Development and application of the low critical velocity cold spray process

低压冷喷涂(LPCS)技术已被证明具有就地堆积材料的能力，从几十微米到厘米，改变形成的涂层的成分和特性，并赋予沉积涂层高密度、高导电性和/或耐蚀性。然而，低沉积速率是LPCS工艺尚未解决的主要缺点之一，大大限制了其工业应用。 低沉积速率与颗粒速度有关，这是形成致密涂层所必需的。众所周知，撞击粒子必须超过粒子速度的临界值，即所谓的临界速度，才能在其上沉积，而不是从衬底上反弹。临界速度的大小通常取决于几个因素，包括颗粒和衬底材料的性质、颗粒的温度和大小、颗粒和衬底的表面条件等。特别值得注意的是颗粒表面上存在氧化层和 它的能力会显著影响临界速度。开发一种方法来管理原料粉末材料的临界速度是非常重要的，因为临界速度越低，加速粉末颗粒的沉积速率就越高。该项目提出了通过可控地减小颗粒氧化膜厚度来解决低沉积速率的问题，使用等离子体对原料金属粉末进行预处理。 该项目的总体目标是：(A)开发低临界速度喷涂工艺(LCVS)，使用经过等离子处理的铝和铜基原料粉末组合物，用于Enwin公用事业有限公司，以及(B)将开发的LCVS工艺应用于紧凑的概念验证原型LPCS系统，并提高沉积效率。

The Low Pressure Cold Spray (LPCS) technology has proven its capability of in-situ material build-up from tens of microns to centimeters, varying the composition and characteristics of the formed coatings, and imparting to the deposited coatings such properties as high density, high conductivity and/or corrosion resistance. However, the low deposition rate is one of the main unresolved short comings of the LPCS process, substantially limiting its industrial usage. The low deposition rate is correlated with particle velocity, which is necessary for forming of dense coating. It has been well established that impacting particles must exceed a critical value of particle velocity, called - critical velocity, to deposit on instead of bouncing off the substrate. The magnitude of the critical velocity generally depends on several factors, including particle and substrate material properties, particle temperature and size, particle and substrate surface conditions, etc. Of special interest is the presence of an oxide layer on the particle surface and its ability to considerably affect the critical velocity. Developing a method to manage the critical velocity of the feedstock powder material is very important, because the lower the critical velocity, the higher the deposition rate of the accelerated powder particles. The project offers to resolve the low deposition rate problem by controllably decreasing the particle oxide film thickness, using plasma pre-treatment of feedstock metal powders. The overall objectives of the project are: (a) developing a Low Critical Velocity Spray process (LCVS) by using plasma pre-treated Al and Cu based feedstock powder compositions intended for EnWin Utilities, Ltd., applications and (b) implementing the developed LCVS process into a compact proof of concept prototype LPCS system, with an elevated deposition efficiency.