Electrodeposition behavior and wear resistance of Co-Ni alloys from sulfamate baths for continuous steel casting mold

Electrodeposition behavior of Co-Ni alloys, which has been applied in the c oating of continuous steel casting mold was studied by measuring the polari zation curves using a Cu substrate in sulfamate baths of various compositio ns at 55 degrees C under galvanostatic conditions. The wear resistance of e lectroplated Co-Ni film was also investigated by sliding wear test of ring- on-plate type at 300 degrees C. The results obtained were as follows : ( 1) In a wide range of bath composition, Co-Ni alloy deposition shows a fe ature of anomalous codeposition in which the less noble Co is electrodeposi ted in preference to Ni. The Ni deposition is greatly polarized when compar ed to the Co deposition From their single baths. Therefore, Co is deposited in preference to Ni, though Ni deposition from the alloy plating bath is m ore largely depolarized than that from its single bath. ( 2) The wear resistance of Co-Ni coating is improved with increasing Co co ntent more than 50% in the deposits. The higher Co content in the deposit i s, the thicker oxide film mainly composed of CoO and Co3O4 is formed on the surface of Co-Ni coating, which improves sliding property to prevent adhes ive wear between Co-Ni coating and press ring.