Towards a Complete Model of DC Plasma Spray Coating Process

建立直流等离子喷涂工艺的完整模型

• 批准号: RGPIN-2015-06557
• 负责人: Mostaghimi, Javad
• 金额: $ 3.42万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=614219
• 关键词: Towards; Complete; Model; DC; Plasma

Improving the performance of industrial systems depends on the ability of its components to withstand demanding process conditions. For example, to improve the efficiency of a gas turbine, higher engine temperature is required. The maximum operating engine temperature is currently limited by the material properties and not by the combustion process. To enhance the performance of some engine components they are coated with a layer of high melting point, insulating materials that protects them from higher engine temperature. One of the most commonly used techniques to deposit protective coatings is thermal spray coating. This is an enabling technology and its applications are wide ranging and include aerospace, automotive, chemical processing, medical implants, power generation, pulp and paper, etc. One of the most versatile thermal spray techniques is the dc (direct current) plasma spray. The technology is widely used for the deposition of thermal barrier coatings, as well as corrosion and wear resistant coatings. In this process, powder materials are injected into a high temperature plasma jet issued from a plasma torch. The powders are then accelerated, heated and melted before deposited on a component. The quality of the coatings depends on the state of the impacting particles which is a function of the thermal history and trajectory of the powders within the plasma jet. Importantly, the state of the plasma jet is determined by the dynamics of arc fluctuations inside the torch. Thus, the process which leads to the deposition of the coatings has three complementary regions: • Region 1: Plasma torch where gases are heated to high temperatures by a fluctuating arc struck between a cathode and an anode. The amplitude of these fluctuations depends on the type of plasma gases as well as power supply design. • Region 2: Plasma jet region where powders are injected and are heated, melted and accelerated towards the substrate. • Region 3: Substrate region where powders are deposited. The state of the impacting particles is most crucial in determining the microstructure of the deposit. Based on our earlier modeling work, a 3-dimensional, time-dependent integrated model of plasma spray process which includes all three regions of this process will be developed. The model will be able to predict the microstructure of the coating as a function of plasma torch operating conditions. These include the type of plasma gases, flow rate, arc current, powder material and feed rate, powder size distribution, carrier gas flow rate and substrate conditions, e.g., roughness, material, and temperature. The model will try to answer some important questions such as: a) What is the effect of arc fluctuations on the state of impacting particles? b) What is the effect of plasma gas on the amplitude of arc fluctuations and how does it affect particle heating? c) How does porosity forms and what is the size distribution of these pores?

提高工业系统的性能取决于其组件承受苛刻工艺条件的能力。例如，为了提高燃气涡轮机的效率，需要更高的发动机温度。发动机的最高工作温度目前受到材料特性的限制，而不是燃烧过程的限制。为了提高一些发动机部件的性能，它们被涂上一层高熔点的绝缘材料，以保护它们免受更高的发动机温度的影响。最常用的存款保护涂层的技术之一是热喷涂。这是一项使能技术，其应用范围广泛，包括航空航天、汽车、化学加工、医疗植入物、发电、纸浆和造纸等。 最通用的热喷涂技术之一是直流等离子喷涂。该技术广泛用于热障涂层以及耐腐蚀和耐磨涂层的沉积。在该过程中，粉末材料被注入从等离子体炬发出的高温等离子体射流中。然后，粉末在沉积在部件上之前被加速、加热和熔化。涂层的质量取决于撞击颗粒的状态，该状态是等离子体射流内粉末的热历史和轨迹的函数。重要的是，等离子体射流的状态由焊炬内的电弧波动的动力学确定。因此，导致涂层沉积的过程具有三个互补区域： ·区域1：等离子体炬，其中气体通过在阴极和阳极之间撞击的波动电弧加热到高温。这些波动的幅度取决于等离子体气体的类型以及电源设计。 ·区域2：等离子体射流区域，其中粉末被注入并被加热、熔化并朝向基底加速。 ·区域3：沉积粉末的基底区域。撞击颗粒的状态对决定存款的微观结构至关重要。 基于我们早期的建模工作，一个三维的，时间依赖的等离子喷涂过程的集成模型，其中包括所有的三个区域，这一过程将被开发。该模型将能够预测作为等离子体炬操作条件的函数的涂层的微观结构。这些因素包括等离子体气体的类型、流速、电弧电流、粉末材料和进料速率、粉末尺寸分布、载气流速和基底条件，例如，粗糙度、材料和温度。 该模型将尝试回答一些重要的问题，例如： a）电弧波动对碰撞粒子状态的影响是什么？ B）等离子气体对电弧波动幅度的影响是什么，它如何影响粒子加热？ c）孔隙是如何形成的，这些孔隙的尺寸分布是什么？