| Titanium and titanium alloys have lots of advantages,such as low density,high strength,good biocompatibility,and they have been used in aerospace,automotive,medical and many other fields.But the wear resistance of titanium alloys is poor,which limits its wide application in industry to some extent.Plasma electrolytic oxidation?PEO?technology can grow dense oxide porcelain coatings on the surface of valve metals?aluminum,magnesium,titanium,ziconium?and their alloys to improve the surface state of materials.Although the wear resistance of PEO coating formed by plasma electrolytic oxidation of titanium alloy has been improved to a certain extent,it can sustain a low load.In previous studies,PEO coating of aluminum had excellent wear resistance,under the experimental condition with a load of 100 N,it could sustain 1800 s without wear.In this study,an13?m aluminum layer was first applied on the Ti-6Al-4V alloy by magnetron sputtering technology,then PEO process of the aluminized samples were carried out in 32 g·l-11 NaAlO2 and 16 g·l-1Na2SiO3 electrolytes,the wear resistance of PEO coatings was studied.At the same time,the corrosion resistance of the coatings was measured,and compared with PEO coatings of titanium and titanium alloy.Finally,the photocatalytic property of different PEO coatings prepared by titanium in sodium silicate electrolyte was also studied.The coating formed by magnetron sputtering aluminized Ti-6Al-4V alloy treated in 32 g·l-11 NaAlO2 for 4 min showed excellent wear resistance.In the ball-disk friction experiment,the load and roating speed were 10 N and 500 r/min respectively,a steel ball?62 HRC?was selected as the contact metarial,the coating could sustain 1800 s against the steel ball,and the amount of wear can be ignored.However,under the same friction conditions,the PEO coating prepared in 16 g·l-11 Na2SiO3 electrolyte for15 min was worn out and the wear rate reached 3.9×10-44 mm3/?N·m?.The excellent wear resistance of PEO coating formed in sodium aluminate electrolyte is closely to the high growth rate and compact structure of the coating.But the abrasion resistance of coating prepared in sodium silicate electrolyte is weakened due to a large number of pores on the surface.For PEO cocating formed by magnetron sputtering aluminized Ti-6Al-4V alloy treated in 16 g·l-11 Na2SiO3 electrolyte for 4 min,corrosion resistance was evaluated in3.5%NaCl solution,the corresponding corrosion current density is 2.3×10-88 A·cm-2,improved by an order of magnitude compared with Ti-6Al-4V substrate.Nevertheless,for cocating formed by titanium treated in 16 g·l-11 Na2SiO3 electrolyte for 25 min,thickness and the growth rate of coating has been reached 55.1?m and 2.2?m·min-1.The corrosion current density of this coating and titanium was 8.3×10-88 A·cm-22 and5.6×10-77 A·cm-22 respectively,this indicated that PEO coatings have improved the corrosion resistance of material.For PEO cocating formed by titanium treated in 16 g·l-11 Na2SiO3 electrolyte for25 min,under an ultraviolet xenon lamp,after 10 hours,the 8 mg·l-11 methyl orange solution could be degraded by 41%.But the photocatalytic property of compound coating prepared by dipping 0.1 mol·l-11 CdS and blanching at 500?for 30 min could improve to 69%. |
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