Cold spray: effect of mixing powders

冷喷涂：混合粉末的效果

• 批准号: RGPIN-2017-05242
• 负责人: yue, stephen
• 金额: $ 3.42万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=711521
• 关键词: Cold; spray; effect; mixing; powders

Cold spray is a seemingly simple method to apply metal coatings to metal, ceramic and polymer surfaces by accelerating metal powders of about 20 to 40 micron particle diameter to supersonic speeds using a carrier gas, usually nitrogen. On impact with the substrate to be coated, the particles severely plastically deform and instantaneously bond to the substrate and each other. The coating of the substrate takes place in air at room temperature. The usual methods to bond powder particles are performed at very high temperatures, between about 80% of the melting point and even upto the melting point, and require very long times, at least a few hours. Clearly the short times and the fact that coatings are done in air are obviously advantageous; room temperature processing means that heat damage is avoided and also means that unlikely materials pairings are possible, such as polymers embedded in a metal matrix. Moreover, very thick 3D coatings can be made, thus elevating the process to one of additive manufacturing. Usually, only one metal powder is sprayed, but this proposal is concerned with what happens when a mixture of powders is cold sprayed. As noted above, interesting composites' can be made by cold spray and part of this work concerns making composites for various applications: metal metal composites for biodegradable stents, metal coatings for lightning strike protection for aircraft structures made of carbon fibre reinforced polymer composites and metal matrix-tungsten carbide composites for wear resistant coatings. The scientific objective, however, is to understand what happens to the cold spray process when mixed powders are sprayed. In this respect we are mainly concerned with the cold sprayability of the mixtures, or how easy it is for these powders to bond onto the substrate to form a thick coating. Cold sprayability is usually judged by the deposition efficiency, i.e. how much of the sprayed powder sticks, and the level of porosity in the coating, the lower the porosity, the better the coating as a general rule. Previous work by our team has shown that the mixing can significantly affect cold sprayability, but in a very unpredictable manner, belying the simplicity of the cold spray concept. This work aims to understand the cold spray mechanisms associated with powder mixing, and use this to develop accurate predictions of cold sprayability. Cold spray is rapidly becoming a key repair' method and, as such, adds to the capacity of technologies for sustainability. As mentioned above, it is one of the additive manufacturing technologies and is therefore of interest to the automotive and aerospace industries. This program is scientifically intriguing and is of great contemporary engineering importance. It represents an excellent training opportunity to generate high quality personnel in the advanced manufacturing sector a vital contributor to the Canadian economy.

冷喷涂是一种看似简单的方法，通过使用载气（通常是氮气）将粒径约 20 至 40 微米的金属粉末加速至超音速，将金属涂层施加到金属、陶瓷和聚合物表面。 在与待涂覆的基材撞击时，颗粒严重塑性变形并立即与基材和彼此粘合。 基材的涂覆在室温下的空气中进行。 粘合粉末颗粒的常用方法是在非常高的温度下进行的，大约在熔点的80%之间，甚至高达熔点，并且需要很长的时间，至少几个小时。 显然，较短的时间以及在空气中完成涂层的事实显然是有利的；室温加工意味着可以避免热损伤，也意味着不可能的材料配对是可能的，例如嵌入金属基体中的聚合物。 此外，还可以制造非常厚的 3D 涂层，从而将该工艺提升为增材制造工艺之一。 通常，只喷涂一种金属粉末，但该提案涉及冷喷涂粉末混合物时会发生什么。 如上所述，有趣的复合材料可以通过冷喷涂来制造，这项工作的一部分涉及制造用于各种应用的复合材料：用于可生物降解支架的金属金属复合材料、用于由碳纤维增强聚合物复合材料制成的飞机结构雷击防护的金属涂层和用于耐磨涂层的金属基体碳化钨复合材料。 然而，科学目标是了解喷涂混合粉末时冷喷涂过程会发生什么。 在这方面，我们主要关注混合物的冷喷涂性，或者这些粉末粘合到基材上形成厚涂层的容易程度。 冷喷涂性能通常通过沉积效率（即喷涂粉末的粘附量）和涂层中的孔隙率水平来判断，一般来说，孔隙率越低，涂层越好。 我们团队之前的工作表明，混合会显着影响冷喷涂性，但影响方式非常不可预测，与冷喷涂概念的简单性背道而驰。 这项工作旨在了解与粉末混合相关的冷喷涂机制，并利用它来准确预测冷喷涂性。 冷喷涂正在迅速成为一种关键的修复方法，因此增强了技术的可持续性能力。 如上所述，它是增材制造技术之一，因此受到汽车和航空航天工业的关注。 该计划在科学上很有趣，并且在当代工程方面具有重要意义。 它为先进制造业培养高素质人才提供了绝佳的培训机会，而先进制造业是加拿大经济的重要贡献者。