Nb对铸造双相耐热钢高温氧化的影响

Effect of Nb on high temperature oxidation behavior in cast duplex heat-resistant steel

为探究Nb对双相耐热钢高温抗氧化性能的影响规律,采用扫描电镜、能谱分析和XRD等分析测试手段研究了1 000和1 100℃下含Nb双相耐热钢高温氧化性能。结果表明,双相耐热钢氧化层结构为氧化外层(MnCr_2O_4)→氧化内层(Cr_2O_3)→Si的内氧化层;Nb的加入加速双相耐热钢的表层氧化膜生长,降低了其抗氧化性能;随着Nb含量的增加,表层基体内部形成富Nb相,促进Si的沿晶界氧化而抑制Si的界面氧化,Cr_2O_3层和Si的内氧化层厚度均增加。在对高温抗氧化性能要求高的情况下,本双相耐热钢中Nb的质量分数应控制在0.8%以下。

In order to research the effect of Nb on the high temperature oxidation resistance of duplex heat-resistant steel,the high temperature oxidation performance of Nb-containing duplex heat-resistant steel at 1 000 and 1 100℃was investigated by scanning electron microscopy,energy spectrum analysis and XRD.The results show that the oxidation layer of duplex heat-resistant steel is composed of oxidized outer layer(MnCr2O4)→oxidized inner layer(Cr2O3)→inner oxide layer of Si;the addition of Nb accelerates the growth of surface oxide scale of duplex heat-resistant steel,while oxidation resistance is deteriorated.With the increase of Nb content,Nb-rich phase is formed in the surface matrix,which promotes oxidation along the grain boundary of Si and inhibits the interfacial oxidation of Si,and the thickness of Cr2O3 layer and inner oxide layer of Si increases.To meet higher requirements of high temperature oxidation resistance,the Nb content in the duplex heat-resistant steel should be below 0.8%.