晶粒尺寸和表面状态对S30432钢蒸汽氧化行为的影响

Effect of Grain Size and Surface State on Steam Oxidation Behaviour of S30432 Steel

利用自制的蒸汽氧化装置对不同晶粒度和表面状态的S30432钢管试样在650℃下进行不同试验时间节点的蒸汽氧化试验,采用光学显微镜、扫描电镜和X射线衍射等分析方法研究了氧化层的形貌、成分和相组成.结果表明:在试验时间内,不同的S30432钢管试样的抗蒸汽氧化性能存在差异;细化晶粒及提高晶粒度均匀性有利于提高S30432钢的抗蒸汽氧化性能;喷丸处理能改变钢管试样的内壁表面状态,加快Cr从基体向内壁表面扩散,形成富Cr的致密氧化层,显著降低了氧化膜的生长速度;在蒸汽氧化过程中形成的氧化层分内外两层:内层富Cr,与基体界面处形成高铬含量愈合层,外层为铁的氧化物.

Steam oxidation test of various time durations was carried out for S30432 steel tube samples with different grain sizes and surface states using a self-designed device at 650 ℃.Morphology,composition and phase structure of the steam oxide layer were characterized by means of optical microscope（OM）,scanning electron microscope（SEM）,and X-ray diffraction（XRD）.Results show that different S30432 steel samples have different resistance to steam oxidation and that refined and uniform grains are beneficial to improvement of steam oxidation resistance.Shot blasting changes the surface state of inner wall,enhances the diffusion of Cr from matrix to inner surface,forms dense Cr-rich oxide layer,and thus reduces the growth of oxide layer;two oxide layers form during steam oxidation.The internal layer is rich in Cr containing a chromium-richest healing layer at the matrix interface,while the external layer is composed of iron oxides.