低温微粒轰击与热喷涂一体化成形技术及涂层性能强化机理

Considering the requirement of coating preparation technologies with perfect properties in the field of mechanical product remanufacturing, an integrated forming method was put forward in this project, namely a low temperature particle bombarding process was in situ added in the process of thermal spraying. This method is expected to realize the property enhancement of the whole coating. The following issues will be focused in the present study: (1) Integrating the forming equipment of a low temperature particle bombarding and a high velocity combustion gas spraying, and realizing the fine control of the key process parameters. The energy matching rules between the particle bombarding and spraying is aimed to study consequently. (2) Modeling the residual stresses for the low temperature particle bombarding assisted thermal sprayed coating. The effect regularities of the bombarding process on the residual stress distribution and its controlling method is also planned to investigate. (3) Developing the interface cohesive strength analyzing model for the integrated forming coating, and the coating interface cohesive strength and its structure transfer regularities will be experimentally characterized. (4) Investigating the coating general mechanical properties, frictional wear and fatigue properties. The correlations between the coating process, structure and properties will thus be analyzed, and the property enhancement mechanism is planed to be described correspondingly. In this interdisciplinary program, the problems such as mass and heat transfer of the spray jet, structure and properties of the coating interface, energy transfer and mechanical response of the process were included. Through the accomplishment of this project, the above regularities can be disclosed, and a new theory and method which can significantly improve the coating quality, i.e. the low temperature particle bombarding and thermal spraying integration forming can be obtained. Also, this project could provide some important insights on the improvement of the coating preparation technologies.

面向机械产品再制造对高性能涂层制备技术的需求，提出在热喷涂动态成形过程中实时引入低温微粒轰击工艺的一体化成形思路，以实现整个沉积层的性能强化。主要研究：（1）低温微粒轰击与高速燃气喷涂一体化装置的集成及其关键参数的精确控制，进而研究微粒轰击与喷涂的能量匹配规律；（2）建立低温微粒轰击热喷涂层的残余应力模型，研究微粒轰击对涂层残余应力分布的影响规律及其控制方法；（3）建立一体化成形涂层界面结合强度分析模型，研究涂层界面结合强度及组织结构转变规律；（4）研究一体化成形涂层的常规力学性能、摩擦磨损性能和疲劳性能，分析涂层成形工艺、组织及性能三者间的基本映射规律，阐释其性能强化机理。本项目体现了射流传质与传热、材料界面组织与性能、能量传输及力学响应等多学科问题的交叉，有望在揭示上述规律的基础上，形成低温微粒轰击与热喷涂一体化成形理论和方法，使涂层质量有大幅度提升，为开拓涂层制备技术提供科学支持。

项目围绕低温微粒轰击与热喷涂成形一体化成形技术展开了研究，探索了传统喷丸工艺与电弧喷涂交替进行的冷微粒轰击强化涂层、掺混轰击微粒的粉末普通火焰及高速火焰喷涂工艺，最后摸索出轰击微粒/喷涂粉末分离式WPPA-HVOF喷涂工艺，自主开发了相应的WPPA-HVOF喷涂枪及控制系统，实现了喷涂沉积动态过程能量传输的精确控制，研究了涂层残余应力行为以及不同成形工艺对涂层界面结构及强度等性能的影响规律。具体结果简述如下：.（1）率先提出并实验验证了轰击微粒与喷涂粉末分离式送入的WPPA-HVOF喷涂工艺，该工艺极大改善了涂层中的残余应力分布状态，同时也带来孔隙率、显微硬度、内聚结合强度等基本性能的改善，可实现涂层综合性能的提升。.（2）WPPA-HVOF工艺中轰击微粒的加入对喷涂粒子的温度和速度影响不明显，而且轰击微粒不会发生熔化，是在固相弹塑性范围内与已沉积粒子发生高速碰撞，产生的冲击作用不会造成已沉积粒子的非晶相结构发生晶化，微粒轰击后都能可靠的发生回弹而不会掺杂在涂层当中，形成的撞击坑也不会影响后续沉积粒子的结合。.（3）WPPA-HVOF工艺制备的铁基非晶涂层具有较好的显微硬度、抗摩擦磨损和接触疲劳等综合性能，特别是在高载荷的作用下（如20N, 5Hz），强化涂层的磨损体积仅为未轰击处理涂层的1/3，但WPPA-HVOF工艺对涂层产生的强化效果并没有改变涂层的磨损机制，其磨损形式仍然以剥层磨损为主。.（4）利用WPPA-HVOF工艺可实现铁基非晶厚涂层的成形，初步试验证实涂层厚度可达8mm以上，组织结构均匀致密，氧化物和孔隙率含量低，且整体非晶含量高达90%以上，平均硬度可达976HV，该工艺为大块非晶合金的制备提供了先进的技术手段。