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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=689604
• 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，为了提高燃气轮机的效率，需要更高的发动机温度。目前，发动机的最高工作温度受材料性能的限制，而不受燃烧过程的限制。为了提高一些发动机部件的性能，它们被涂上一层高熔点绝缘材料，以保护它们免受发动机高温的影响。热喷涂是沉积保护涂层最常用的技术之一。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（直流）等离子喷涂。该技术被广泛应用于热障涂层的沉积，以及耐腐蚀和耐磨涂层。在这个过程中，粉末材料被注入到等离子炬发出的高温等离子射流中。然后将粉末加速，加热和熔化，然后沉积在组件上。涂层的质量取决于冲击粒子的状态，而冲击粒子的状态是等离子体射流中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是由火炬内部电弧波动的动力学决定的。因此，导致涂层沉积的过程有三个互补区域：***区域1：等离子炬，在阴极和阳极之间通过波动电弧将气体加热到高温。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：等离子体喷射区域，粉末被注入并被加热、熔化并加速到基材。***区域3：粉末沉积的基底区域。冲击颗粒的状态是决定镀层微观结构的最关键因素。***在我们前期建模工作的基础上，我们将建立一个三维的、随时间变化的等离子体喷射过程集成模型，该模型包含了该过程的所有三个区域。该模型将能够预测涂层的微观结构作为等离子炬操作条件的函数。这些包括等离子体气体的类型、流速、电弧电流、粉末材料和进料速度、粉末尺寸分布、载气流速和基材条件，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，如：***a)电弧波动对撞击粒子状态的影响是什么？***b)等离子体气体对电弧波动幅度的影响是什么，它是如何影响粒子加热的？***c)孔隙是如何形成的，这些孔隙的大小分布是什么？**