一种新型Ni-Fe-Cr基合金在模拟锅炉烟气中的腐蚀行为研究

The Corrosion Behavior of a Newly Developed Ni-Fe-Cr Based Alloy in Simulative Flue Gas Environment

应用X射线衍射仪、扫描电子显微镜、能谱仪等分析方法研究一种新型Ni-Fe-Cr基高温合金在700℃/750℃煤灰/烟气中的腐蚀行为。结果表明:750℃的腐蚀速率明显高于700℃,其腐蚀层的厚度由700℃的3μm增加到20μm。腐蚀1 000h后,SEM观察到Ni-Fe-Cr高温合金在700℃下表面有少量"瘤状"凸起产物,XRD结合EDS表明其腐蚀产物由表向里依次是结构疏松的NiO、Fe_2O_3和Fe3O4,内层为相对致密的Cr_2O_3、Al_2O_3和TiO2,基体和腐蚀层界面靠近基体一侧是多孔的硫化物。提高腐蚀温度到750℃表面出现更多凸起,并且出现了破裂。Cr_2O_3保护性氧化膜局部开裂或者剥落而形成"瘤状"凸起产物。氧化膜生长过程中的内应力以及温度降低产生的热应力共同作用,导致氧化膜开裂甚至与基体剥离。温度升高同样加剧熔融盐破坏氧化膜从而加快腐蚀进程。

The corrosion behavior of a newly developed Ni-Fe-Cr based super-alloy was investigated in coal ash/flue gas environment at 700℃/750℃respectively by means of X-ray diffraction(XRD),scanning electron microscope(SEM),and energy dispersive spectrometer(EDS).The results indicated that the corrosion rate at 750℃was higher than that at 700℃obviously,and the corosion product layers became thicker from 3μm to 20μm.A few“bulges”were detected on the surface of Ni-Fe-Cr based alloy after corrosion for 1 000 h at 700℃.XRD and EDS showed that the corrosion products from the surface to inside were composed of loose structure of NiO,Fe 2O 3 and Fe 3O 4,while the inner oxides were relatively dense Cr2O3,Al2O3 and TiO2.The interface between the oxide film and the matrix was sulfide with pore structure.Increasing the temperature to 750℃,a large number of bulges were detected on the top surfuce,and some of them cracked.The cracking or spalling of Cr2O3 film in the local area was the reason why“bulges”corrosion products formed.The internal stress during the growth of oxide film together with the thermal stress in the cooling process can result in rupture of oxide film or even spilling from the base alloy.Rising the temperature also accelerated salt melting to break the local film and quicken Ni-Fe-Cr based alloy′s corrosion rate.