Bertero Enrico, Manzano Cristina V, Pellicer Eva, Sort Jordi, Ulfig Robert M, Mischler Stefano, Michler Johann, Philippe Laetitia
Empa - Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures Feuerwerkerstrasse 39 3602 Thun Switzerland
Ecole Polytechnique Fédérale de Lausanne, Tribology and Interfacial Chemistry Group, Materials Institute Station 12 (SCI-STI-SM) 1015 Lausanne Switzerland
RSC Adv. 2019 Aug 16;9(44):25762-25775. doi: 10.1039/c9ra04262h. eCollection 2019 Aug 13.
The electrodeposition of stainless steel-like FeCrNi alloys for miniaturised devices is appealing as it would allow combining excellent material properties ( corrosion resistance, hardness, biocompatibility) at low-cost. However, conventional baths often contain hazardous hexavalent chromium. Cr-based alloys electrodeposited from environmentally friendly trivalent chromium electrolytes are crucial for industrial application for facilitating the transition towards sustainable and ecological production and processing. Nevertheless, this process has not been comprehensively studied or understood in depth: especially the role of organic agents (common additives for improving Cr(iii)-based plating; glycine) in terms of material properties of the electrodeposits. The aim of this work was to investigate the electrodeposition of FeCrNi coatings from a 'green' Cr(iii)-glycine electrolyte. Novel information was attained by analysing films developed under various conditions and characterising them using a combination of advanced techniques. The evolution of microstructure (from amorphous to nanocrystalline) in correlation with film composition ( metals ratio and presence of impurities) and elemental 3D spatial distribution was achieved for coatings produced from different anode materials and thermal post-treatment. The influence of Cr(iii) and glycine in terms of coating atomic contents ( Fe-Cr-Ni-O-C-N-H) was evaluated for films in which both the applied current density and electrolyte composition were varied. These results, together with a thorough analysis on metals speciation/complexation allowed us to propose various Cr(iii)-based electroreduction mechanisms, and to observe, upon annealing, segregation and distribution of impurities, as well as of oxides and metals with respect to microstructure variation, providing an explanation for the amorphisation process.
用于小型化设备的不锈钢类FeCrNi合金的电沉积很有吸引力，因为它能够以低成本兼具优异的材料性能（耐腐蚀性、硬度、生物相容性）。然而，传统镀液通常含有危险的六价铬。从环境友好的三价铬电解质中电沉积的Cr基合金对于工业应用至关重要，有助于向可持续和生态生产及加工过渡。尽管如此，这一过程尚未得到全面深入的研究或理解：特别是有机试剂（用于改善基于Cr(iii)的电镀的常见添加剂；甘氨酸）在电沉积物材料性能方面的作用。这项工作的目的是研究从“绿色”Cr(iii)-甘氨酸电解质中电沉积FeCrNi涂层。通过分析在各种条件下形成的薄膜并结合先进技术对其进行表征，获得了新的信息。对于由不同阳极材料和热后处理制备的涂层，实现了微观结构（从非晶态到纳米晶态）与薄膜成分（金属比例和杂质的存在）以及元素三维空间分布的相关性演变。对于施加电流密度和电解质成分均发生变化的薄膜，评估了Cr(iii)和甘氨酸对涂层原子含量（Fe-Cr-Ni-O-C-N-H）的影响。这些结果，连同对金属形态/络合的深入分析，使我们能够提出各种基于Cr(iii)的电还原机制，并观察到退火后杂质以及氧化物和金属相对于微观结构变化的偏析和分布，为非晶化过程提供了解释。
