摘要
热喷涂技术作为零部件表面强化的重要技术,在提升零部件耐磨、耐腐蚀、耐高温等综合性能,延长零部件的使用寿命等方面发挥着重要作用。但热喷涂成形过程中焰流温度高、能量密度集中易使涂层/基体体系累积大量热量,进而导致涂层出现热裂纹甚至开裂、剥落等现象,降低涂层的服役可靠性和缩短涂层的工作寿命。针对热量累积造成涂层质量下降的问题,目前研究焦点为探究热喷涂成形过程热量累积行为并对涂层/基体体系进行温度场监控,以掌握体系温度场动态变化过程。根据体系热量累积规律,调节喷涂工艺参数并加载冷媒介质来实现涂层成形过程的温度控制是提升涂层成形质量的重要方法,为涂层成形过程创造良好的外界环境,解决涂层/基体热量累积的难题。近年来研究人员综合应用数值模拟与实验测试方法探究热喷涂成形过程中涂层/基体体系热量累积行为,研究其温度演变规律。基于数值模拟高效率、形象直观的特点,研究静态喷枪在不同喷涂距离、不同基体物性参数等条件下基体表面与截面温度场分布。在此基础上,研究动态喷枪不同加热运动轨迹对体系热量累积的影响,以及考虑涂层动态逐层搭接堆垛过程体系的温度变化。本文还归纳了多种测温设备在基体/涂层体系温度测量中的适用性及优缺点。还有学者分析了喷枪移动速度与运动轨迹对体系热量累积的影响,并力图通过控制喷涂工艺使体系温度处于合适范围。在综合对比压缩空气冷却、水冷却与干冰喷射冷却等不同冷媒介质对体系温度控制优缺点的基础上,提出干冰冷却具有洁净与散热的双重作用,可大幅度提升涂层的综合性能。本文归纳了热喷涂成形过程热量累积行为与温度控制的研究现状,其中热量累积行为研究主要通过数值模拟与实验测试进行,而温度控制主要是基于喷涂工艺优化与采用合适的冷媒介质冷却展开,分析了目前理论研究与实验测试中的不足。总体上,数值模拟在预测喷涂成形过程中涂层/基体体系的温度场演变规律,特别是针对喷涂件形状不规则或喷枪运动轨迹复杂的场合具有广阔的应用前景。
T hermal spraying technology is an important technology for surface enhancement of parts, which can be used to improve the comprehensive performance of parts such as wear resistance, corrosion resistance and high temperature resistance, and prolong the service life of parts. However, there exists deficiency including high temperature of flame and concentrated energy density during the forming process of thermal spraying, which makes the coating/substrate system accumulate a lot of heat. It leads to thermal cracks, even cracks, stripping and other phenomena of the coating. Thus the service reliability and working life of the coating were reduced. It is needed to solve the problem of coating quality degradation due to heat accumulation. The recent research focus is to study the heat accumulation behavior during the forming process of thermal spraying and monitor the temperature field of the coating/substrate system. According to the heat accumulation law of the system, the temperature control of coating forming process can be realized by adjusting the spraying process parameters and implementing the cold medium, which is an important method to improve the quality of coating forming, create a good external environment for coating forming process, and solve the problem of coating/substrate heat accumulation. In recent years, researchers have explored the heat accumulation behavior of coating/substrate system and studied the regularities of temperature evolution in the forming process of thermal spraying by applying numerical simulation and experimental testing methods comprehensively. Based on the characteristics of high efficiency and direct visualization in numerical simulation, the temperature distribution of the substrate surface and section was studied when the static spray gun sprayed at different distances and different substrate physical parameters. On this basis, the influence of dynamic spray gun on the heat accumulation of the system was studied in different heating trajectories, and the temperature change of the system was considered in the layer by layer stacking process of coating. This paper also summarizes the applicability, advantages and disadvantages of various instruments in measuring the temperature of substrate/coating system. Some scholars have analyzed the influence of the moving speed and trajectory of the spray gun on the heat accumulation of the system and tried to control the system temperature in an appropriate range through the spray process. Based on a comprehensive comparison of the advantages and disadvantages of different cooling media such as compressed air cooling, water cooling and dry ice jet cooling on the temperature control of the system, it is proposed that dry ice cooling has the dual functions of cleaning and cooling, which can greatly improve the overall performance of the coating. This paper summarizes the research status of heat accumulation behavior and temperature control in thermal spraying forming process. The research on heat accumulation behavior is mainly carried out through numerical simulation and experimental testing, while the temperature control is mainly carried out based on the optimization of spraying process and the adoption of appropriate cold media for cooling. The deficiencies in current theoretical research and experimental testing are analyzed. In general, numerical simulation has an important application prospect in predicting the evolution regularity of temperature field of coating/substrate system in spray forming process, especially in the case of irregular shape of spray parts or complex trajectory of spray gun.
作者
丁述宇
马国政
陈书赢
何鹏飞
王译文
王海斗
徐滨士
DING Shuyu;MA Guozheng;CHEN Shuying;HE Pengfei;WANG Yiwen;WANG Haidou;XU Binshi(National Key Laboratory for Remanufacturing, Army Academy of Armored Forces, Beijing 100072;National Key Laboratory of Human Factors Engineering, China Astronaut Research and Training Center, Beijing 100094)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2019年第21期3644-3653,共10页
Materials Reports
基金
国家自然科学基金(51675531
51535011)
北京市自然科学基金(3172038)~~
关键词
热喷涂
热量累积
温度控制
数值模拟
冷媒介质
thermal spraying
heat accumulation
temperature control
numerical simulation
cold medium
