HVAF制备铝基非晶合金涂层及其腐蚀行为研究

Preparation of HVAF prepared Al-based amorphous coating and its corrosion behavior characterization

[目的]为提升2024铝合金表面的耐蚀性能,开展先进涂层制备技术及其腐蚀行为研究。[方法]采用空气超音速火焰喷涂(HVAF)制备铝基非晶合金涂层。通过X射线衍射仪、扫描电子显微镜和透射电子显微镜对非晶涂层及2024铝合金基体的成分、微观结构进行分析。采用电化学工作站监测非晶涂层和铝合金基体在质量分数为3.5%的NaCl溶液中的腐蚀行为,并借助扫描电子显微镜对腐蚀形貌进行观察。[结果]结果表明:HVAF工艺较高的喷涂速度有效降低了涂层的孔隙率(0.35%);同时,较高的喷涂速度使得熔化颗粒的冷却速度高于非晶形成所需的临界冷却速率,极大增加了涂层的非晶含量(高达81.3%)。在质量分数为3.5%的NaCl溶液中,铝基非晶合金涂层的耐蚀性能优于2024铝合金基体,其钝化电流密度为8×10^-6 A/cm^2,点蚀电位约为-0.30 VSCE,低频下的阻抗值约为2024铝合金基体的4倍。铝基非晶合金涂层的腐蚀机制为均匀腐蚀,而2024铝合金基体为点蚀。[结论]HVAF工艺可制备具有高非晶相含量、低孔隙率的铝基非晶合金涂层,能明显改善铝基非晶合金涂层的耐蚀性能。

[Objectives]To improve corrosion resistance of 2024 aluminum alloy,this paper investigates the preparation of an advanced coating and its corrosion behaviors.[Methods]2024 aluminum alloy was coated with an Al-based amorphous alloy coating using high-velocity air fuel spraying(HVAF)technology at high spraying speed.The composition,microstructure and corrosion morphology of the coating and matrix were analyzed using an X-Ray diffractometer,transmission electron microscope and scanning electron microscope,and potentiodynamic polarization plots and EIS curves in 3.5%NaCl solution were measured.[Results]The results indicate that the cooling rate of the melt particles is higher than the critical cooling rate of the amorphous alloy due to the high spraying speed,which greatly increases the amorphous content of the coating.Meanwhile,the high spraying speed effectively reduces the porosity of the coating.The amorphous content of the coating reached 81.3%and the porosity of the coating was low at 0.35%.Moreover,the corrosion resistance of the Al-based amorphous alloy coating was obviously superior to that of the 2024 aluminum alloy with a lower corrosion current density(8×10^-6 A/cm^2)and a higher pitting potential(-0.30 V).The impedance value of the coating was four times that of the 2024 aluminum alloy substrate.The corrosion mechanism of the Al-based amorphous alloy coating was homogeneous corrosion,while that of the 2024 aluminum alloy was pitting.[Conclusions].The high amorphous content and low porosity of the Al-based amorphous alloy coating contribute to its improved corrosion resistance.