增材制造Ti6Al4V合金的闪速等离子体电解氧化与在生理介质中的电化学行为

Flash plasma electrolytic oxidation and electrochemical behaviour in physiological media of additive manufacturing Ti6Al4V alloy

研究激光粉末床熔融增材制造(AM)(又称直接金属激光烧结)技术制备的Ti6Al4V合金等离子体电解氧化(PEO)处理及其电化学行为。通过短时间(<120 s)PEO处理(也称闪速PEO),在AM合金和传统合金表面制备了3~10μm厚、含Ca和P的涂层。然后在改良的α-MEM溶液中,通过动电位极化曲线和电化学阻抗谱(EIS)评估了合金的电化学行为。与传统合金相比,AM合金中形成了细小的层片状α显微组织和层间小尺寸的β相颗粒,这促使了火花的产生,从而促进了PEO涂层的生长。闪速PEO涂层提高了传统合金和AM合金的耐腐蚀性,最薄的涂层(<3μm)提供了高达3倍的保护。AM Ti6Al4V由于其高的晶界密度,易受局部缝隙腐蚀的影响。而即使短至35 s的闪速PEO处理也足以成功避免这种情况。

The objective of this work is to understand the plasma electrolytic oxidation(PEO)treatment and electrochemical behaviour of a Ti6Al4V alloy manufactured by a laser powder bed fusion additive manufacturing(AM)technique known as direct metal laser sintering(DMLS).Ca and P-containing coatings were produced with short time(<120 s)PEO treatments(also termed as Flash-PEO)obtaining 3-10μm-thick coatings on both the AM alloy and a conventional counterpart.Subsequently,the electrochemical behaviour of the bare and treated alloys was assessed in a modified α-MEM solution via potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The fine α-lamellar microstructure of the AM alloy with small β-phase particles at the interlamellar spaces was seen to advance the onset of sparking promoting faster growth of PEO coating in comparison to the conventional alloy.Flash-PEO coatings enhanced the corrosion protection of both conventional and AM alloys,the thinnest(<3mm)coatings providing up to three times greater protection.AM Ti6Al4V was found to be susceptible to localized crevice corrosion which could be assigned to the high grain boundary density.Flash-PEO treatments,even as short as 35 s,were sufficient to successfully prevent it.