Mo含量对Ti(C,N)基金属陶瓷在H_2SO_4溶液中腐蚀性能的影响

Effect of Mo Content on Corrosion Resistance of Ti(C,N)-based Cermets in H_2SO_4 Solution

本文以四种不同Mo含量的Ti(C,N)基金属陶瓷为研究对象,通过组织观察、孔隙率测定、抗弯强度、硬度测试方法研究了Mo含量的变化对Ti(C,N)-Ni金属陶瓷组织和性能的影响,试验结果表明:Ti(C,N)基金属陶瓷呈现典型的芯-环结构,随Mo添加量增加,晶粒发生明显细化,抗弯强度及硬度增加。通过电化学测试方法,如动电位极化、交流阻抗曲线测定(EIS)、静态浸泡腐蚀试验等方法,结合腐蚀形貌观察,研究了不同Mo含量对Ti(C,N)基金属陶瓷在0.2 mol/L H2SO4溶液中的电化学性能和腐蚀性能的影响规律。含有Mo的Ti(C,N)-Ni金属陶瓷的极化曲线存在两个钝化区,其中一个为"伪钝化"区,随Mo元素含量增加,其维钝电流密度减小,维钝区间扩大。交流阻抗试验显示,Ti(C,N)-Ni金属陶瓷的反应阻抗值会随着Mo含量的增加而变大。Ti(C,N)-Ni金属陶瓷在试验溶液中的腐蚀速率也会随Mo含量的增加而明显下降。主要原因是由于随着Mo添加量的增加,降低陶瓷的孔隙率,增大了材料的致密度,改善了硬质相和粘结相之间的润湿性;而且溶解于粘结相中的Mo含量提高,提高了粘结相的耐蚀性,从而降低了金属陶瓷在H2SO4溶液中的腐蚀速率。

The effects of Mo content on the microstructures and properties of four types of Ti（C,N）-based cermets with different Mo content were studied through microstructure observation as well as porosity, transverse rupture strength and hardness tests. The results indicate that the Ti（C,N）-based cermets represent typical core-rim structure, the grains have an obvious trend to become fner with the increase of Mo content, and the transverse rupture strength and hardness are also enhanced. The electrochemical characteristics and corrosion resistance of the Ti（C,N）-based cermets in H2SO4 solution were investigated via electrochemical methods such as potentiodynamic polarization, electrochemical impedance spectroscopy （EIS） and static immersion corrosion tests combined with the observation of corrosion micrographs. It is found that the polarization curve of the tested Ti（C,N）-Ni cermets has two typical passivation regions, wherein a pseudopassive region exists, the passivation current is reduced and the passivation range is enlarged with the increase of Mo content. The EIS results also demonstrated that the impendence of the reaction rises with the increase of Mo content. Moreover, the corrosion resistance of the eermets in the tested solution is improved, it mainly due to higher Mo addition decreases the porosity of the cermets, the compactness of the cermets is increased, the wettability between the ceramic phase and the binder phase is enhanced; the content of Mo dissolving in the binder phase is increased, thus the corrosion resistance of the binder phase is improved, and the corrosion rate of the cermets in the H2SO4 solution is slow down.