Study On The Friction Performance Of Mao Film On Tc4 Titanium Alloy

In this paper, Adding Na₂WO₄,Na₂MoO₄,NaAlO₂ in Na₂SiO₃-(NaPO₃)₆system respectively,we studied the effects of the solution components on the film ,and the formula of the micro-arc oxidation solution was determined .Under this basis,we studied the effects of pulse parameters(duty cycle,frequency),current densityand oxidation time on the thickness,suface morphology and phase structures of theoxidation films. Besides, the friction behaviour and the effects of micro-arcoxidation film on galvanic corrosion of TC4/metal coupling were examined.The results are as follows: (NaPO₃)₆ played the role of arcing inNa₂SiO₃-(NaPO₃)₆ system . Adding Na₂WO₄ or Na₂MoO₄ could increase thickness offilm. But thickness of film was likely to decrease when the concentrations of Na₂WO₄and Na₂MoO₄ over 2.5g/L and 3g/L respectively.The thickness over 30μm can beobtained when added 1.8 g/L NaAlO₂,but the surface of film was toughirregular .when the sodium aluminate is 1.5 g/L,sodium silicate is 6 g/L,sodiumhexametaphosphate is 5 g/L, we can ensure the thickness of film is over 20μm afteroxidizing for 20min, and the surface of film is uniform and fine.The micro-arc oxidation film that produced in the solution ofNa₂SiO₃-(NaPO₃)₆-NaAlO₂ was mainlycomposed of O,P,Si,Ti,A1;theAl inthe solution was involved in the film-forming ;the phase structures of the film weremalily Al₂TiO₅ and TiO₂(rutile). With the duty cycle increasing,the frequencydecreasing,the current density and oxidation time extending, the thickness of thefilm and the holes of the film added, the micro-pore number decreased and the poresize expanded. The CPS of Al₂TiO₅ enhanced gradually with the increases of dutycycle,the current density and oxidation time.Simultaneously,the proportion ofTiO₂increased. The changing of frequency didn't have siginificant effect on the proportionofAl₂TiO₅/TiO₂.The adhesive wear of the Ti6Al4V alloy is severe, and the COF can achieved0.6. The anti-adhesion effect of the micro-arc oxidation film can decreased the COF in the start stage,the addition of NaAlO₂ can improved the wear resisitance of the film,the COF of coating could be 0.35 when the current density was 6A/dm² and theoxidation time was 30min. When the oxidation time was 10min, the film would betoo thin and not wear-resistant; When the oxidation time was 50min or the currentdensity over 8A/dm², the film would be very rough,and its COF was equivalent tothe COF of TC4.After the coupling of 45 Steel-TC4 ,45 steel were corroded seriously,and thegalvanic corrosion current could reach 13.73μA;There wasn't siginificant sign ofdecay on the surface of 45 steel when it coupled with TC4 that was oxidized,and thegalvanic corrosion current was only1.00μA.After the coupling of duralumin -TC4 ,duralumin were corroded, the galvanic corrosion current was 18.3μA ,and thegalvanic corrosion current declined to 0.95μA when it coupled with TC4 that wasoxidized.Copper could produced passivation when it coupled withTC4, the galvaniccorrosion current was only 0.1μA .When TC4 was oxided, the galvanic corrosioncurrent was close to 0μAwhen it coupled with copper.