Fe-2.2%Si钢在不同气氛下的高温氧化行为

 为了探究硅元素、加热工艺参数(气氛、温度以及时间)对Fe-2.2%Si钢表面氧化铁皮形成过程的复合作用及影响机理,利用热重分析仪(TGA)研究了Fe-2.2%Si钢在600~1 150 ℃干燥空气和水蒸气条件下的高温氧化行为,利用试验得到的氧化增重数据计算出了氧化速率常数和氧化激活能,并建立了氧化动力学模型。此外,还明确了在2种气氛下氧化铁皮的生长机制与结瘤机理。试验结果表明,在2种不同氧化气氛下得到的氧化增重曲线均符合抛物线规律。当氧化气氛中含有水蒸气时,试验钢的氧化速率提高,氧化激活能降低,导致了试验钢的氧化增重增加。在2种氧化气氛下,试验钢的氧化产物均由氧化铁皮和氧化铁皮与基体界面处的富硅层组成,但在水蒸气下得到的试验钢的富硅层疏松多孔,且氧化铁皮中出现大量的孔洞以及裂纹。其氧化机制主要是氧化铁皮生长过程的生长应力以及水蒸气的存在导致生成的H₂向外扩散,造成氧化铁皮出现大量孔洞和裂纹,为氧化介质的扩散提供了通道,有利于气相物质扩散,进而促进了试验钢的氧化行为。此外,由于在氧化铁皮与基体界面形成的富硅层消耗了基体中的硅元素,导致基体表层出现贫硅区,氧化介质可以通过氧化铁皮内部的孔洞和裂纹与基体直接接触,使得该区域基体的氧化速率迅速提高,氧化铁皮厚度迅速增加,从而逐渐形成结瘤形态。

High temperature oxidation behavior of Fe-2.2%Si steel in different atmosphere

In order to explore the compound effect and mechanism of Si elements and heating process parameters(atmosphere,temperature and time) on the formation of oxide scale on the surface of Fe-2.2%Si steel,the high temperature oxidation behavior of Fe-2.2%Si steel under the condition of dry air and water vapor was studied by thermogravimetric analyzer(TGA). The oxidation rate constant and oxidation activation energy were calculated by using the oxidation weight gain data obtained from the experiment. The kinetic model of oxidation was established. In addition,the growth mechanism and nodulation mechanism of oxide scale in two kinds of atmosphere were clarified. The experimental results show that the oxidation weight gain curves obtained under different oxidation atmospheres are in accordance with the parabola law. When there is water vapor in the oxidation atmosphere,the oxidation rate of the experimental steel increases and the oxidation activation energy decreases,which leads to the increase of oxidation weight of the experimental steel. Under two kinds of oxidation atmosphere,the oxide scale of the experimental steel is composed of oxide scale and the Si-rich layer at the interface between the oxide scale and the matrix,but the Si-rich layer of the experimental steel obtained under water vapor is loose and porous,and there are a large number of voids and microcracks in the oxide scale. The oxidation mechanism is mainly due to the growth stress during the growth of oxide scale and the existence of water vapor,which leads to the outward diffusion of H₂,resulting in a large number of holes and cracks in the oxide scale, which provides a channel for the diffusion of oxidation medium and is beneficial to the diffusion of gas phase materials. and then promote the oxidation behavior of the experimental steel. In addition,the Si-rich layer formed at the interface between the oxide scale and the matrix consumes the Si elements in the matrix,resulting in a poor Si zone on the surface of the matrix,and the oxidation medium can contact the matrix directly through the holes and cracks in the oxide scale,so that the oxidation rate of the matrix in this area increases rapidly,the thickness of the oxide scale increases rapidly,and the nodulation shape is gradually formed.