电解液中Na_2WO_4对Ti_2AlNb微弧氧化膜结构及摩擦磨损性能的影响

选取硅酸盐/磷酸盐体系在Ti_2AlNb表面制备微弧氧化陶瓷膜,利用SEM,XRD,XPS等研究了电解液中Na_2WO_4对氧化膜生长过程、微观结构及成分的影响,同时评价了Ti_2AlNb微弧氧化膜的摩擦磨损行为。结果表明:硅酸盐/磷酸盐电解液中,氧化膜生长速率仅为0.08μm/min,膜层较疏松,表面存在大孔相连的"网状"结构,主要相组成为金红石TiO_2、锐钛矿TiO_2、Al_2O_3及Nb_2O_5。电解液中加入Na_2WO_4,缩短了Ti_2AlNb合金的起弧时间、提高了氧化膜的生长速率、改善了膜层均匀性,同时在膜层中引入了少量WO_3。此外,在Na_2WO_4参与下制备的微弧氧化膜的耐磨性更好。与Si_3N_4对磨时,Ti_2AlNb合金发生严重的磨粒磨损,摩擦因数高达0.5~0.7;含4g/L Na_2WO_4电解液中制备的Ti_2AlNb微弧氧化膜的摩擦因数、比磨损率分别为0.24及6.2×10~(-4) mm~3/(N·m),表面仅出现"鱼鳞状"疲劳磨损特征。

Effect of Na2WO4 in Electrolyte on Microstructure and Tribological Behavior of Micro-arc Oxidation Coatings on Ti2 AlNb Alloy

Micro-arc oxidation (MAO) ceramic coatings were prepared on Ti2 AlNb alloy in silicate/phosphate electrolytes with different concentrations of Na2 WO4 . The influence of Na2 WO4 on the coating growth process ,coating structure and composition was analyzed by SEM ,XRD and XPS .The tribological behavior of MAO coatings was evaluated by the ball-disc wear test .The results show that the growth rate of MAO coating in electrolyte without Na2WO4 is only 0 .08μm/min ,meanwhile ,the coating is loose and rough ,and"networks"connecting with big pores exist on the coating surface .The main phase compositions of this coating are rutile TiO2 ,anatase TiO2 ,Al2O3 ,and Nb2O5 .The addi-tion of Na2 WO4 in the electrolyte shortens the time before sparking of Ti2 AlNb alloy ,increases the grow th rate of the coating ,improves the uniformity of coating and meanwhile ,a small amount of WO3 is introduced in the coating .Besides ,MAO coatings formed in the participation of Na2 WO4 have bet-ter wear resistance .Severe abrasive wear occurs when the test is made on Ti2AlNb alloy with Si3N4 , the friction coefficient reaches 0 .5-0 .7 .Both the friction coefficient and wear rate decrease obviously when Ti2 AlNb is treated by MAO .The friction coefficient and wear rate of MAO coating prepared in the electrolyte with 4g/L Na2 WO4 are 0 .24 and 6 .2 × 10-4 mm3/(N · m ) ,respectively .Only "fish scales" caused by fatigue wear appears on the coating surface.