低压冷喷涂铸造缺陷修复涂层性能研究

低压冷喷涂(LPCS)是一种拥有便携式冷喷涂系统的涂层技术。例如DYMET304K系统就应用于这项涂层技术中。通常情况下,压缩空气作为冷喷涂工艺中的运载气体。低压冷喷涂适用于喷涂金属基陶瓷复合粉末,如Cu基、Ni基、Zn基、Al基添加Al2O3粉的复合粉。硬质陶瓷相主要起到清洁喷嘴、增加表面活性和喷丸强化的作用,该方法在尺寸修复领域中具有优势。在这个领域里,修复铸造加工中的缺陷和气孔是一个很热门的应用。例如,Zn基复合材料就适用于防止电化学腐蚀和修复机械损伤造成的尺寸差异。本文对Zn+Al+Al2O3,Zn+Cu+Al2O3和Zn+Ni+Al2O3等复合材料做了实验研究。Zn和Al在腐蚀环境中起到阴极保护的作用,而Cu和Ni也有助于提高材料的机械性能。经过对微观孔蚀电位反应和力学性能(硬度和结合强度)的研究发现,涂层具有相对致密的结构和耐蚀性能。Zn在复合涂层中对其它金属起到阴极保护的作用。此外,在Fe52型铁基材料上的涂层有着足够的力学性能,硬度和结合强度较高。这一类涂层在修复宏观的铸造缺陷上具有很高的潜在应用价值。

Properties of Low-pressure Cold-sprayed Coatings for Repairing of Casting Defects

Low-pressure cold spraying (LPCS) is a coating technique, in which a portable cold spray system, e.g., DYMET 304K system is used to prepare technical coatings. Usually, compressed air is used as the process gas. The LPCS process is an appropriate method for spraying of metallic-ceramic composite powder materials, e.g., Cu, Ni, Zn, Al with additions of Al2O3 particles in the powder blends. The main functions of the hard ceramic particles are cleaning the nozzle, activating the sprayed surface and peening the coating structure. This method has advantages for example in the field of repairing and restoration applications. For that, repairing casting defects and voids is one interesting application of the process. For these purposes, zinc-based composite materials are recommended for restoration and repairing of corrosion and mechanical damages. In this study, Zn+Al+Al2O3, Zn+Cu+Al2O3 and Zn+Ni+Al2O3 composite materials were investigated. Zinc and aluminum give corrosion resistance by cathodic protection whereas copper and nickel will provide also more mechanical resistance. Coating properties, such as microstructures, open-cell potential behavior and mechanical properties (hardness and adhesion strength) were investigated. The coatings have relatively dense coating structures and for corrosion resistance, zinc gives a cathodic protection for other materials in these composite coatings. Furthermore, mechanical properties are sufficient due to the relatively high hardness and adhesion to the Fe52 steel base material. These coatings have high potential in their use as repair materials for macroscopic casting defects.