Simulation Supported Process Development for the Deposition of MCrAlY Coatings by Means of the AC-HVAF Process

活化燃烧高速空气燃料（AC-HVAF）工艺是热喷涂工艺的一种变体。颗粒的飞行特性，如颗粒速度和温度，对热喷涂涂层的性能至关重要。AC-HVAF工艺可以缩小高速氧燃料（HVOF）和冷气体喷涂（CGS）工艺在粒子速度和温度方面的差距。它结合了粒子速度和温度，导致沉积涂层的孔隙率和氧化物含量较低，这使得AC-HVAF工艺成为应用高质量MCrAlY涂层的潜在工艺，其中M代表镍、钴或它们的组合。文献中报道的AC-HVAF工艺的高能效，由于沉积速率和沉积效率高，是AC-HVAF工艺的另一个优势。然而，由于缺乏对工艺的理解，该工艺的使用仍然相对有限。颗粒的飞行特性是由燃烧过程和气流决定的。这些过程大多发生在喷枪和喷嘴内部，直接测量是困难的。计算流体动力学模拟是克服这一困难的有效工具。本研究项目的目的是开发合适的交流- hvaf工艺，在CFD（计算流体动力学）模拟的支持下，能够沉积高质量的MCrAlY涂层。CFD模型的建立首先分析了细粒和粗粒CoNiCrAlY原料的喷涂过程。关于捣碎策略和燃烧模型的不同方面将被考虑。将使用颗粒诊断系统测量喷嘴出口后的颗粒速度，以验证所开发的CFD模型。为了验证模型在不同工艺条件下的适用性，将系统地改变工艺参数。该模型将进一步用于开发NiCoCrAlY原料的喷涂工艺，从而进一步验证CFD模型的适用性。因此，如有必要，将进一步发展该模型。本文将研究所选涂层的涂层性能——孔隙率、氧含量和粗糙度及其在等温条件下的行为，以揭示涂层性能与工艺参数或工艺条件之间的关系。这项研究使人们对交流- hvaf过程有了深刻的理解。

The AC-HVAF process (Activated Combustion High Velocity Air Fuel) is one of the process variants of the thermal spraying. The particle in flight characteristics, such as the particle velocity and temperature, are crucial for the properties of thermally sprayed coatings. The AC-HVAF process can close the gap between the High Velocity Oxygen Fuel (HVOF) and Cold Gas Spraying (CGS) process regarding the particle velocity and temperature. It results in a combination of the particle velocity and temperature that leads to a low porosity and oxide content in the deposited coatings, which makes the AC-HVAF process a potential process for applying high-quality MCrAlY coatings, where M stands for nickel, cobalt or their combination. The reported high energy efficiency of the AC-HVAF process in the literature, due to the high deposition rate and deposition efficiency, is a further advantage of the AC-HVAF process. However, the use of the process is still relatively limited due to a lack of process understanding. The particle in-flight characteristics are determined by the combustion process and the gas flow. The majority of these processes takes place inside the spray gun and nozzle, where direct measurement is difficult. Computational fluid dynamic simulation is an efficient tool for overcoming this difficulty. The aim of this research project is the development of suitable AC-HVAF processes, which enable the deposition of high-quality MCrAlY coatings, with the support of CFD (Computational Fluid Dynamics) simulation. The development of the CFD model begins with the analysis of the spraying processes for a fine and a coarse CoNiCrAlY feedstock material. Different aspects regarding the mashing strategy and the combustion model will be considered. The particle velocity after the nozzle exit will be measured using particle diagnostic systems to validate the developed CFD model. The process parameters will be varied systematically in order to verify the applicability of the model under various process conditions. The model will further be used to develop the spraying processes for NiCoCrAlY feedstock materials, which enable the further validation of the applicability of the CFD model. The model will be thereby, if necessary, further developed. The coating properties –porosity, oxygen content, and roughness – of chosen coatings and their behavior under isotherm conditionings will be investigated to reveal the correlation between the coating properties and the process parameters or the process condition. This investigation enables a profound understanding of the AC-HVAF process.