基于质能守恒的等离子喷涂熔滴凝聚结构调控及成形粒子层展性质研究

Plasma spraying is one of the most important technologies for surface strengthening and remanufacturing. In this project, the input and conversion mechanism of ‘matter’ and ‘energy’ during spraying formation will be studied based on the principle of mass and energy conservation. Formation mechanism of the condensed structure of droplets will be revealed by research of the mass transport in spraying jet and crystallizing behavior of droplets with different enthalpy and momentum, and an evaluation method for modality of splat will be proposed. At the same time, the generation mechanism of topological structure and defects will be revealed by thorough study of the correlation and physical-chemical reaction of muckle high activity particles. Based on above-mentioned work, considering the material characteristics, spraying conditions and state parameters of droplets, focusing on control of enthalpy and momentum of droplets, taking theoretical calculation and numerical simulation as methods, an innovational process parameters optimization method marked with ‘calculated firstly and adjusted as needed’ will be put forward to replace the conventional method. This project is expected to deeply reveal the heat and mass transfer behavior and formation mechanism of plasma spraying coatings, and to enhance the coating quality and spraying process substantially. Also, this project could provide some important insights on the improvement of more precisely, greener and smarter plasma spraying technology.

等离子喷涂是零件表面强化和再制造的重要技术之一。本项目基于质能守恒原理研究等离子喷涂成形中“物质”和“能量”的输入输出、转移转化机制，通过研究喷涂射流中的质量传输机制和荷能熔滴在不同热焓、动量条件下的凝固结晶行为揭示熔滴凝聚结构形成机理，并提出熔滴铺展形态评价方法。同时，深入研究大量高活性成形粒子间的交互作用、理化反应和层展性质，揭示涂层拓扑结构演化过程和缺陷生成机理。在前述研究基础上，综合材料特性参数、成形过程参数和熔滴状态参数，以喷涂粒子热焓和动量控制为核心，以理论计算和数值模拟为手段，突破传统的“依赖经验、反复试验”的涂层成形工艺优化方法，构建全新的“先理论计算、后按需调整”的涂层成形工艺快速精确赋予方法。本项目有望深入揭示等离子喷涂成形中的传热、传质行为和涂层构筑机理，大幅提升涂层成形质量和喷涂工艺水平，进而为提升等离子喷涂技术的精准化、绿色化、智能化水平提供科学支持。

等离子喷涂作为一类重要的材料表面强化、改性及损伤修复手段，在新品零件先进制造及再制造修复中具有广阔的应用前景。但传统的等离子喷涂存在涂层质量分散性大和工艺优化严重依赖经验等瓶颈问题，涂层质量和性能难以达到“精准制造”的要求，工艺控制手段也难以适应“智能制造”的发展。本项目从等离子喷涂成形中“粒子飞行”和“撞击铺展”两个基本物理过程入手，研究了等离子喷涂的微观成形过程，提出了涂层质量调控方法。研究内容主要包括：观测了飞行熔滴在气-液-固三相流中的成份转变和物相演变现象；探究了高温、高速、高活性飞行熔滴与射流的交互作用和能量传输行为；阐明了熔滴动量、热焓对其在基体表面撞击、铺展、凝固、结合的影响机理；揭示了涂层孔隙、夹杂、微裂纹、局部脱粘、残余应力等典型缺陷形成机理；创新提出了适应涂层基本构成单元—扁平粒子形态参数定量评估、残余应力状态测试及其与基体附着强度测试的系列方法；初步建立了“工艺参数-飞行状态-凝固形貌-涂层质量”映射关系，形成了喷涂工艺参数快速优化和涂层质量精确调控方法。项目研究成果可为更深入地阐述等离子喷涂成形的微观理化过程，掌握涂层典型缺陷形成机理及其调控方法，提升等离子喷涂的涂层质量和工艺水平提供重要支撑。