热镀锌沉没辊的耐锌腐蚀失效过程

采用超音速火焰喷涂技术在316L不锈钢基体上制备WC-12Co涂层,并测试其在430℃锌液中的耐腐蚀性,分析沉没辊的腐蚀机理以及失效过程。采用SEM、EDS和XRD分析了腐蚀前、后涂层表面显微结构、化学成分及其相组成的变化。结果表明,WC-12Co粒子之间通过高速碰撞发生强烈的塑性变形而结合在一起,涂层内部致密性很好,喷涂过程中没发生明显氧化现象;涂层的显微硬度平均为1 215HV0.2,结合强度达到85MPa;无涂层试样在腐蚀59h后直径减少20%;经过10天的浸锌试验后,涂层开始产生均匀性腐蚀,涂层中的Co基体受液锌腐蚀生成Co5Zn21化合物,涂层开始遭到破坏;经过15天浸锌试验后,部分锌液穿过涂层与基体中的Fe化合生成FeZn13(即锌渣),涂层局部开始脱落,涂层失效开始。

Zinc Corrosion Resistance and Inactivation Process of Sink Roll in Hot Galvanization

The WC-12Co coatings were sprayed by high velocity oxyfule spraying(HVOF) on 316L stainless steel.The corrosion resistance was tested at 430 ℃ and the inactivation process of the sink roll was studied.The changes of microstructure,chemical composition and phase constituent during the corrosion process were analyzed by SEM,EDS and XRD.The results show that the WC-12Co coating is deposited through intensive plastic deformation of the spray particles by high-speed impact,and no oxidation phenomena is discovered in the spray process.The average of microhardness and bond strength of the coating attained 1 215 HV0.2 and 85 MPa respectively.The diameter of non-coating samples decreased by 20% after corrosion of 59 h.The coating started to corrode uniformity after 10 days.Co5Zn21 compounds were generated when Co based metal was corroded by liquid Zinc and the coating was distroied.After 15 days,FeZn13 was generated with Fe in base material when part of liquid Zinc went through the coating.Part of the coating fell off and the failure began.