锆合金表面Cr/Al复合涂层制备及其1300℃高温蒸汽氧化行为

Preparation of Cr/Al composite coating on zirconium alloy surface and its high temperature steam oxidation behavior at 1300 ℃

采用电镀Cr+热浸镀Al两步法在Zr-4合金表面成功制备了Cr/Al复合涂层。采用电子背散射衍射(EBSD)、扫描电镜(SEM)、透射电镜(TEM)以及X射线衍射(XRD)等对涂层基体组织、表界面形貌、微观结构和物相进行了表征;采用划痕试验和压扁试验分析了涂层的结合性能;在90%湿度1300℃蒸汽条件下对涂层样品进行了高温氧化试验。结果表明:制备的涂层为纯Al层、不同原子比的Al_(x) Cr_(y)合金过渡层和电镀Cr层的多层结构;740℃×3 min热浸镀制备的涂层致密、表面质量好,热浸镀过程对基体组织影响较小;制备的涂层在30%压下量压扁过程中未发生起皱、撕裂和剥落,涂层结合性能较好,其界面结合强度约90 N;在1300℃/90%湿度蒸汽氧化过程中,涂层表层生成了致密α-Al_(2) O_(3)氧化层阻碍了进一步氧化过程,涂层未出现横向裂纹、氧化分层以及基底氧化现象,制备的涂层显示出比锆合金更优的抗蒸汽氧化性能,其氧化增重仅为锆合金的20%左右。

Cr/Al composite coating was successfully prepared on Zr-4 alloy surface by two steps of electroplating Cr and hot dipping Al.Zr alloy matrix microstructure,surface and interface morphology,microstructure and phase of the coating were characterized by means of electron back-scattered diffraction(EBSD)technique,scanning electron microscopy(SEM),transmission electron microscopy(TEM)and X-ray diffraction(XRD).The bonding performance of the coating was analyzed by surface scratch test and coating tube flattening test.The high temperature oxidation test of the coating samples was carried out under the steam condition of 90%humidity and 1300℃.The results show that the prepared coating has a multilayer structure,which consists of pure Al layer,Al_(x) Cr_(y) alloy transition layer with different atomic ratio of Al/Cr and electroplated Cr layer.The coating prepared by hot dipping at 740℃for 3 min is compact and has good surface quality.The hot dipping process has little effect on microstructure of the Zr alloy matrix.The prepared coating tube sample has no wrinkling,tearing and peeling in the process of flattening with 30%reduction.The coating has good bonding performance,and its interfacial bonding strength is about 90 N according to the coating surface scratch test.In the process of steam oxidation at 1300℃with 90%humidity,a denseα-Al_(2) O_(3) oxide layer on the surface layer of the coating is formed and hinders the further oxidation process.There is no transverse crack,oxidation delamination and substrate oxidation in the coating.The prepared coating shows better steam oxidation resistance than Zr alloy,and its oxidation mass gain is only about 20%of that of Zr alloy.