No abstract

The ceramic coatings were prepared by micro-arc oxidation (MAO) on the TiC P /Ti6Al4V composites. The effects of NaOH, C 10 H 12 CaNa 2 N 2 O 8 ·4H 2 O and Na 2 SiO 3 additives in NaAlO 2 and NaH 2 PO 2 solutions on the microstructure, corrosion resistance and wear resistance of the ceramic coatings were investigated, respectively. The results showed that coatings prepared in NaH 2 PO 2 solution were composed of rutile and anatase TiO 2 , while coatings prepared in NaAlO 2 solution consisted of Al 2 TiO 5 , γ-Al 2 O 3 , rutile and anatase TiO 2 . The NaOH addition could increase reaction rate of the micro-arc oxidtion, and the hardness of the MAO coatings could be enhanced by the addition of NaAlO 2 and Na 2 SiO 3 . The thickness of the coatings formed in NaH 2 PO 2 solution is 2-3 times thicker than that of the coating formed in NaAlO 2 solution. The corrosion resistance of the coatings formed both in NaAlO 2 and NaH 2 PO 2 solutions, ranked from additives: Na 2 SiO 3 >C 10 H 12 CaNa 2 N 2 O 8 ·4H 2 O>NaOH. Wear resistance of the coatings formed in the NaAlO 2 solution ranked from the additives: Na 2 SiO 3 >NaOH>C 10 H 12 CaNa 2 N 2 O 8 ·4H 2 O, while the wear resistance formed by NaH 2 PO 2 solution ranked from additives: Na 2 SiO 3 >C 10 H 12 CaNa 2 N 2 O 8 ·4H 2 O>NaOH. After micro-arc oxidation, all of 第 4 期 罗军明, 等: 电解液组分对 TiC P /Ti6Al4V 复合材料微弧氧化膜耐蚀性及耐磨性影响 419 the corrosion resistant and wear resistance of the MAO coatings were higher than those of the untreated TiC P /Ti6Al4Vcomposites. The mciro-arc oxidation coatings formed in NaH 2 PO 2 +Na 2 SiO 3 solution showed the best corrosion resistance (about two orders of magnitude higher than that of the substrate) and better wear resistance.

MgO-ZnO thermal control coatings were prepared on AZ31 magnesium alloy using micro-arc oxidation (MAO) in the electrolyte containing Zn(H 2 PO 4) 2. The influence of current density on the microstructure, composition, adhesive strength, and thermal control performances of MAO coatings were investigated, and the variation of solar absorptance (α s) was examined at different ultraviolet irradiation time. The results show that the MAO coating is composed of MgO, ZnO and a few amorphous phases. With an increase of current density, the number of pores gradually decreases while the roughness increases. As the thickness, adhesion and emittance (ε) firstly increase and then decrease, the changing tendency of α s shows the opposite. When the current density is set at 9 A/dm 2 , the MAO coating exhibits a stronger adhesive strength of 12.6 MPa, a higher ε of 0.872 and a lower α s of 0.363. Moreover, the ultraviolet irradiation test reveals that the α s increases followed by leveling off with increasing irradiation time. This process provides a technical support for fabricating thermal control coating with excellent adhesion, low α s /ε ratio, and good anti-ultraviolet irradiation.