Industrialization of Ni-μSiC electrodeposition on copper moulds for steel continuous casting

Copper moulds usually used for steel continuous casting suffer from severe wear at relatively high temperatures and low friction loads. The more severe solid friction occurs at about 10-40cm distance from the meniscus, depending on the process parameters, where the temperature is about 300-350°C. The copper moulds have been traditionally coated with hard chromium and actually also with thick nickel deposits even if they present lower wear resistance. The aim of this work was the development of a composite Ni-μSiC electrodeposit with higher hardness and wear resistance than the pure nickel using the existing plating bath and commercially available SiC micro-powders. Different types of SiC micro-particles have been purchased and Ni-μSiC deposits have been produced and analyzed, initially, in laboratory scale to evaluate the ability of the powders to be codeposited into the nickel matrix. After the choice of the SiC powder and the determination of the plating parameters a pilot 6000 lt plating tank has been equipped with a system of Venturi pumps in order to maintain the particles in suspension. Preliminary tests have been performed in industrial scale to evaluate the process parameters such as anode-cathode distance, applied voltage, plating time and pumps positioning effect onto the SiC content and its distribution in the nickel matrix. The produced specimens have been observed by Metallographic microscope and Scanning Electron Microscope in cross section to evaluate the SiC content and the microstructure of the nickel matrix. Vickers microhardness measurements have been also performed in cross section and revealed that the co-deposition of the SiC micro-particles leads to a microhardness increase of about 180%. Wear tests at both room temperature and at 350°C have been performed on pure nickel deposits and composite nickel deposits and the wear tracks have been analyzed using both a profilometer and SEM to determine the wear both coefficient and mechanism of each coating. The testing results revealed that the developed Ni-μSiC deposit exhibits a much higher wear resistance in comparison to pure nickel deposits at high temperature and the production process can be easily transferred in industrial scale with slight modifications of the existing deposition plants. Real scale copper moulds have been finally coated with Ni-μSiC composite deposits and are presently under testing in actual working conditions at a steel producing plant.