回火温度对Cr7钢耐CO_(2)腐蚀性能的影响

Effect of Tempering Temperature on CO_(2) Corrosion Resistance of Cr7 Steel

利用高温高压釜加速腐蚀试验,获得了Cr7钢经不同回火处理后在CO_(2)环境中的静、动态腐蚀速率,并利用SEM结合XRD分析了样品的组织及腐蚀产物类型。结果表明,Cr7钢经不同温度回火后的组织均为回火马氏体,其耐蚀性能随着回火温度的升高呈下降趋势,静态腐蚀产物为Cr(OH)_(3)和FeCO_(3),动态腐蚀膜表面还附着由FeCO_(3)和CaCO_(3)组成的颗粒物。扫描开尔文探针和电子背散射衍射分析结果显示,经200℃和500℃回火后的样品电位差约为80 mV,600℃回火后的样品电位差增大到了118 mV。回火过程中马氏体板条的合并使得大角度晶界的比例升高,从而使微区电位起伏加大,这是引起Cr7钢耐蚀性能下降的主要原因。

The static and dynamic corrosion rates of Cr7 steel after different tempering treatment in CO_(2)environment were gained by high temperature autoclaving to accelerate corrosion tests.The microstructure and corrosion products of the samples were analyzed by SEM and XRD.The results show that the microstructure of Cr7 steel after tempering at different temperatures was tempered martensite,and the corrosion resistance decreased with the increase of tempering temperature.The static corrosion products were Cr(OH)_(3)and FeCO_(3),and the dynamic corrosion film surface was also attached with particles composed of FeCO_(3)and CaCO_(3).The results of scanning Kelvin probe and electron backscatter diffraction analysis showed that the potential difference of the sample after tempering at 200℃and 500℃was about 80 mV,and the potential difference of the sample after tempering at 600℃increased to 118 mV.The merging of martensite laths during the tempering process leads to an increase in the proportion of high-angle grain boundaries,which leads to increased micro-region potential fluctuations,which is the main reason for the decline of the corrosion resistance of Cr7 steel.