characteristics and wear resistance of the composite ceramic coatings are analyzed by scanning electron microscopy, X-ray diffraction and the wear test, respectively. Analyses indicate that the composite coating consists of different states of Al2O3, MoO2 and mullite phase. With the addition of molybdate in the electrolyte, the morphology and structure are changed. The tribological behavior is greatly affected by the surface characteristics and hardness of the coatings. The composite coatings formed by adding 3 g/L of sodium molybdate electrolyte have the best wear resistance.
Highlights
Al-Zn-Mg-Cu alloys are widely used in marine applications due to their superior performance [1,2,3,4,5]
The micro-arc oxidation (MAO) process can be carried out using direct current (DC), pulsed DC regimes or alternating current (AC) [18,19,20]
To improve the wear properties of the Al-Zn-Mg-Cu alloy, in this study, Al2 O3 -MoO2 SiO2 composite coatings were formed through DC MAO treatment in a silicate electrolyte containing Na2 MoO4
Summary
Al-Zn-Mg-Cu alloys are widely used in marine applications due to their superior performance [1,2,3,4,5]. Proper surface treatments are necessary, such as conversion coating, electroless Ni-P coating, silane coating, micro-arc oxidation (MAO) and so on [10,11,12,13,14,15,16,17] Among these methods, MAO is widely used because of its excellent performance, such as environmentally friendly process, superior corrosion and wear properties, etc. Li et al [26] report that the MAO coating formed in the silicate-based electrolyte containing Na2 MoO4 can enhance the wear properties of the Mg-Li alloy due to the addition of molybdenum oxide, compensating the structural defects of the MAO coating. The present work is an attempt to incorporate molybdate into silicate-based electrolyte to form an Al2 O3 -MoO2 -SiO2 composite ceramic coating on the Al-Zn-Mg-Cu alloy by the DC MAO technique, with interest in the structure characteristics and tribological behavior of the composite ceramic coating with different molybdate contents
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