摘  要:高铬铸铁因为它优秀的材料性能在金属冶炼、铝业、加工制造、煤炭生产等大量行业得到非常普遍的应用。氧化铝精炼厂的拜耳精炼过程中的浆料泵组件和管道通常就会用到高铬铸铁，因为高铬铸铁具有高耐磨性。由于拜耳工艺溶液是高度碱性的，所以高铬铸铁需要在碱性环境下具有一定的耐腐蚀性。当前对高铬铸铁的耐磨性、性能与组织的研究均较多，对高铬铸铁的耐腐蚀性的研究较少。

本研究采用药芯焊丝自保护明弧堆焊方法制备了系列高铬铸铁堆焊合金，借助电子显微镜、扫描电镜、M283恒电位仪等仪器研究了Nb在高铬铸铁型堆焊合金中的作用，分析了Nb含量对堆焊合金微观结构和对其耐腐蚀性能的影响。结果表明含Nb的高铬铸铁堆焊合金中有NbC产生，过共晶高铬铸铁的碳化物被明显细化。随着Nb含量的增加，初生碳化物逐渐细化。Nb细化过共晶高铬铸铁的原理为：NbC可能作为初生碳化物的异质形核质点；未形核的NbC颗粒阻碍初生碳化物的长大；生成NbC的反应消耗一部分C而降低过共晶高铬铸铁的过共晶程度。

根据腐蚀后试样的极化曲线发现增大高铬铸铁堆焊合金中Nb的含量，可以显著降低阳极溶解速率，提高其自腐蚀电位。通过对腐蚀后试样的微观形貌观察，发现高Nb含量的试样，其表面的腐蚀坑越细少。研究结果表明提高药芯焊丝中Nb元素的含量有助于提升高铬铸铁堆焊合金的耐腐蚀性能。

关键词：过共晶；高铬铸铁；耐腐蚀性；碳化铌；细化

Abstract:High-chromium cast iron has been widely used in metal smelting, aluminum, manufacturing, coal production and other industries because of its excellent material properties. High chromium cast iron are also usually used in slurry pump components and pipes in the Bayer refining process of Alkaline refineries, because of the high wear resistance of high chromium cast iron. As the Bayer process solution is highly alkaline, so high-chromium cast iron in the alkaline environment requires a certain degree of corrosion resistance. At present, the wear resistance, properties and organization of high chromium cast iron are all studied, and the study about the corrosion resistance of high chromium cast iron is less.

In this study, a series of high chromium cast iron surfacing alloys were prepared by self-shielded arc welding method. The effect of Nb on high chromium cast iron surfacing alloy was studied by means of electron microscope, scanning electron microscope and M283 potentiostat. The effects of Nb content on the microstructure of the surfacing alloy and its corrosion resistance were analyzed. The results show that there are NbC in the high chromium cast iron surfacing alloy containing Nb, and the carbides of hypereutectic high chromium cast iron are obviously refined. With the increase of Nb content, the primary carbides gradually refined. The principle of Nb to refine hypereutectic high chromium cast iron is that NbC may act as a heterogeneous nucleation point of primary carbides; untagged NbC particles block the growth of primary carbides; the reaction to generate NbC consumes a portion of C to reduce the degree of hypereutection of hypereutectic high chromium cast iron.

According to the polarization curve of the corrosion specimen, it is found that increasing the content of Nb in the high chromium cast iron surfacing alloy can significantly reduce the rate of dissolution of the anode and improve its corrosion potential. By observing the microstructure of the sample after corrosion, it is found that corrosion pits on the surface of the sample with high Nb content is less. The results show that improving the content of Nb in the flux cored wire can improve the corrosion resistance of the high chromium white cast iron surfacing all.

Key words：Hypereutectic；High chromium cast iron；Corrosion resistance；Niobium carbide；Refinement