激光-感应复合熔覆功能梯度YSZ/MCrAlY热障涂层微结构调控与高温行为的研究

The thermal barrier coatings (TBCs) with high quality are adopted to increase the lifetime of turbines, which has become a problem to be solved urgently in the field of military or civil aircraft. To eliminate the thermal grown oxide (TGO) in the interface of TBCs with a traditional duplex structure, and overcome the common problems such as low efficiency of laser cladding and cracks of cladding layer, the technique of functionally graded YSZ/MCrAlY TBCs produced by laser-induction hybrid cladding has been first put forward by us at home and abroad. Under the condition of cladding efficiency can be increased to 1~5 times higher compared to individual laser cladding, the TBCs prepared by laser-induction hybrid cladding on the different superalloys are systemically investigated. The effects of graded structure, hybrid cladding parameters, composition of MCrAlY, crystalline structure and doped phases on the microstructural growth, evolution and high temperature properties are deeply studied. Moreover, the thermodynamic and kinetic conditions of dual-phase ZrO2/γ-Ni columnar growth are analyzed in detail. The relationship between the interface of electron work function (EWK) and the bonding strengthen are also studied. Theis project is successfully carried out, which can make for furhter understanding a series of scientific problems, suh as the relationship of microstructural control with crystalline orientation and crack susceptibility, and so on. Additionally, this project can also provide the solid theory and practical foundation for establishing the coordinatin mechnism between the microstructural control and high temperature properties, understanding the physical mechanism of functionally graded YSZ/MCrAlY thermal barrier coatings produced by laser-induction hybrid cladding, controlling the quality of TBCs and developing the new coatings.

采用高质量热障涂层提高涡轮机使用寿命，无论在军机或民机上都是亟待解决的关键问题。针对常规双层结构热障涂层热循环时易在界面形成TGO，以及激光熔覆效率低与熔覆层易开裂的难题，本项目在国内外率先提出激光－感应复合熔覆功能梯度YSZ/MCrAlY热障涂层的新方法，在加工效率提高1~5倍的条件下，系统研究不同基材表面热障涂层的制备，深入研究梯度结构、复合熔覆工艺参数、MCrAlY化学成分、YSZ晶体结构与掺杂相对显微组织生长特征、结构演变与高温性能的影响，双相ZrO2/γ-Ni柱状晶生长的热力学与动力学条件，界面功函数与结合强度的关系。本项目的顺利实施，有助于进一步认识微结构调控与晶体取向、生长特征、裂纹敏感性之间的关系等一系列科学问题，为建立微结构与高温性能的协调机制，理解功能梯度YSZ/MCrAlY热障涂层激光－感应复合熔覆的物理机制，控制热障涂层质量及发展新型涂层奠定坚实的理论与实践基础。

采用高质量热障涂层提高涡轮机使用寿命，无论在军机或民机上都是亟待解决的关键问题。针对常规双层结构热障涂层热循环时易在界面形成TGO，以及激光熔覆效率低与熔覆层易开裂的难题，本项目采用在国内外率先提出的激光－感应复合熔覆功能梯度YSZ/MCrAlY热障涂层的新方法，在加工效率提高1~5倍的条件下，系统研究不同基材表面热障涂层的制备，深入研究梯度结构、复合熔覆工艺参数、MCrAlY化学成分、YSZ晶体结构与掺杂相对显微组织生长特征、结构演变与高温性能的影响，双相ZrO2/γ-Ni柱状晶生长的热力学与动力学条件，界面功函数与结合强度的关系。.研究结果表明，当激光－感应复合能量密度E=18.75J/mm2，粉末面密度为ψ＝84.375g/dm2时，在不锈钢与GH4169表面制备了YSZ在MCrAlY层内呈梯度分布的热障涂层，涂层组织致密、与基材呈冶金结合，连续两层间无明显的界面，主要由γ-Ni与t-ZrO2组成。在1050℃热循环氧化过程中，大幅度提高了基材的抗高温氧化性能。建立NiAl的吉布斯自由能关系式：△G = -175700 + 32.2T，Ni3Al的吉布斯自由能关系式：△G = -138100 + 28T。因此，Ni3Al吉布斯自由能始终小于NiAl，所以生成Ni3Al的几率更大。界面功函数与涂层结合强度呈对数线性关系。氧化层主要氧化产物是Cr2O3、Al2O3、NiCr2O4以及少量的Y2O3。在高温热腐蚀（腐蚀介质为Na2SO4）过程中，功能梯度YSZ/MCrAlY热障涂层，发生氧化与热腐蚀，主要发生内硫化腐蚀，生成Cr2O3以及Cr2(SO4)3。.本项目的研究结果，有助于进一步认识微结构调控与高温性能之间的关系等一系列科学问题，为理解功能梯度YSZ/MCrAlY热障涂层激光－感应复合熔覆的物理机制，控制热障涂层质量及发展新型涂层奠定坚实的理论与实践基础。