3Y-TZP/LZAS微晶玻璃功能梯度涂层的微观结构与性能

为了提高钢基体微晶玻璃涂层的韧性, 在Q235钢基体上采用涂搪法制备了钇稳定四方相氧化锆/Li₂O- ZnO-Al₂O₃-SiO₂ (3Y-TZP/LZAS) 微晶玻璃功能梯度涂层。采用XRD、SEM分析了梯度涂层的物相组成和微观结构, 采用压痕法测试并计算了涂层的显微硬度和断裂韧性, 通过粘接-拉伸法测试了涂层的结合强度。结果表明, 3Y-TZP/LZAS微晶玻璃功能梯度涂层各层之间的界面结合紧密; 涂层与钢基体依靠玻璃中的SiO₂与铁的氧化物发生界面反应形成牢固的结合, 反应产物为Fe₂SiO₄和FeSiO₃; 涂层的显微硬度和断裂韧性沿涂层厚度方向逐渐增大, 涂层韧性提高是表面残余压应力增韧、3Y-TZP相变及3Y-TZP的颗粒增韧共同作用的结果; 梯度涂层与Q235的结合强度达16.3 MPa。热震实验表明, 梯度涂层在300℃下经历30余次热循环, 表现出较好的抗热震性能。

Microstructure and Properties of 3Y-TZP/LZAS Glass-ceramic Functionally Gradient Coatings

In order to improve toughness of glass-ceramic coatings, 3mol% yattria-tetragonal zirconia polycrystal/Li₂O-ZnO-Al₂O₃-SiO₂ (3Y-TZP/LZAS) glass-ceramic functionally gradient coatings on Q235 steel substrate were prepared by slurry method. Phase constitution and microstructure of samples were examined by XRD and SEM, respectively. Their micro-hardness and fracture toughness were measured by indentation method. And their bonding strength of the coatings was also investigated by pulling test. Resulting data indicate that the seamless interfaces among toughening coatings, LZAS transition layer and substrate are obtained. SiO₂ in the LZAS glass reacts with iron oxides at interfacial region forming Fe₂SiO₄ and FeSiO₃, which causes tight interface bind between gradient coatings and steel substrate. Micro-hardness and fracture toughness from inner substrate to top surface on the section of the coatings increase gradually. Residual compressive stress toughening, 3Y-TZP particles toughening and 3Y-TZP transformation toughening are the dominant factors for improving fracture toughness of the gradient coatings. Bonding strength of the coatings is up to 16.3 MPa. The gradient coatings withstand more than 30 thermal cycles at 300℃, demonstrating their excellent thermal sock resistance.