热化学反应法制备Al_2O_3-13%TiO_2陶瓷涂层及其性能研究

Preparation of Al_2O_3-13%TiO_2 Ceramic Coating in the Method of Thermo-chemical Reaction and Its Properties

目的研究Al_2O_3-13%TiO_2陶瓷涂层对金属基体的热防护性能。方法以钠、钾混合硅酸盐溶液为粘结剂,添加Al_2O_3、TiO_2、MgO、SiO_2等陶瓷骨料,采用热化学反应法在304不锈钢基体表面制备了Al_2O_3-13%TiO_2陶瓷涂层(记为AT13)。使用扫描电子显微镜(SEM)、X射线衍射仪(XRD)对涂层的微观形貌、物相变化进行表征。在AT13涂层的基础上,预先喷涂金属Ni/Al过渡层,制备了AT13梯度涂层(记为AT13grade),综合比较分析了两种涂层在不同温度下固化后的结合强度,描述了涂层的高温氧化动力学曲线,对涂层的热震性能及失效机理进行了分析。结果涂层在800℃烧结固化后,致密性较好,涂层与金属基体之间呈现冶金结合,TiO_2发生了从锐钛相到金红石相的转变,α-Al_2O_3和金红石型TiO_2是陶瓷涂层耐高温的主体晶相结构。经1200℃高温氧化后,梯度涂层和非梯度涂层的增重与空白试样相比分别减少了0.223 mg/cm2和0.155 mg/cm2。800℃热震试验时,梯度涂层和非梯度涂层的热震循环次数分别为17次和6次。结论在涂层与基体之间制备金属Ni/Al过渡层能增强涂层的结合强度,提高其抗氧化性能,缓解陶瓷材料与金属基体之间的热膨胀系数差异,提高涂层的抗热震性能。梯度结构的陶瓷涂层具有更好的热防护性能。

The work aims to study thermal protective properties of A1203-13%TiO2 ceramic coating to metal substrate. The A1203-13%TiO2 coating （denoted as AT13） was fabricated on 304 stainless steel substrate in the method of thermo-chemical reaction by adding such ceramic aggregates including A1203, Ti02, MgO and SiO2 to Na and K mixed silicate solution as silicate binder. Morphology and phase transformation of the coating were characterized with scanning electron microscopy （SEM） and X-ray diffractometer （XRD）. Based on the AT13 coating, AT13 gradient coating （denoted as AT13grade） was fabricated by pre-spraying metallic Ni/A1 transition layer. Bonding strength of two kinds of coating curing at different temperature were over- ally compared and analyzed, high temperature oxidation kinetics curves were described, thermo-shock resistance and failure mechanism of coating were analyzed. After being sintered and cured at 800 ℃, the coating exhibited perfect compactness, it demonstrated metallurgical bonding with metallic substrate. TiO2 transformed from anatase phase to rutile phase, ct-A1203 and rutile TiO2 were main heat resisting crystal structure of ceramic coating. After being oxidized at 1200 ℃, weight gain per unit area of gradient coating and non-gradient coating decreased by 0.223 mg/cm^2 and 0.155 mg/cm^2, respectively when compared with bare sample, its thermo shock recycle times were 17 and 6 on the test of 800 ℃. Preparing Ni/A1 transition layer between the substrate and coating can enhance bonding strength and oxidation resistance of the coating, improve thermo shock resistant property of coating by mitigating the difference in thermal expansion coefficient difference between ceramic material and metal- lic substrate. Coating with gradient structure exhibits better thermal-protective performance.