无金属粘结相TiCN基金属陶瓷在NaOH溶液中的电化学腐蚀行为

Electrochemical corrosion behavior of binderless TiCN-based cermets in NaOH solution

采用放电等离子烧结技术制备TiC_(0.4)N_(0.6),TiC_(0.7)N_(0.3),TiC_(0.7)N_(0.3)-29WC-12TaC和TiC_(0.7)N_(0.3)-29WC-12TaC-2Mo_2C等4种无金属粘结相金属陶瓷,材料的相对密度≥98.5%;扫描电镜观察结果表明,TiC_(0.4)N_(0.6)金属陶瓷的晶粒较其它3种的晶粒明显粗大。采用动电位极化曲线和电化学阻抗谱,研究4种材料在浓度为0.1 mol/L的NaOH溶液(pH=13)中的电化学腐蚀行为。结果表明,4种材料在NaOH腐蚀介质中的耐腐蚀性排序为TiC_(0.7)N_(0.3)>TiC_(0.7)N_(0.3)-29WC-12TaC>TiC_(0.7)N_(0.3)-29WC-12Ta C-2Mo2C>TiC_(0.4)N_(0.6);原料中氮含量增加和金属碳化物的添加均会导致金属陶瓷耐腐蚀性能降低;在一定条件下,无金属粘结相的TiCN金属陶瓷材料在碱性介质中可形成含氧化合物的表面钝化膜,导致腐蚀过程中出现伪钝化现象。4种无金属粘结相TiCN金属陶瓷材料中,TiC_(0.7)N_(0.3)的耐腐蚀性能最优,相对密度最高,达到99.5%。

Four binderless TiCN-based cermets TiC0.4N0.6,TiC0.7N0.3,TiC0.7N0.3-29WC-12TaC and TiC0.7N0.3-29WC-12TaC-2Mo2C with a relative density greater than 98.5%were prepared by spark plasma sintering(SPS).Scanning electron microscopy SEM observation shows that the average grain size of binderless TiC0.4N0.6 is substantially larger than that of other three groups.Electrochemical corrosion behaviors of binderless TiCN-based cermets in 0.1 mol/L NaOH solution were investigated by potentiodynamic polarization curve and electrochemical impedance spectroscopy.The results show that the corrosion resistance of the cermets in NaOH solution follows the following order,i.e.,TiC0.7N0.3>TiC0.7N0.3-29WC-12TaC>TiC0.7N0.3-29WC-12TaC-2Mo2C>TiC0.4N0.6.The increase of nitrogen and the addition of metal carbides are detrimental to the corrosion resistance of cermets.The oxidation product formed during the corrosion process can act as a passivation film,which results in a pseudo-passivation phenomenon.Binderless TiC0.7N0.3 cermet has the highest relative densification(99.5%)and the best corrosion resistance.