700MPa级高强钢水蒸气条件下的高温氧化行为

采用高温同步热分析仪(TGA) 对高强钢的高温氧化行为进行了系统研究，分析了不同相对湿度条件下氧化质量变化规律，并采用场发射电子探针(EPMA) 表征氧化铁皮厚度、截面形貌及元素分布，同时采用X射线衍射(XRD) 分析氧化层的物相组成.实验结果表明，在1000℃的不同相对湿度条件下，氧化质量变化曲线由线性规律转变为抛物线规律时，曲线出现明显的拐点，拐点处对应的氧化层质量随相对湿度的升高而增加；潮湿气氛促进氧化铁皮内部产生大量的孔洞和微裂纹等缺陷，这些缺陷成为离子扩散通道从而加快氧化反应；水蒸气能促进Si和Mn元素扩散，导致元素富集层扩大.

High Temperature Oxidation Behavior of 700 MPa Grade High Strength Steel Under Water Vapor Condition

High temperature oxidation behavior of high strength steel was systematically studied by high-temperature thermal gravimetric analyzer(TGA) and the law of oxidation weight gain under different relative humidity conditions was analyzed. Electron probe microanalysis(EPMA) was used to characterize the thickness， cross-sectional morphologies and element distribution of oxide scale and X-ray diffraction(XRD) was used to analyze the phase composition of oxide layer. The experimental results show that the form of weight gain curves transformed from linear law to parabolic law， the curves showed an obvious turning point， and the corresponding mass of oxide scale at the turning point increased with the increasing of relative humidity at 1000℃. Vapor promoted the formation of a large number of defects， such as pores and microcracks inside the oxide scale， which became diffusion channels for the ions， thereby accelerating the oxidation reaction. Moreover， the vapor promoted the diffusion of Si and Mn elements， which can leads to the expansion of the element-rich layer.